ZSE Aviation Forecast Discussions

045 FXUS66 KSEW 182307 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 307 PM PST Mon Nov 18 2024 .SYNOPSIS...Troughing will maintain rain and mountain snow showers across western Washington that will diminish tonight. The next system will rapidly develop on Tuesday, spreading strong winds inland Tuesday afternoon into Wednesday morning alongside lowland rain and mountain snow. An active pattern is favored to continue through the rest of the week with low pressure offshore. && .SHORT TERM /TONIGHT THROUGH THURSDAY/...Upper level troughing will continue over western Washington, allowing for continued shower activity through Tuesday morning. Snow levels will generally stay between 1000-2000 feet with light rain amounts over the lowlands and lessening snow totals over the mountains. Cloudy skies will give way to some sun breaks this afternoon, with highs in the mid to upper 40s today for the lowlands. Some clearing of cloud cover over the mountains overnight may also allow for some locations in the southwest interior to dip near freezing overnight, with some rain snow mix shower activity in the early morning hours over some of the higher hills. An anomalously strong surface low will continue to intensify offshore on Tuesday, bringing significant weather to western Washington. The following impacts are listed below: * STRONG WINDS: Intense pressure gradients will cause strong east winds to develop Tuesday afternoon through Wednesday morning. Areas along the Pacific Coast and along the Cascade Foothills will see gusts up to 65 mph. Areas elsewhere will see gusts up to 50 mph. Most area waters are favored to see Storm Force winds. The strongest winds will occur Tuesday evening into the early morning hours Wednesday. Significant impacts may occur at lower-than-usual wind speeds due to the atypical easterly wind direction. * BLIZZARD CONDITIONS: Strong winds in combination with moderate mountain snow will impact travel through the Cascade Passes, where gusty winds will likely cause periods of whiteout conditions. The strongest impacts will occur Tuesday evening through early Wednesday morning when east winds will be strongest. Precipitation accompanied by strong winds will spread across western Washington by Tuesday evening as a front lifts across the area. Snow levels will rise to 2500-3500 feet into early Wednesday, and easterly gap winds will allow snow levels through the Cascade Passes to be slightly higher. Despite higher snow amounts on the eastern slopes of the Cascades, a Blizzard Warning has been issued for strong winds contributing to periods of whiteout conditions through the Passes. Snow amounts will reach 4 to 12 inches above 2500 feet through Wednesday morning, with locally higher amounts over the highest peaks. The upper level low will weaken and retrograde on Wednesday, sliding another front across the area. This will cause conditions to destabilize and change stratiform precipitation over to showers, which are on track to continue throughout the day Wednesday. Snow amounts will lighten over the mountains, and precipitation will continue across the lowlands that will measure up to half an inch of rainfall through Wednesday. Rainfall amounts will be higher over the Olympic Peninsula, where rain totals along the coast will reach 1 to 2 inches. A longwave upper low will remain off the coast on Thursday, spreading another impulse northward across the region that will maintain widespread shower activity. Snow levels will rise above 3000-4000 feet with an additional few inches of snow accumulation across the mountains. Rainfall amounts will be lighter across the lowlands. .LONG TERM /FRIDAY THROUGH MONDAY/...Model solutions start to split heading into the weekend, though ensemble consensus maintains unsettled conditions across the region through Monday. Troughing offshore is favored to shift inland towards the end of the weekend, but the exact timing and placement of any fronts is uncertain at this time. Ensembles favor light snow accumulations across most of the Cascade Passes each day through the weekend and into early next week. 15 && .AVIATION...Zonal flow aloft as broad troughing briefly moves through the region, with a weak shortwave ridge building through western Washington this afternoon. Cigs are mixed between MVFR and VFR this afternoon, but the trend is generally for MVFR cigs to last overnight and into tomorrow morning. Surface winds will be out of the south to southwest at 5 to 8 kt. The bigger forecast challenge will come tomorrow afternoon as a strong area of low pressure off shore nears the coast and generates strong easterly wind across the majority of western Washington. North to south oriented runways may face challenges with crosswinds Tuesday night into early Wednesday morning. Additionally, there is a possibility for a subtle ridgetop inversion in the Cascades, which could generate some mountain wave activity that impacts terminals in Puget Sound. Confidence on this scenario is low (less than 20 percent), but it is something to be aware of. The winds will begin subsiding by 12Z on Wednesday. Though the main headlines of this storm will be wind, there will also be some rain with it and the combination could lead to varying levels of visibility and ceilings. KSEA...MVFR at the terminal this afternoon, with these conditions likely to persist through the overnight hours. Wind speeds have been from the south to southwest at 10 kt, with the occasional gust to 15 kt. Expect some showers to linger in the vicinity after 06Z, but there could be a period of VFR cigs tomorrow morning. Winds will begin to veer easterly after 18Z tomorrow as the next storm system impacts the area. Easterly wind speeds of 20 to 25 kt with gusts over 35 kt are likely through early Wednesday morning. As mentioned above, the possibility for mountain wave activity impacting Puget Sound terminals exists, but confidence is low. Kristell && .MARINE...A strong and expansive area of low pressure, around 960 mb, will impact the area and its waters beginning tomorrow afternoon and last into Wednesday morning. Here are the key points for the marine forecast: * Seas: Seas will remain elevated now until Tuesday afternoon, with Small Craft Advisories for such conditions changing over to Storm Warnings to reflect the onset of the strong easterly winds. Seas over the outer coastal waters may reach heights of 25 to 30 feet, with 12 to 18 ft seas closer to the Washington coastline. The Storm Warning also extends to the Strait of Juan de Fuca where the winds could generate seas of 8 to 11 feet. * Wind: The onset of the strongest winds over the waters will begin late Tuesday morning, and intensify through the afternoon and evening. Winds associated with the storm warning call for gusts of 65 kt with sustained speeds of 40 to 45 kt. Similar speeds are forecast for the Strait of Juan de Fuca. The Northern Inland waters have Gale Warnings posted and Puget Sound will face an upper end Small Craft Advisory. The easterly direction of the wind limits the amount of alignment needed throughout Puget Sound to cause further impacts. * Grays Harbor Bar: Rough bar conditions will linger throughout the duration of this storm, but with an extra consideration on the unusual east wind. Combined with the ebbs and heightened seas on the immediate coast, conditions are likely to remain hazardous across the bar. In the wake of this system, seas will be slow to calm, but 10 ft seas or less will finally be achieved on Thursday. Kristell && .HYDROLOGY...Precipitation over the Olympics Tuesday night into Wednesday could push the already running high Skokomish above flood stage Wednesday. Snow levels down to around 2000 ft during the heaviest precipitation could limit the runoff and any flooding chance. The flood watch for Mason county will continue. Rises also forecast for the remainder of the rivers this week but the combination of relatively low snow levels and the lack of heavy mountain precipitation will keep rivers in their banks. Felton/Bower && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Wind Advisory from 2 PM Tuesday to 4 AM PST Wednesday for Admiralty Inlet Area-Bremerton and Vicinity-Eastern Strait of Juan de Fuca-Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley Area-San Juan County-Seattle and Vicinity- Southwest Interior-Tacoma Area-Western Skagit County- Western Whatcom County. Flood Watch from late Tuesday night through Wednesday afternoon for Hood Canal Area-Lower Chehalis Valley Area-Olympics. Winter Weather Advisory from 4 PM Tuesday to 4 PM PST Wednesday for Olympics. High Wind Warning from 2 PM Tuesday to 4 AM PST Wednesday for Bellevue and Vicinity-Central Coast-East Puget Sound Lowlands-North Coast-Western Strait of Juan De Fuca. Blizzard Warning from 4 PM Tuesday to 10 AM PST Wednesday for West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes. PZ...Small Craft Advisory until 10 AM PST Tuesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-Grays Harbor Bar. Small Craft Advisory from 4 PM Tuesday to 1 AM PST Wednesday for Grays Harbor Bar. Small Craft Advisory until 4 PM PST this afternoon for West Entrance U.S. Waters Strait Of Juan De Fuca. Storm Warning from 10 AM Tuesday to 10 AM PST Wednesday for Central U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance U.S. Waters Strait Of Juan De Fuca. Gale Warning from 4 PM Tuesday to 4 AM PST Wednesday for Northern Inland Waters Including The San Juan Islands. Small Craft Advisory from 4 PM Tuesday to 4 AM PST Wednesday for Admiralty Inlet-Puget Sound and Hood Canal. && $$

293 FXUS66 KPQR 182353 AFDPQR Area Forecast Discussion National Weather Service Portland OR 353 PM PST Mon Nov 18 2024 .SYNOPSIS...Scattered showers continue across the area tonight, with lingering winter weather impacts in the Cascades. A powerful system approaches the coastal waters on Tuesday, bringing strong winds to the coast and breezy conditions to the interior valleys Tuesday evening through early Wednesday morning. This system will also bring another round of heavy snow to the High Cascades. Wet weather continues through the end of the week, but the probability for significant hydro impacts has diminished with time as a strong atmospheric river remains south of the area. && .DISCUSSION...Scattered rain showers are ongoing across the area this afternoon in moist onshore flow behind a departing shortwave trough, with locally heavy snow showers continuing above 2000 feet. Have received reports today of some wet snow mixing in with heavier rain showers all the way down to 700 feet elevation, with no accumulation. Showers will linger across the area through tonight in the wake of the departing trough. The Winter Weather Advisory for the higher points of the Coast Range should be allowed to expire at 10 PM this evening, but may need to consider extending the winter weather headlines for the Cascades a bit longer overnight depending on observed trends with respect to shower coverage and intensity. Also can`t rule out a few rumbles of thunder at lower elevations through this evening, but thunder chances will gradually diminish with time and mainly favor the coastal waters overnight. Attention quickly turns to a powerful system developing over the NE Pacific tonight and approaching our region on Tuesday. Water vapor imagery currently depicts a broad upper level trough centered over the Gulf of Alaska, with a 150 kt jet streak rounding the base of the trough. A baroclinic leaf noted crossing 150W signals imminent development of a surface low pressure system, and this feature will undergo explosive cyclogenesis over the next 24 hours beneath the left exit region of the upper level jet. Models are in good agreement in depicting a sub 950 mb low approximately 350-400 miles off the Washington coast by late tomorrow afternoon, sending a Storm Force front through the coastal waters during the evening. Wind is obviously the primary forecast concern with this system, and have upgraded the watches to High Wind Warnings along the coast beginning 4 PM tomorrow and continuing through early Wednesday morning. Forecast details will be tricky as the pressure gradient retains an offshore component until the front reaches the coast, which would tend to restrict the strongest winds to the immediate coast, however very strong winds of 80-90 kt depicted by the models at 925 mb leave open the possibility for a higher end wind event if any of those winds are able to mix down to the surface as the front moves onshore. For now, still expecting maximum gusts around 60 mph at the coast, but hi-res guidance does show around a 25% probability for gusts as high as 70 mph and a 10% chance for gusts as high as 80 mph on the central Oregon Coast, with this most likely to occur roughly 4-10 PM Tuesday evening. Also opted to issue a Wind Advisory for the Willamette Valley and the interior valleys of southwest Washington. While winds will not be as strong as those seen at the coast, hi-res models do indicate around a 50% chance for winds to gust as high as 45 mph in the valleys as the front moves through Tuesday evening into early Wednesday morning. The front will also bring another burst of locally heavy rain and mountain snow Tuesday night into Wednesday, with the latest forecast calling for around 0.75-1.25" of rain at the coast and around another half inch inland through early Wednesday. Issued another Winter Weather Advisory for the High Cascades Tuesday afternoon through Wednesday morning. Snow levels will initially be around 2500-3000 feet at onset of precipitation on Tuesday but will quickly rise above 4000 feet Tuesday evening. Therefore expect the highest additional snowfall amounts of 8-14 inches to be mainly confined to the passes and above for this event. Strong winds associated with the front will also lead to some blowing snow concerns, but relatively heavy, wet snow with temperatures in the low 30s will not be conducive to true blizzard conditions. Nonetheless, travel will be very difficult with heavy snow and severely reduced visibilities at times. As for the previously advertised atmospheric river event, models have continued to depict that feature shifting south of the area, with the heaviest rain focused over southwest Oregon and northern California through the middle of the week. As such, model QPF has continued to trend downward with the latest runs. The current middle ground solution would give the coast around 4 inches of rain for the 72 hour period ending Friday morning with around 1.50-2.00" in the Willamette Valley, while a reasonable worst case as depicted by NBM 90th percentile guidance would bring 5-6 inches to the coast and 2-3" in the valley. Flood guidance has continued to trend downward as a result, with no area rivers currently forecast to reach flood stage and HEFS guidance giving around a 10-20 percent chance of reaching minor flood stage on the more responsive rivers draining the Coast Range. While some local ponding of water and drainage issues can be expected, the bottom line is the the probability for significant hydro impacts this week continue to trend downward as QPF amounts trend down with recent model runs. /CB The wet weather looks to continue into the weekend with ensembles showing the potential for a weaker weather system Saturday. Details still remain uncertain at this time after Wednesday. Will need to keep an eye on how models resolve the complicated features of the forecast. -HEC && .AVIATION...A mix of VFR/MVFR conditions continues this afternoon with scattered showers continuing across the region. A stabilizing airmass overnight will lead to increasing probabilities for MVFR and IFR conditions to become the dominant flight condition at all TAF sites. Statistical guidance suggests greater than a 80% chance of MVFR conditions at any given hour at nearly every inland TAF site beginning between 06-09z Tuesday and continue through 18z Tuesday. The probability for IFR conditions climb abruptly into the 20-50% starting around 06-09Z but only lasts until 15Z or so. It should be noted that there is a 20-30% chance for a brief thunderstorm, primarily for the coast taf sites through at least this evening. Showers will continue tonight before a strong front approaches and brings a steadier rain through Tuesday. Southwest winds along the coast continue at around 10 kts while winds inland continue from the south at 10-15 kts and a few gusts up to 20 kts. Winds will increase late tonight into Tuesday morning as a strong front approaches. Expect winds along the coast to turn southerly at 20-25 kts and gusts to 35 kts while inland winds increase to 15-20 kts with gusts 25-30 kts from the southeast. PDX APPROACHES...Scattered showers continue through tonight. A stabilizing airmass overnight will lead to increasing probabilities for MVFR and IFR conditions to become the dominant flight condition between 06-09z Tuesday and continue through 18z Tuesday. South to southwesterly winds today will most likely back to easterly between 06-12z Tuesday. Winds expected to increase to 10-15 kts with gusts to 20 kts Tuesday as the front approaches. -Batz && .MARINE...Westerly winds will gradually shift southerly tonight ahead of an approaching cold front. Seas remain steep with heights in the low to mid teens at 13-14 seconds, warranting a Haz Seas Warning. Seas will dip a few feet for the northern zones and the inner water zones, dropping into Small Craft Advisory Criteria this evening through 10 am Tuesday. Conditions become treacherous as a strong storm approaches the waters Tuesday, easily bringing storm force winds from Tuesday afternoon to late Tuesday night. A Storm Warning goes into effect at 10 am Tuesday with gusts between 50-60 kts expected late Tuesday afternoon. Sporadic gusts above 60 kts will also be possible. NBM guidance suggests around a 10-40% chance of Hurricane Force winds (64 kts or higher), for portions of the outer waters while HREF suggests Hurricane Force winds could be more widespread with probabilities 50-70%, with the highest probs across the southern zones. With strong wind waves and swell remaining elevated, seas will be quite high, with current forecasted peak waves at 20-26 ft at 13-15 seconds Tuesday afternoon into late Tuesday night. Sustained winds peak between 40-50 kts with gusts to 60, a few hurricane force gusts (>64 kts) possible during the 1 pm to 7 pm timeframe. Winds expected to fall back into Gale criteria thereafter. -Batz && .BEACH HAZARDS...High sneaker wave threat remains in place through today due to an increasing westerly swell with a dominant wave period around 10-14 seconds. With the Perigean spring tides underway (commonly referred to as "king tides"), it is a good idea to take extra precaution on beaches. Waves can run up significantly farther on a beach than normal, including over rocks and jetties. Sneaker waves can suddenly knock people off of their feet and quickly pull them into the frigid ocean which may lead to serious injury or drowning. The sneaker wave threat looks to remain high through early next week. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...High Wind Warning from 4 PM Tuesday to 4 AM PST Wednesday for ORZ101>103-106-107. Winter Weather Advisory until 10 PM PST this evening for ORZ106-107. Wind Advisory from 4 PM Tuesday to 4 AM PST Wednesday for ORZ108>118. Winter Storm Warning until 10 PM PST this evening for ORZ123>128. Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday for ORZ126>128. WA...High Wind Warning from 4 PM Tuesday to 4 AM PST Wednesday for WAZ201. Wind Advisory from 4 PM Tuesday to 4 AM PST Wednesday for WAZ204>207. Winter Storm Warning until 10 PM PST this evening for WAZ211. Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday for WAZ211. PZ...Hazardous Seas Warning until 7 PM PST this evening for PZZ210- 251>253-271. Small Craft Advisory from 7 PM this evening to 10 AM PST Tuesday for PZZ210-251>253-271. Gale Warning from 10 AM Tuesday to 4 AM PST Wednesday for PZZ210. Storm Warning from 10 AM Tuesday to 4 AM PST Wednesday for PZZ251>253-271>273. Hazardous Seas Warning until 1 AM PST Tuesday for PZZ272-273. Small Craft Advisory from 1 AM to 10 AM PST Tuesday for PZZ272- 273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

536 FXUS66 KMFR 182252 AFDMFR Area Forecast Discussion National Weather Service Medford OR 252 PM PST Mon Nov 18 2024 .SHORT TERM...A cold upper trough is over the area bringing showers. Snow levels are around 3000 feet. Snow showers will continue to bring impacts to higher passes in the Cascades and across western Siskiyou today and into this evening. Shower activity will decrease in coverage and intensity this evening into tonight over the mountains and east side. However, models show another band of precipitation spreading inland from the coast bringing light to moderate showers into the area tonight and Tuesday morning. A moist and powerful front arrives Tuesday afternoon through Wednesday. This is an unusually strong and moist frontal system and there is high confidence for very high wind impacts along the coast and coastal waters (hurricane force wind gusts) and moderate to strong winds affecting inland areas as well. Current Extreme Forecast Index values show a strong signal for abnormally high winds, particularly along the coast and over the coastal waters. Additionally, heavy rain and snow is forecast, with heavy rain along coastal areas, and heavy snow likely in the mountains/higher terrain and Mount Shasta City area. Heavy rain will bring a potential for flooding (especially west of the Cascades for small streams and some mainstem rivers just inland of coastal areas). Heavy snow combined with very strong winds for the mountains will bring potential of trees down and dangerous travel conditions. Additionally, the potential of heavy, wet snow and strong winds in the Mount Shasta City area, including portions of Interstate 5, may create added high impacts for the communities in that area with a potential of power outages, tree damage and significant travel impacts. High wind warnings and wind advisories (NPWMFR) are in effect for much of the area. Winter storm warnings and advisories are in effect for the areas that will see the highest impacts, mainly the Cascades east and across areas in Northern California. Please see the WSWMFR for details. * RAINFALL: Heavy precipitation is likely west of the Cascades, with 2 to 5 inches of rainfall along the coast and into the coastal mountains and across southwest Josephine and western Siskiyou county. 0.75 to 2 inches is likely for valleys in Douglas, northern Josephine, Jackson and central Siskiyou County. Some of this will fall as snow, over the mountains/higher terrain and Mt shasta area. With the heavy precipitation, rapid rises in rivers and small streams are expected. There is a potential for flooding along the Coquille River and flooding for small streams, especially along the coast and into the Umpqua Basin. Please see the ESFMFR for details. * SNOWFALL: Heavy snow is expected to impact the mountains (Cascades, Siskiyous and mountains in Western Siskiyou Co.) and the Mount Shasta City area. Areas of moderate to heavy snow area expected east of the Cascades. Heaviest snow impacts are expected into Siskiyou County, especially for the Mount Shasta area and higher passes in western/southern Siskiyou Co. Heavy, wet snow in the Mount Shasta area may (20% chance) reach over 2 and up to 3 inches per hour at times Tuesday evening through Wednesday morning, when conditions are expected to be the worst. Current forecasts call for 15 to 20 inches of storm total snowfall from near Weed southward to Mount Shasta City and around 6 inches at Dunsmuir. Snow levels will fluctuate though around 2000 to 3500 feet Tuesday evening through Wednesday afternoon. So confidence is moderate on storm total snowfall totals for lower elevations near Mount Shasta. Of concern is that heavy snow and wind may lead to trees down and power outages as well as impassible roads, low visibilities and white out driving conditions at times. Above 3500 feet in western/southern/southeastern Siskiyou County, very heavy snow and strong gusty winds are likely to create high impacts from heavy snowfall around 20 to 30 inches (but locally higher over higher mountains) and low visibilities. Across the Southern Oregon Cascades and Siskiyous, also expect heavy snow with snowfall totals ranging from around 8 to 18 inches and locally up to 2 feet. Exposed higher mountains will also see a potential for strong winds and white out conditions at times, especially Tuesday evening into Wednesday morning. East of the Cascades, expect areas of moderate to heavy snow along with strong gusty winds. This will bring impacts to much of the area with heaviest snow expected north of Chiloquin over northern Klamath County. Travelers are urged to avoid travel during the worst of the storm and for these hard hit areas. Please see the WSWMFR for details. * WINDS through Wednesday...We will see some of the strongest winds we have seen in several years as this storm system passes through the area Tuesday into Wednesday. The system itself is an almost perfect classic scenario for strong winds here in our forecast area: a rapidly deepening surface low approaching or crossing 130 degrees W, concurrent with the cold front passing onshore. Also, the models have been consistent with mean sea level pressure gradients reaching -11 mb between North Bend and Arcata and also between Medford and Redding. Typically, coastal and inland high wind warnings (and marine storm force wind warnings) only need to reach -8, so we are well past this threshold. In addition, model winds at 850mb (a good way to gauge the maximum possible marine and coastal surface wind gust speeds) are approaching 95 kt, which are some of the highest speeds seen at that level in quite some time. Meanwhile at 700 mb (a good measure of maximum gusts over and east of the Cascades), speeds are approaching 75 to 80 kt. In basically every measure we look at when analyzing and forecasting high winds, this storm looks to surpass almost all thresholds, with a few exceptions. * Winds will begin increasing at the coast by Tuesday midday, and will then peak in the evening before gradually diminishing through Wednesday morning. Areas west of the Cascades, including in the Shasta Valley, will follow the same timeline but about 3-6 hours later (peaking in the late evening and overnight), and east of the Cascades about 6 to 9 hours later (generally late Tuesday night but before sunrise Wednesday). * As a result, we have issued numerous wind headlines: High Wind Warning at the coast, in the Shasta Valley, and across the East Side, and Wind Advisories for almost all of the the inland areas west of the Cascades. It should be noted that for the inland areas west of the Cascades, areas of higher terrain or in the southern Rogue River/Bear Creek valley near Ashland may briefly reach High Wind criteria right when the front passes, but confidence on this is lower than the rest of the forecast area as the general wind flow ahead of the front will be from the southwest, and typically need to be out of the south to southeast to result in the higher wind speeds. * Areas along and east of the Cascades, and in the far southern Shasta Valley, will see these winds combining with snow, and this could result in near-whiteout conditions at times due to blowing and drifting snow. For almost all areas, road travel could be difficult due to strong winds, especially if it is a crosswind over roadway and/or if you are in a high profile vehicle. If you intent to travel anywhere in the area during the time of the storm, it is advised to make alternate plans and travel at another time. * It should also be noted that a few model solutions are suggesting the development of a small, weaker surface low to our southwest as the front moves onshore. This would slow down the progression of the system a bit, while also weakening it slightly. The chances of this are low (around 10 to 15 percent) but could result in slightly weaker winds and a later onset than forecast. -BPN Wednesday evening and night, snow levels will rise to 4000 to 6000 feet and heaviest precipitation will shift south of the area. Still expect light to moderate precipitation in southwest Oregon and moderate to locally heavy precipitation possible across northern California. We will monitor this period for additional headlines. .LONG TERM...Thursday through the weekend, models and ensembles support a continued active pattern. There is the potential for a strong surface low to move off the southern Oregon coast and send another moist frontal system into the area Thursday into Friday. This may bring additional strong winds to the coast and coastal waters. Snow levels are expected to be high (6000 feet or more) during this period. So most of the precipitation will fall as rain. This may allow for additional rises on rivers and streams. We will continue to monitor for flooding chances, especially for rivers and streams west of the Cascades. On the weekend, models and ensembles show more variability in the storm track but bring another low towards the region by Sunday. We will monitor this system with future model runs and update as confidence increases in the details. && .AVIATION...18/18Z TAFS...Ongoing showers are bringing a mix of low end VFR and MVFR ceilings, lowest in showers, along with widespread terrain obscurations. Freezing levels will hover around 2500 ft today. Shower activity will diminish east of the Cascades this evening, but continue along and west of the Cascades. Winds will turn southerly late this evening and overnight Monday in advance of a strong front expected late day Tuesday. Expect increasing low level wind shear concerns just beyond the current TAF period. -BPN/BR-y && .MARINE...Updated 200 PM PST Monday, November 18, 2024...Steep seas will persist through this evening as swell diminishes. Gusty west to northwest winds will continue with scattered showers and isolated thunderstorms into this afternoon. Conditions will briefly improve this evening and overnight as swell subsides, but conditions will remain hazardous to small craft. This improvement will be short-lived with conditions expected to rapidly deteriorate by Tuesday afternoon. A surface low pressure in the NE Pacific will deepen rapidly as it heads NE just outside 130W. This system will "bomb out" (a pressure drop of 24 mb or more in 24 hours) with a large portion of members indicating the pressure dropping below 950 mb as it reaches 46N and 132W by Tuesday evening. This will send a very strong cold front and associated atmospheric river toward the coast, impacting the marine waters. These solutions have been consistent over the last couple of days, leading to high confidence in dangerous conditions. There is high confidence in very strong sustained storm force winds (45-60 kt with hurricane force gusts of 65 to 70 kt) and very dangerous mountainous seas of 30 to 35 feet. The previous Storm Warning has been upgraded to a Hurricane Force Wind Warning. This strong of a storm occurs on average about once every ten years. Mariners should expect dangerous wind and sea conditions to persist through at least mid week with hazardous conditions possible through Friday. Keep checking back here for updates. BPN/BR-y && .BEACH HAZARDS...Updated 200 PM PST Monday, November 18, 2024... Seas will lower slightly tonight but a strong frontal system will move through Tuesday into Wednesday, producing very strong south winds and mountainous seas. Models support advisory conditions at a minimum, but with up to hurricane force south winds expected, this will result in warning level conditions, especially at south-facing beaches and ports. Please exercise extreme caution if you are planning to head to the beaches or even just take a trip to the coast through midweek. Be aware that conditions will be very hazardous with dangerous surf conditions much of the time and beaches should be avoided. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Winter Storm Warning until 10 PM PST this evening for ORZ025-027- 028-030. High Wind Warning from 1 PM Tuesday to 1 PM PST Wednesday for ORZ021-022-029>031. Winter Weather Advisory from 4 PM Tuesday to 4 PM PST Wednesday for ORZ029-030. High Surf Warning from 10 AM Tuesday to 4 PM PST Wednesday for ORZ021-022. Wind Advisory from 1 PM Tuesday to 7 AM PST Wednesday for ORZ023>026. CA...Winter Storm Warning until 10 PM PST this evening for CAZ080>083- 085. High Wind Warning from 1 PM Tuesday to 1 PM PST Wednesday for CAZ081-084-085. Winter Weather Advisory from 4 PM Tuesday to 4 PM PST Wednesday for CAZ085. PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST Tuesday for PZZ350-356-370-376. Hurricane Force Wind Warning from 10 AM Tuesday to 7 AM PST Wednesday for PZZ350-356-370-376. && $$ CC

259 FXUS66 KEKA 190005 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 405 PM PST Mon Nov 18 2024 .SYNOPSIS...Scattered showers continue to move onshore along the coast today. Strong winds develop Tuesday afternoon and evening as the next storm approaches. Steady, moderate rain, with embedded heavy rainfall is forecast Wednesday into next weekend. Heavy snow is possible in NE Trinity Wednesday. && .DISCUSSION...Latest IR satellite imagery depicts a large swath of cool cloud tops and convective showers over the NEPAC this afternoon. Isolated showers continue this afternoon, and isolated to scattered showers will continue tonight. Some showers and thunderstorms contained small hail today. Local observations show snow levels currently around 2500 ft, and these are and these are forecast to slowly rise to 3k to 3.5k ft through this evening. Shower activity should weaken late tonight as warm air advection in advance of the next storm begins. A significantly more potent storm system is forecast to impact the region tomorrow through this weekend. Ensemble guidance continues to hold steady on the general pattern, with all clusters depicting an atmospheric river developing offshore Tuesday and parking itself over NWRN CA Tuesday night through late in the week, possibly into the weekend. This will bring a prolonged period of moderate rainfall with an initial threat of small stream and urban flooding Wednesday and Thursday, and potentially main stem river concerns later in the week. A flood watch has been issued for most of the area in response, see the Hydrology section for more details. The initial front is forecast to bring a tight pressure gradient to the coastal counties with very strong southerly winds Tuesday evening. Sustained winds of 35 to 45 mph with gusts of 60 to 70 mph are expected on exposed ridges, coastal headlands, and portions of the coastal plain in Humboldt and Del Norte counties. A High Wind Warning has been issued for these areas, as downed trees, power outages, and difficult travel conditions are likely. The strongest winds are expected just ahead of the frontal passage, as incoming rain mixes down stronger winds present just above the surface...this is currently forecast to occur late Tuesday night. Winds then weaken but remain southerly around 10 to 20 kts behind the front on Wednesday. Meanwhile, a few deterministic models (GFS, NAM, ECMWF) continue to depict cold air getting trapped in Trinity county on Tuesday night and Wednesday morning as this system approaches, which may allow for heavy snow in the northeastern portions of Trinity county before warmer air can move in. This looks most likely east of the Alps and around Trinity Lake, as well as over Buckhorn Summit and Oregon Mtn, however may reach as far south as Highway 36. Some uncertainty remains on just how low snow levels will get. Most guidance agrees they`ll reach at least 3000 ft in NE Trinity Wednesday morning, and a small but significant portion of the guidance indicates heavy snow down to Weaverville at this time. Thus have expanded the watch to include areas above 2000 ft. Some guidance also indicates this colder air at the surface may linger through Wednesday into Thursday around Trinity Lake and in the Horn...which means heavy snow could continue for over 24 hrs on portions of Highway 3 north of Weaverville. Should this occur, one to multiple feet of snow are possible Wednesday and Thursday on portions of Highway 3 and 299. This could significantly impact travel Wednesday. Confidence is lower on snow levels for areas to the south and east, but there`s about a 50% chance over over 6 inches of snow falling on portions of Highway 36 east of Forest Glen, so have expanded the Winter Storm Watch to include these areas. A secondary surface cyclone will form along the parent trough Thursday and sweep by the coast through Thursday night. This second system looks to better align the highest moisture flux and IVT values Thursday and Thursday night, or into Friday morning. Winds and precipitation have trended stronger for this system, and it now looks like some of the highest rainfall rates may fall through that period for some locations. This portion of the forecast needs to also be watched closely since grounds will be further saturated. WPC holds a Moderate Risk for flash flooding Wednesday and Thursday, and trees and loosened branches weakened from Tuesday and Wednesday`s winds may be more prone to falling. Clusters are not resolved on the final departure of the troughs and rainfall period, which potentially lingers into the weekend. TDJ/JJW && .AVIATION...Since late morning, a few weather perturbations have been responsible for a progression of convection across the North Coast. Showers and a couple of thunderstorms (at/vicinity of the coastal locations) often impacted the Taf sites. Small hail and lightning were captured by radar, satellite and/or ground truth observations. However, Cig/Vis generally remained VFR except in a few moderate- heavy downpours. Winds became more southerly at the coast after noonday, but were mostly west to northwest over the inland valleys such as UKI. Showers will be `here and there` throughout the evening. Another approaching frontal system on Tuesday will bring more significant weather conditions to the air terminals; Cig/Vis will be more impacting with ongoing rains, and southeast-south surface winds will rev up substantially. Rain will spread across the entire region. /TA && .MARINE...Winds have a had a brief reprieve before an actual storm arrives. Winds veer southerly tonight as a storm approaches. Storm warnings have been hoisted as winds ramp up before Tuesday afternoon ahead of an approaching front. Storm force wind gusts (48 - 63kts) with isolated areas reaching Hurricane force gusts (>64kts) in the northern outer waters will make for treacherous, unruly conditions. This will spread to all area waters as Wednesday evening approaches, and so SR.W has been hoisted for all area waters through early Wednesday morning. Significant wave heights will be further elevated to 22 to 27 feet at 12 to 13 seconds early Wednesday morning in response to these winds. Northern zones will likely see the larger end of these wave heights corresponding to the strongest winds offshore, while the southern waters will experience slightly reduced 18 to 22 foot wave heights. An additional near-shore swell will maintain 12 to 14 foot seas through late week even as the most severe winds diminish. /JMM /EYS && .HYDROLOGY... && .EKA WATCHES/WARNINGS/ADVISORIES... CA... High Wind Warning from 4 PM Tuesday to 2 AM PST Wednesday for CAZ101-102. Flood Watch from late Tuesday night through late Thursday night for CAZ101>106-108>115. High Wind Warning from 7 PM Tuesday to 4 AM PST Wednesday for CAZ103-105-106. High Wind Warning from 4 PM Tuesday to 6 AM PST Wednesday for CAZ104. Winter Storm Warning from 4 PM Tuesday to 9 PM PST Wednesday for CAZ107. Winter Storm Warning from 4 PM Tuesday to 4 AM PST Wednesday for CAZ108. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PST Tuesday for PZZ450-455- 475. Storm Warning from 3 PM Tuesday to 3 AM PST Wednesday for PZZ450-455-475. Small Craft Advisory until 9 AM PST Tuesday for PZZ470. Storm Warning from 9 AM Tuesday to 3 AM PST Wednesday for PZZ470. && $$ Visit us at https://www.weather.gov/eureka Follow us on Facebook and Twitter at: https://www.facebook.com/NWSEureka https://www.twitter.com/NWSEureka For forecast zone information see the forecast zone map online: https://www.weather.gov/images/eka/zonemap.png

477 FXUS66 KMTR 190003 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 403 PM PST Mon Nov 18 2024 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 224 PM PST Mon Nov 18 2024 Clear and chilly through Tuesday with Freeze Warnings tonight for the interior North Bay and Central Coast. Strong atmospheric river begins impacting the North Bay Wednesday, with rainfall extending into the weekend. More widespread rainfall Friday into the weekend. Flooding is possible in the North Bay and northern parts of the Bay Area by the late week. && .SHORT TERM... (This evening through Tuesday) Issued at 224 PM PST Mon Nov 18 2024 Clear skies will prevail through the day with breezy northwest winds. Temperatures remain chilly with high temperatures ranging from the mid 50s to the low 60s in the lower elevations, down to the upper 40s to the mid 50s in the higher elevations. A good day to clear out gutters and storm drains! Tonight into Tuesday morning, low temperatures will drop to the mid 20s to the low 30s across the interior Central Coast, and the 30s in the interior North Bay, with Freeze Warnings in effect for both regions. A Frost Advisory is in effect for the interior East and South Bays and Santa Cruz coastal regions, where lows drop into the mid 30s. These temperatures can be hazardous for vulnerable populations, including children, the elderly, unhoused people, outdoor pets, and livestock. Tuesday should see increasing cloud cover and a shift to a south wind, while out in the northeastern Pacific, a rapidly strengthening low pressure system will gather subtropical moisture and begin directing it towards the West Coast. Foreshadowing, perhaps... && .LONG TERM... (Tuesday night through next Sunday) Issued at 224 PM PST Mon Nov 18 2024 Key messages: -Strong atmospheric river expected to stall over the North Bay Wednesday. (See "Meteorology and Timing" below) -Flood Watch is out for the North Bay Wed-Thu -4-10" of rainfall in the North Bay Wed-Sun -Locally up to 12" in the Sonoma coastal ranges -Rain moving south on Friday, much less rain (See "Impacts" below) Buckle up everyone... A strong atmospheric river will develop over the Pacific Ocean and stall out over northern California, including the North Bay, beginning on Wednesday. A rapidly developing low pressure system, to the tune of around a 60 mb deepening in 24 hours via the model guidance, in the east Pacific will pull subtropical moisture into northern California, where it will sit over the coast from Eureka to Bodega Bay into Thursday and early Friday. As an aside, the criteria for "bomb cyclogenesis" around the storm`s latitude of 42 degrees North is 18 mb in 24 hours. If the model guidance from earlier pans out, we will easily double, and possibly triple, that rate of deepening with this low. It`s an interesting fact, but it doesn`t help us communicate the most important part of the forecast: the impacts of the upcoming event, especially as it shapes up to be our first big rainmaker of the winter season. METEOROLOGY AND TIMING: Rain should start to fall in the North Bay early Wednesday morning, slowly intensifying and spreading south through the day. Intense southwest flow (above 50 knots at the 925 mb level) will stall over the coast from Eureka down to the Golden Gate. As with the previous forecast, I`ve bumped the wind gusts on Wednesday a little higher, with the end result being gusts from 40-50 mph across the North Bay coast, and higher elevations as far south as the San Mateo Peninsula and the East Bay Hills. As we go into Thursday, the initial surface low moves northwards, paralleling the coast of the Pacific Northwest and British Columbia, pulling the moisture plume a little north as well, while another surface low develops to its southwest. That cyclone also has the chance to rapidly develop as it comes into Thursday evening and Friday. Meanwhile, the intense upper level low that has been supporting these two systems will be pushed to the east by a strong downstream jet, dislodging the system from its stall, with the associated cold front dragging onto land and moving inland with it. This will bring the axis of rainfall southward through Friday into the upcoming weekend. Model guidance trends have moved the intense upper level jet a little more to the south, increasing the impacts to the northern part of the SF Bay Area. Speaking of which... IMPACTS: Impacts on Wednesday and Thursday will concentrate on the North Bay with rainfall totals ranging from 3-7" in the valleys to 6-10" across the higher elevations. Based on the intense rainfall expected with this system, a Flood Watch has been issued for the North Bay extending from Wednesday into late Thursday night, with the main impacts being flooding in urban areas and small streams. As stated earlier, now is a good time to clear out gutters and storm drains, lest the resultant rainfall find itself unable to drain off and pond onto roads and drip into buildings. The good news is that, at least in the beginning of the event, the soils are dry and will absorb the rainfall. The bad news is that the intense rainfall totals will quickly saturate them and will contribute to flooding concerns heading into the Friday and weekend. Expect further flooding products as the system evolves. Elsewhere, the initial impacts diminish quite quickly the further south you go. Rainfall totals from Wednesday and Thursday range from 1-2" in the northern East Bay and the northern and western San Mateo Peninsula, including the City of San Francisco, 0.5-1" in the Santa Cruz coastal areas and the southern East Bay, 0.25"-0.5" in the Santa Clara Valley, 0.1-0.25" in the Monterey Bay region, and virtually nothing in southern Monterey and San Benito Counties. The southern push of rain Friday into the weekend will bring more rainfall to the areas to the south of the Golden Gate. Across the South Bay, adjacent areas of the East Bay and the San Mateo Peninsula, and the Central Coast, the push from Friday into the weekend will bring more rain than the initial system on Wednesday and Thursday. For Friday and Saturday, the current forecast calls for 0.5-1.5" of rain across the Bay Area and Monterey Bay regions, with around 2-4" of rain in the Santa Cruz Mountains and the Santa Lucias. Although rainfall totals in the North Bay valleys in the same period only reach 1.5-3", as earlier mentioned, the intense rainfall on the previous two days could lead to more widespread flooding impacts, as soils have saturated and creeks and streams are filled compared to what they are now before the rainfall. Be sure to pay close attention and stay up to date with the weather forecast over the next few days for the latest updates and most accurate information. && .AVIATION... (00Z TAFS) Issued at 402 PM PST Mon Nov 18 2024 VFR conditions continue through the TAF period. Gusty northwest winds have returned across the Bay Area and Central Coast with gusts up to 27 knots expected. Winds are expected to ease overnight and become more northerly to slightly northeasterly. High clouds are expected to persist through the period and gradually start to lower ahead of rain showers late Tuesday. While showers become more likely after the end of this TAF period, winds will shift southerly and gusts will start to increase around 00Z Wednesday. Vicinity of SFO...VFR through the TAF period. Gusty NW winds continue through the evening with a 30 to 40% chance of winds gusting above 30 knots. Winds are expected to weaken overnight but will strengthen again by Tuesday afternoon/evening. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. High clouds linger with lower CIGs expected to develop after the end of this TAF period as our next system approaches. Gusty NW winds continue through the evening before weakening overnight. Winds will start to pick up Tuesday afternoon but stronger winds are expected to develop after this TAF period. && .MARINE... (Tonight through next Sunday) Issued at 402 PM PST Mon Nov 18 2024 Hazardous marine period ahead. Northwesterly breezes will diminish and seas will abate through Monday. By Tuesday, strong southerly breezes with gale-force gusts will develop ahead of the bomb cyclone with waves building to become very rough again in its wake. Expect heavy rain and thunderstorms as well. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Flood Watch from late Tuesday night through late Thursday night for CAZ502>506. Freeze Warning from midnight tonight to 8 AM PST Tuesday for CAZ504-506-516>518-528. Frost Advisory from midnight tonight to 8 AM PST Tuesday for CAZ510-513>515-529. PZ...Small Craft Advisory until 9 PM PST this evening for Mry Bay- Pigeon Pt to Pt Pinos 0-10 nm-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm. Small Craft Advisory until 3 AM PST Wednesday for Pt Arena to Pt Reyes 0-10 nm. Small Craft Advisory until 3 PM PST Tuesday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. Gale Warning from 3 PM Tuesday to 3 AM PST Wednesday for Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...Kennedy MARINE...Sarment Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea

346 FXUS66 KOTX 182340 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 340 PM PST Mon Nov 18 2024 .SYNOPSIS... Precipitation will be more showery through early Tuesday. Weather will remain unsettled through the week with the next winter storm Tuesday night into Wednesday bringing another round of widespread snow. This will result in moderate to major impacts across central Washington and minor impacts for eastern Washington and north Idaho. Additional systems passing through Thursday through next weekend will bring additional periods of lowland rain and mountain snow. && .DISCUSSION... Tonight and Tuesday: The Inland NW is in a conditionally unstable air mass through Tuesday morning with 500mb temperatures down to 35C leading to steep mid level lapse rates. This will result in continued shower activity over the region, with the highest coverage along the Cascade crest, and Idaho Panhandle with the assistance of low level upslope flow. Although snow levels will be falling overnight down to the valley floors so any showers overnight into Tuesday morning will have the potential to produce slick roads. Tuesday afternoon a brief short wave ridge moves over the region ahead of a strong weather system. JW ...HEAVY SNOW TO IMPACT CENTRAL WA TUESDAY NIGHT INTO WEDNESDAY... Tuesday night through Wednesday: Models continue to remain in good agreement in a low pressure undergoing explosive cyclogenesis as it nears the Washington coast on Tuesday and amplifies an upper level ridge over the interior western US. Deep southwest flow aloft will allow an atmospheric river to take aim at northern California and southwestern Oregon Tuesday night. As this low begins to occlude Tuesday night and gradually shifts northwestward, it will draw warm, moist air into eastern Washington and north Idaho, resulting in widespread moderate to heavy precipitation. The surface looks to start off quite dry and cold Tuesday evening with dew points in the low to mid 20s which will lead to some cooling as the column saturates from the top down. The focus for an anomalous snow event will for the Cascades, the east slopes, the Waterville Plateau, Okanogan valley and highlands as a strong east to southeast pressure gradient of -14 to 18 mb from SEA-GEG will provide favorable upslope flow into these areas. This is consistent with the ECMWF Extreme Forecast Index which highlights these areas for an anomalous snow event Tuesday night into Wednesday morning. Precipitation will fall as snow across the upper Columbia Basin, northeast Washington, Palouse, Spokane area, and the Idaho Panhandle later Tuesday evening through early Wednesday morning. While this will provide the most snow some of these lowland areas have seen so far this year, it is not being highlighted as particularly abnormal. Snow Amounts: Snow will increase over the Cascades and central Washington Tuesday evening. Strong upslope and isentropic ascent into the east slopes suggest periods of moderate to heavy snowfall rates for these areas between 10 PM and 4 AM. Snowfall will spread northeast into far eastern Washington and the Idaho Panhandle late Tuesday night. At this time, our forecast is calling for 6 to 10 inches of snow for the central Washington valleys and 10 to 15 inches for Stevens, Washington, Sherman, and Blewett Passes. There still remains uncertainty in the exact amounts for the Wenatchee area as the winds shift to the south Wednesday morning. Most deterministic models want have 850mb winds shifting to the south-southeast after 10AM Wednesday with downsloping winds off Mission Ridge ending the precipitation, however the GFS wants to hold on to the southeast flow into central WA longer. Further east into the Spokane and Coeur dAlene areas, amounts look to be much less compared to central Washington, but models are suggesting a 3 to 5 hour period of moderate snow rates early Wednesday morning before switching over to rain. There are some timing differences in the high resolution models that are available when this band will move through with the HRRR having the band over the Spokane area around 1AM and transitioning to rain by 4AM. On the other hand, the NAMNest delays the snow over the Spokane area until 4-5AM. With that said, the delayed start time would result in a slick drive Wednesday morning. Warm air nosing north/northeastward Wednesday morning will bring a transition from snow to rain starting in southeastern Washington and working its way east and north with time. Winter Weather Advisories have been issued for the lowland areas where 2 to 4 inches of snow are expected generally along areas north of I-90 from the Basin through the Coeur d`Alene area. Further north across the northeast valleys and northern Panhandle valleys look to pick up between 3 and 6 inches. Areas south of I-90 will generally be less as the warm air results in a quicker transition to rain. Around Moses Lake, snow amounts will be trickier with areas such as Quincy and Soap Lake will hold on to colder air longer with 2 to 4 inches of snow forecasted but areas further south will see less than 1 inch. Winds: The strong east to southeast pressure gradient draped across the Pacific Northwest will result in gusty winds for the Cascades, the upper Columbia Basin, the Palouse, L-C Valley, and the Blues. Ridges in the Cascades have a 50 to 70 percent chance of wind gusts above 45 mph Tuesday night and early Wednesday. Particularly over the Cascades, a Blizzard Warning has been issued for the Stevens Pass area where strong winds and snow will result in significant visibility reductions along US 2. /vmt Thursday Night through Monday: A large closed low continues to spin off the WA/OR coast Thursday Night before moving northeast to just off Vancouver Island Friday into Saturday. The continued southwest flow will send additional rounds of precipitation into the region. The Thursday Night/Friday time frame has the potential to be especially wet with precipitable water values increasing to 200-250% of normal. Ensemble means are currently projecting around 0.40-1.00" of precipitation, mostly in the form of valley rain and mountain snow. The NBM is projecting snow levels of 3500-4500 feet along the East Slopes of the Cascades and up near the Canadian border while at 6000-7000 feet over SE Washington into the Central Panhandle Mountains. The increased snow levels, rain, and low to mid elevation snow melt will contribute to increased water into area rivers and streams. No flooding is forecast at this time but this will continue to be monitored. Over the weekend into early next week the trough finally begins to move inland. As it does so precipitation chances continue, with snow levels Sunday into Monday falling as low as 1500-2500 feet. JW && .AVIATION... 00Z TAFS: A conditionally unstable air mass will continue into Tuesday morning resulting in showers mainly over the Cascades, and eastern third of WA/N Idaho with the assistance of upslope flow. Most of these showers are scattered in nature with a PROB30 group utilized. Tonight as boundary layer winds shift to south- southeast a resurgence of stratus is expected over the northern valleys including KGEG/KSFF/KCOE with a mix of IFR/MVFR CIGS. As south-southeast boundary layer winds intensity further with a deep approaching system Tuesday afternoon that should help clear the stratus out of the Spokane/Coeur d`Alene areas. A band of snow will track across the region Tuesday Night into Wednesday morning with widespread lowland accumulations expected (except Lewiston). JW FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: HREF indicates around a 70% chance of CIGS dropping back down to IFR/MVFR for KGEG/KSFF overnight into Tuesday morning, with a 40% chance for KMWH starting near 15z Tue. JW ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports, please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .PRELIMINARY POINT TEMPS/POPS... Spokane 26 37 29 40 31 41 / 20 20 60 90 60 40 Coeur d`Alene 26 37 26 39 31 42 / 50 30 30 80 80 40 Pullman 24 38 29 40 33 42 / 40 30 70 80 60 60 Lewiston 30 43 32 48 38 48 / 20 10 60 60 30 50 Colville 18 34 24 35 25 39 / 20 30 30 90 70 40 Sandpoint 24 34 22 35 29 39 / 60 50 20 100 90 50 Kellogg 26 35 23 39 34 41 / 70 40 20 90 90 70 Moses Lake 25 40 33 46 33 44 / 10 20 90 70 40 50 Wenatchee 28 36 30 39 33 40 / 10 30 100 60 20 40 Omak 24 35 29 38 31 42 / 10 20 80 90 40 30 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory from midnight Tuesday night to 10 PM PST Wednesday for Northern Panhandle. Winter Weather Advisory from 10 PM Tuesday to 10 AM PST Wednesday for Coeur d`Alene Area-Idaho Palouse. Winter Weather Advisory until 6 PM PST this evening for Central Panhandle Mountains. WA...Winter Weather Advisory from midnight Tuesday night to 10 PM PST Wednesday for Northeast Mountains. Winter Weather Advisory from 10 PM Tuesday to 10 AM PST Wednesday for Spokane Area-Upper Columbia Basin-Washington Palouse. Winter Storm Warning from 10 PM Tuesday to 4 PM PST Wednesday for Okanogan Highlands-Okanogan Valley. Winter Storm Warning from 4 PM Tuesday to 10 AM PST Wednesday for Central Chelan County-Waterville Plateau-Wenatchee Area. Winter Storm Warning until 4 PM PST this afternoon for Western Chelan County. Blizzard Warning from 4 PM Tuesday to 10 AM PST Wednesday for Western Chelan County. Winter Storm Warning from 4 PM Tuesday to 4 PM PST Wednesday for Western Okanogan County. && $$

669 FXUS66 KPDT 182342 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 341 PM PST Mon Nov 18 2024 .Updated Aviation Discussion. .SHORT TERM...Tonight through Wednesday...Lingering showers and snow showers are noted across the mountains this evening as we wrap up on the back side of a trough exiting the region, but zonal flow through Tuesday morning will continue to promote moisture moving into the Cascades with periods of light snowfall possible along and just past the crests. The real story now for the short term comes in the form of a very strong offshore low that will descend from the Gulf of Alaska and deepen considerably near the offshore borders of Canada and the US. Major models are all indicating this system will near or drop just below 940mb, bringing hurricane force offshore winds and a steady stream of southerly flow to our inland region. Although frictional effects will help to alleviate some of the strength of these winds, CAMs and ensemble solutions all agree we`re looking at a noteworthy wind event for our area, with widespread gusts of 45-60+ mph possible during the overnight Tuesday into Wednesday morning timeframe. The mountains in particular will be impacted by these winds, and combined with falling or already laid ground snow will present a significant reduction of visibilities. The ECMWF ensembles all show a widespread agreement on wind gusts of 55-60 mph during that timeframe for Snoqualmie Pass for example, and this alongside short term model agreement has led to a blizzard warning being issued for the Washington Cascades. Meanwhile, the east slopes of the Washington Cascades and the Oregon Cascades will see noteworthy snowfall alongside very gusty winds, but blizzard level conditions of limited visibilities should be much more limited for these locations, but still expect significant hindrances to travel for these areas. On the note of precipitation, the initial heaviest wave of rain and mountain snow will arrive with that stronger push of winds overnight Tuesday into Wednesday. By the time we reach the end of Wednesday, almost every location across the CWA is expected to have received 0.1+ inch of new rainfall outside of the Columbia Basin and portions of Central Oregon, with the NBM giving a high probability to this occurring at 50-100% chance. Otherwise, southwesterly flow aloft will begin to overspread warmer air and increase our temperatures, allowing snow levels to rise and limit future snowfall to the crests and peaks as we move into the end of the week. Goatley/87 .LONG TERM...Thursday through Monday... Key Messages: 1. Widespread rain chances through period. 2. Above normal temperatures extend into weekend. 3. Localized flooding possible. The extended period is characterized by a strong, upper level low pressure system that stalls off the Washington/Oregon coasts before moving onshore and through the Pacific Northwest late in the weekend. Southwest flow aloft will be dominant under this synoptic pattern, leading to widespread rain chances each day as a weak atmospheric river sets up through the workweek. The ECMWF EFI indicates Friday`s rainfall as being above the climatological normal and the wettest day in the forecast, but rain amounts on Thursday will be rather similar. Rain amounts of 0.25-0.45" are expected across lower elevations of the Basin, Central Oregon, and the Blue Mountain foothills with 0.35-0.85" of rainfall expected at higher elevations of the Cascade east slopes, John Day Highlands, and the Blue Mountains both Thursday and Friday. Confidence in these rain amounts is moderate to high (60-80%) as the NBM suggests a 25-55% chance of 0.25" of rain or more over lower elevations of the Basin and a 50-75% chance along the Blue Mountain foothills Thursday and Friday. The upper level low opens and broadens out on Saturday ahead of moving onshore mid-to late Sunday. This weakened and less organized system will still bring widespread rain showers across the area. Rain amounts of 0.50-0.75" at elevation over the Cascade and Blue Mountains, 0.20-0.40" along the Blue Mountain foothills, and 0.01-0.10" across lower elevations of the Basin and Central Oregon are expected on Saturday. Conditions will continue to dry out into Sunday, with lower elevations of the Basin staying dry as rain amounts stay confined to our foothills and mountain zones. Snow levels will hover between 5000-6000 feet Thursday and Friday, dropping to 3500-4500 feet Saturday and 2500-3500 feet Sunday. These values will keep snowfall over our mountainous terrain of the Cascades, Blue Mountains, John Day/Ochoco Highlands, and the Simcoe Highlands through the period. 1-5 inches of snowfall is anticipated to occur across the Cascade passes Thursday and Saturday. Southwest flow aloft will help to bring in a warmer and wetter airmass through the week. This will keep high temperatures in the upper 40s to low 50s through the period, which will be 2-5 degrees above normal for this time of year. Overnight lows will also be rather mild through the workweek, with morning temperatures dropping into the upper 30s to low 40s Thursday and Friday. A cooling trend develops over the weekend as the system offshore opens, weakens, and begins to push onshore. Monday morning temperatures will drop to near or below freezing over the Basin, with values dropping into the mid to upper 20s across Central Oregon. Confidence in experiencing freezing morning temperatures on Monday is moderate (50-70%) as the NBM suggests a 40-70% across lower elevations of the Basin and a 75- 95% chance over Central Oregon. There are significant rain amounts in the long-term forecast, which may lead to isolated or localized areas of flooding - primarily in and around urban and low-lying areas. Snowpack is not yet established, so the probability of rain-on-snow events is low as snow levels begin to decrease Saturday. However, there may be times when cells train and persistent moderate to heavy rainfall may lead to ponding on roadways and localized flooding near bodies of water. 75 && .AVIATION...00Z TAFS...VFR conditions currently at all sites, which will stay the course through the period. The only exception will be KDLS, which will degrade to IFR late tonight into the early morning hours on Tuesday due to reduced visibilities of 2 SM with light snow. All other sites will experience reduced ceilings of OVC050-070 during the overnight period as winds stay below 10kts for most sites. The only exception will be KALW as gusts of 20-25 kts will be possible this evening into the overnight. 75 && .PRELIMINARY POINT TEMPS/POPS... PDT 27 47 36 52 / 20 20 90 70 ALW 30 47 37 52 / 30 30 90 80 PSC 33 49 41 55 / 30 20 90 50 YKM 23 43 29 46 / 30 60 100 60 HRI 31 51 40 55 / 40 20 90 50 ELN 23 40 29 44 / 30 60 100 70 RDM 24 43 35 49 / 50 20 90 60 LGD 21 37 31 42 / 20 40 90 90 GCD 20 40 32 44 / 50 50 100 90 DLS 32 46 39 52 / 60 80 100 80 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory from 4 PM Tuesday to 10 AM PST Wednesday for ORZ044-049-505. High Wind Warning from 4 PM Tuesday to 10 AM PST Wednesday for ORZ507-508-510-511. Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday for ORZ509. WA...Winter Weather Advisory from 4 PM Tuesday to 10 AM PST Wednesday for WAZ026. Blizzard Warning from 4 PM Tuesday to 10 AM PST Wednesday for WAZ522. Winter Storm Warning from 4 PM Tuesday to 10 AM PST Wednesday for WAZ523. && $$ SHORT TERM...87 LONG TERM....75 AVIATION...75

876 FXUS65 KREV 182220 AFDREV Area Forecast Discussion National Weather Service Reno NV 220 PM PST Mon Nov 18 2024 .SYNOPSIS... * Isolated showers and cooler temperatures are expected through Tuesday. Tuesday morning lows will be in the teens and low 20s. * By Wednesday, shower chances return to Tahoe, northeast CA, and far northwest NV. Plus gusty southwest to south winds are expected across the whole area. * A potentially more significant storm arrives late Friday into Saturday bringing strong winds, and chances for rain and snow. && .DISCUSSION... We had gusty winds along with some valley rain and mountain snow last night. Currently, we have mostly fair conditions across the region, but with some typical breezes this afternoon. There is a very low chance for light showers near the CA/OR border, NE CA and the Sierra. Otherwise, we should be dry. Chilly conditions persist through tomorrow. Widespread areas will observe hard freezes again tomorrow morning. The good news is that temperatures will be slowly rising through late this week. The weather pattern changes on Wednesday with the approach of an upper level storm system that will hover off the Pacific NW. This position will allow for a deep plume of moisture, aka atmospheric river (AR), to be advected towards northern CA for the second half of the week. The arrival of this system brings snow accumulations for far western Lassen and central Plumas county above 5000 ft. The last couple of model runs have increased the precipitation amounts resulting in higher probabilities of snow in the aforementioned area. Therefore, there is about a 60-90% chance of exceeding 4 inches of snow. For the Tahoe basin and near the Donner Pass, the probabilities are 40-70% in elevations above 7000 ft with the best chances near the Sierra crest and over the west slopes. Snow chances diminish the farther south we go. This leads to the Eastern Sierra only having a 10-40% chance of exceeding 4 inches. The AR brings a warmer air mass, so snow levels will rise by early Thursday to about 7-8 kft. This will hinder the snow accumulations, and melt some of the snow which will lead to ponding of water in low-lying areas and rises in creeks and rivers over northeast CA. The secondary hazard that we are expecting on Wednesday is gusty southwest to south winds. The upper level jet will set in northern CA and southern OR leading to an increase in the pressure gradient near the surface. Therefore, expect gusts of 30-40 mph in the valleys across the region again with gusts exceeding 70 mph in the Sierra crest. NBM is also showing a 30-50% chance of seeing 50+ mph gusts, while ECMWF Extreme Forecast Index (EFI) is also indicating an anomalous event. Talking about the EFI, it looks like we have another wind event this Saturday after a break on Thursday and Friday with slightly weaker winds. Pretty much this is when the upper trough that was hovering off the Pac NW finally moves inland. Again expect gusty winds with this system during the afternoon hours. But of more concern is the amounts of precipitation associated with it as the last of this AR finally passes through. The periods of rain and snow will lead to a 20-50% chance of getting an inch of liquid in the Sierra Front and 40-80% for the Sierra and NE CA between Friday and Sunday. -Crespo && .AVIATION... Wind gusts die down through the evening for all TAF sites, and remain light and variable through the period. VFR conditions expected for all sites except for KTRK, where some FZFG is possible tonight until 19/17Z as temperatures drop to the teens. In addition, periods of increased turbulence is expected along the Sierra until 19/05Z. Beyond that, we have two systems this week that could bring snow to mountain terminals and rain to valley terminals. The first system aims to bring a rain/snow mix to KTRK/KTVL Wednesday through Thursday. The second system (Friday through Saturday) looks to bring snow to KMMH/KTVL/KTRK and rain to KRNO/KCXP/KMEV. For more details, see the discussion above. -Giralte && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

240 FXUS66 KSTO 182221 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 221 PM PST Mon Nov 18 2024 .SYNOPSIS... With a brief lull in activity today, temperatures trend cold overnight into Tuesday morning, with widespread, low elevation frost possible. Precipitation chances then rapidly return to the region by midday Tuesday, with periods of moderate to heavy precipitation then expected through the end of the week and into the weekend. *Freeze Warning: 10 PM tonight through 10 AM Tuesday morning for elevations below 2000 feet. *Cold Weather Advisory: 10 PM tonight through 10 AM Tuesday morning for elevations above 6000 feet along the Sierra. *Winter Storm Warning: 4 PM Tuesday through 10 PM Wednesday for elevations above 3500 feet along the Sierra/ southern Cascades, Coastal Range, and Shasta County mountains. *Flood Watch: 10 PM Tuesday through 4 AM Saturday for Valley/foothills locations generally north Interstate 80 and below 3000 feet. .DISCUSSION... As of early this afternoon, mostly to partly sunny skies are evident across interior NorCal via latest GOES-West satellite imagery as transient ridging aloft between systems builds in. Despite more plentiful sunshine today, breezy north winds will keep temperatures slightly below normal today, with mid 50s to low 60s across the Delta, Valley, and foothills, and 30s to 40s at higher elevations. As winds lessen this evening and skies remain mostly clear overnight, low temperatures by Tuesday morning look to drop to the low to mid 30s across the Delta, Valley, and foothills, with temperatures 5 to 25 degrees at higher elevations. As a result, cold weather impacts are expected at high elevations, with widespread, low elevation frost anticipated as well. Ensemble guidance continues to show increasing confidence in the evolution of a trough digging southward from the Gulf of Alaska mid to late week. Current consensus has the trough approaching the Pacific Northwest coast on Tuesday, with attendant precipitation impacts beginning across northern portions of the forecast area by Tuesday afternoon/evening. As this trough is expected to rapidly deepen as it nears the coast, heaviest precipitation and strongest winds with this initial wave are expected overnight Tuesday into Wednesday, although additional periods of moderate to heavy precipitation are expected to persist through the end of the week as well. As broad ridging amplifies across the Intermountain West through the middle of the week, the Pacific Northwest trough is expected to stall and briefly retrograde westward into Thursday. While precipitation still looks to persist as this occurs, a brief period of comparatively lighter precipitation may be possible midday Thursday into Friday morning. As the precipitation looks to arrive in a few different waves, the initial wave is expected with the trough remaining offshore, providing a favorable fetch for moisture advection into NorCal along with ample forcing. Current precipitation forecasts from midday Tuesday through Friday morning indicate rainfall of 3 to 6 inches possible across the Valley and foothills north of Interstate 80, with some potential for precipitation accumulations up to 8 inches within the foothills as well. From Interstate 80 southward, precipitation accumulations drop off to 0.5 to 2 inches possible, with highest totals expected closer to Interstate 80. Additionally, south-southeast winds are expected to become gusty on Wednesday. Generally gusts 25 to 35 mph are anticipated throughout the Valley/foothills, with gusts up to 50 mph possible along the Sierra. Snow levels are expected to vary through this first wave of precipitation, with cold temperatures initially on Tuesday gradually nearing seasonal normals moving through the remainder of the week. As a result, snow levels 3000 to 4000 feet are anticipated Tuesday into Wednesday morning, rising to 4500 to 5500 feet by Wednesday afternoon, further settling around 6000 to 7000 feet by Thursday. With the heaviest precipitation expected overnight Tuesday into Wednesday when snow levels remain lowest, impactful snowfall of 4 to 8 inches will be possible down to 3500 feet through Wednesday night for the Coastal Range, Shasta County mountains, and northern Sierra/southern Cascades. Additionally, snowfall accumulations of 8 to 18 inches are anticipated for these locations above 4500 feet, with up to 2 feet possible over peaks. Additional snowfall accumulations will be possible above 5500 feet along the remainder of the Sierra, including Interstate 80 and Highway 50, with totals 3 to 6 inches possible. .EXTENDED DISCUSSION (Friday THROUGH Monday)... Moving toward the end of the week and into next weekend, precipitation chances are expected to persist across interior NorCal. This will be the product of the aforementioned offshore trough beginning to slide inland over the weekend. Despite the onshore shift, ensemble guidance indicates that the trough will only gradually progress eastward with time, prolonging the window for additional precipitation impacts through the weekend and potentially into early next as well. As this system becomes more centered over NorCal, snow levels look to fall to around 4000 to 5000 feet again throughout the weekend. While exact details regarding precipitation totals from Friday into early next week remain somewhat uncertain, current probabilities of precipitation exceeding 2 inches linger around 40% to 70% for the Delta, central/southern Sacramento Valley, and northern San Joaquin Valley, jumping to 70% to 90% probabilities across the northern Sacramento Valley and surrounding terrain, as well as along the Sierra. Given lowering snow levels through the weekend, additional mountain travel impacts will be possible along the Sierra, with current probabilities of exceeding 1 foot of snow around 60% to 80% along the Sierra above 5000` through Monday. With the active weather in the forecast this week, be sure to stay up to date with the latest forecast at weather.gov/sto and check current road conditions at quickmap.dot.ca.gov before traveling! && .AVIATION... Primarily VFR conditions across Interior Northern California through at least 18z. Around 20z Tuesday, MVFR conditions possible due to showers in the Valley. Delta and northern San Joaquin Valley locations could have breezy winds with sustained speeds up to 12kts and gusts up to 15kts through 00z Tuesday. Otherwise, surface winds generally at or below 12 kts. && .STO WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 10 PM this evening to 10 AM PST Tuesday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode- Mountains Southwestern Shasta County to Western Colusa County- Northeast Foothills/Sacramento Valley-Northern Sacramento Valley- Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta County-Southern Sacramento Valley. Winter Storm Warning from 4 PM Tuesday to 10 PM PST Wednesday for Mountains Southwestern Shasta County to Western Colusa County-Shasta Lake Area / Northern Shasta County-West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. Flood Watch from Tuesday evening through late Friday night for Central Sacramento Valley-Mountains Southwestern Shasta County to Western Colusa County-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley-Shasta Lake Area / Northern Shasta County. && $$

716 FXUS65 KMSO 181919 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1219 PM MST Mon Nov 18 2024 .DISCUSSION... KEY MESSAGES: - Active weather with low to moderate impacts will continue through this week causing nearly continuous snow in the mountains. - An atmospheric river will bring a lot of moisture to the mountains of central Idaho and northwest Montana Wednesday through Friday. - Colder air will be over northwest Montana this weekend with a 40% chance of 1 inches or more of snow in Kalispell, and an 80% chance of 8 inches or more along the Continental Divide. A cool, unstable air mass is in place over the region today. Most of the moisture is concentrated in the lower levels of the atmosphere, so there isn`t much to work with, but there is enough for some snow showers. The average wind speeds below 10,000 ft will support some organization and banding late this afternoon, but as the flow weakens this evening any showers are expected to lose their organization and be very sporadic. Snow showers this evening will mainly be a nuisance, but travelers should be prepared for changing conditions while traveling this evening. Tomorrow, Tuesday, will be the clearest, most settled day of the week, but there will still be snow showers coming into the mountains of northwest Montana and central Idaho. These will be light showers with only minor accumulations. Wednesday marks the arrival of the next atmospheric river. While this atmospheric river won`t be too intense, it will be long lasting through Friday. For the 3 day period, low end forecasts (10th percentile) have 0.75-1.5 inches of moisture in the central Idaho mountains and 1-2 inches along the Montana-Idaho border in the Idaho panhandle region. Glacier park is looking at 0.5-1 inches on the low end. The high end forecasts (90th percentile) have 2-3 inches in central Idaho and along the Montana-Idaho border. In the Bear Mountain area northeast of Lake Pend Oreille, the NBM is showing a 10% chance of 5 inches of rain in 3 days. Glacier National Park has 2-3 inches of rain for the high end forecast. In the springtime, this amount of rain would be a concern for flooding, but several factors this time of year will help to mitigate that. First, the high rain amounts occur over a 3-day period, so much or the moisture will have time to run-off. And while snow levels will rise during the event, the highest elevations will remain snow throughout the event. And finally, area rivers and streams currently have a lot of capacity, so it would take a tremendous event to cause any flooding. Finally as the atmospheric river leaves the area Saturday, the jet stream sets up south of the area and we remain in a cool, unstable air mass. Northwest Montana will be the most likely to receive any valley level snow with a 40% chance of an inch or more of snow over the weekend in Kalispell. Chances are currently half that in Missoula and Butte. However, the mountains all across the northern Rockies region will benefit from some snow next weekend. In yesterday`s discussion we mentioned the possibility of some arctic air spilling over the Continental Divide Friday or this weekend. Ensembles have backed off on that considerably and the overall pattern with strong westerly flow is no longer supportive for an event like that. Ensembles are focusing in on a "glancing blow" pattern where the cold air stays east of the Continental Divide. However, there is plenty of cold air up north, and some ensembles continue to try to bring some of it down west of the divide by mid-next week. We`ll keep watching this pattern closely for any potential high impact winter weather. && .AVIATION...Moist westerly flow in the base of a broad trough over the region will cause continuing cloud cover and mountain obscurations through the night. Unstable conditions will allow some convection to develop this afternoon and evening, but overall rising heights and vertically aligned westerly winds around 20 knots should keep most of the convection attached to the mountains with occasional light showers spreading across the valleys. Any impacts from showers will generally impact terminals for less than an hour, and otherwise VFR to MVFR conditions are expected. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...ID...&& $$

935 FXUS65 KBOI 182107 AFDBOI Area Forecast Discussion National Weather Service Boise ID 207 PM MST Mon Nov 18 2024 .SHORT TERM...Tonight through Wednesday night...Zonal flow tonight will give way to a brief ridge aloft Tuesday, and by Tuesday night a long fetch of SW flow will become established across the PacNW. This flow will bring in an atmospheric river. Showers will continue tonight into Tuesday, but the substantial precipitation moves in Tuesday night and will continue into the long term period. The chance of precipitation reaches its maximum (for the short term) Wed night with a 50-90% chance (going roughly from south to north). Snow levels will initially be on valley floors, and will remain there through Wednesday morning, but will rapidly rise Wed afternoon and night. By late Wed night, snow levels will range from around 4000 ft AGL in Baker County up to around 7000 ft AGL in southern Harney and Malheur counties. The Idaho mountains will be up to around 5000 ft at that time. Winds will increase Tue night into Wed, with gusts 40-50 mph on the higher terrain in SE Oregon, and 30-40 mph in much of the area. This is due in part to a strong surface low off the coast (which is associated with the remnants of a typhoon that was off the coast of Asia just 5 days ago!). Through the entire short term, snow totals in the mountains will range from 1-3 inches in places like Idaho City, Halfway, and Garden Valley, with 5-9 inches in McCall, Sumpter, and Donnelly. Up to two feet will fall in the highest elevations, including in the highest terrain of Baker County to the north of Halfway. The combination of wind and snow will lead to snow blowing nearly horizontally at times, but snow accumulation on roads should be minimal. .LONG TERM...Thursday through Monday...SW flow aloft will continue the long term period. Snowfall will continue at higher elevations, with rain below around 7000 ft AGL from Thu evening through early Sat morning. After that time, snow levels will fall again, changing rain back over to snow in (for ex) McCall. Light snow is expected above around 3000 ft AGL Saturday night through Monday. Winds will increase again as a system moves through Friday night and Saturday, with gusts 20-35 mph expected in higher terrain and also over much of SE Oregon. Another weaker system may arrive Monday, and there is sufficient confidence to keep a chance of precipitation (30-70%) in the forecast. && .AVIATION...Mostly VFR, but scattered snow/rain showers through the evening, resulting in MVFR to LIFR at times. Surface winds: SW-NW 10-20 kt with gusts to 20-30 kt this afternoon. Winds aloft at 10kft MSL: westerly 20-30 kt. KBOI...Mostly VFR but with scattered snow showers through 19/02Z. MVFR/IFR possible in snow, with best chance of light accumulation during the evening. Surface winds: W-NW 5-15 kt, with afternoon gusts up 20 kt, becoming variable around 5 kt around 19/02Z. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...SP LONG TERM....SP AVIATION.....SP

856 FXUS65 KLKN 182205 AFDLKN Area Forecast Discussion National Weather Service Elko NV 205 PM PST Mon Nov 18 2024 .SYNOPSIS...Look for isolated snow showers this evening with some partial clearing late. Low temperatures across northern and central Nevada tonight will be chilly with readings some eleven to thirteen degrees below normal for this time of year. After another cold afternoon Tuesday, a warming trend is expected Wednesday through Friday. The potential for more active weather increases for the upcoming weekend. && .SHORT TERM...Tonight through Tuesday night. Low scattered to broken clouds remain in the wake of the upper trough passage today. Temperatures are well below normal with brisk west to northwest winds common over northern and central Nevada. Some light snow showers are noted on radar, mainly isolated in nature and not dropping much in the way of accumulation. Weak lift from an upper jet and isentropic lift at 290K will combine with scant moisture to allow for isolated, light snow showers to develop during the overnight but will not produce anything in accumulation. Though skies are not expected to clear entirely, any partial clearing will allow the temperatures in the area to drop like a rock. Readings will be in the single digits and teens. Here are probabilities of minimum temperatures of 10 degrees or lower for select locations in northern and central Nevada for tomorrow morning, the 19th of November: Austin - 30% Battle Mountain - 5% Elko - 55% Ely - 90% Eureka - 70% Ruth - 60% Spring Creek - 60% Tonopah - 0% Wells - 40% West Wendover - 0% By Tuesday and Tuesday night, transitory upper ridging will move across the area. Many areas will see a mix of clouds and sun through the day along with relatively light winds. Afternoon highs will not recover much with readings in the mid 30s to low 40s. Here are probabilities of maximum temperatures of 40 degrees or lower for select locations in northern and central Nevada on for the afternoon hours on Tuesday. Austin - 100% Battle Mountain - 45% Elko - 95% Ely - 75% Eureka - 100% Ruth - 100% Spring Creek - 100% Tonopah - 60% Wells - 100% West Wendover - 90% Overnight lows will not be as cold Tuesday night with clouds hanging around and lows in the teens and 20s. .LONG TERM...Wednesday through Monday An expected multi-day atmospheric river event with ample Pacific moisture streaming into northern California From Tuesday through Friday will bring copious rainfall amounts to northern California but only light showers to portions of northwestern and far northern Nevada during this time frame. With broad and consistent southwest flow a warming trend will continue through the latter part of the work week with highs reaching into the 50s as early as Thursday and some upper 50s showing up for Friday. Cloud cover will keep lows in the 20s. A trough and attendant cold front is expected to finally push into the Great Basin region Friday night into Saturday promoting a more widespread precipitation event across the northern half of Nevada. Snow accumulation will likely still be limited to mountain areas Saturday with sufficiently cold air and low enough snow levels for some valley impacts by Saturday night. One inch of snow or more in valleys is still a low likelihood over the weekend with most valleys seeing a 20% chance or less of 1 inch or more. Long term ensemble guidance continues to suggest an active weather pattern remaining through early next week. Temperatures will be cooler early next week overall with highs in the 40s and lows in the teens and 20s. && .AVIATION...Isolated snow showers across northern Nevada will dissipate through the late afternoon and early evening hours. Brief reductions in visibility and CIGs can be expected if shower moves directly over the airport at KEKO through 04Z. Otherwise, winds will diminish this evening remaining below 10 knots or so across central and northern Nevada through Tuesday with the exception of KTPH where a brisk north wind of around 15 knots with gusts to 25 knots is expected through 04Z. VFR conditions are expected Tuesday with high cloud cover moving back into northern Nevada. && .LKN Watches/Warnings/Advisories... None. && $$ 86/93/93