701 FXUS66 KSEW 201619 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 819 AM PST Mon Jan 20 2025 .UPDATE...As advertised, cold temperatures are being felt this morning. Widespread 20s are on the thermometer as we gradually warm up. Some locations have even cooled to the upper teens such as Bremerton and Arlington. The Cold Weather Advisory has been allowed to expire but a chilly day is certain to remain. Any lingering freezing fog will fade as the day progress with sunny skies expected. The previous discussion remains below along with an updated marine/aviation section. && .SYNOPSIS...High pressure will dominate the weather into the middle of this week, bringing dry conditions and cold overnight temperatures. Lows will fall below freezing over much of Western Washington at least into mid-week while daytime highs will remain below normal. && .SHORT TERM /TODAY THROUGH WEDNESDAY/...Clear skies over much of W WA this morning via satellite imagery allowing for some very cold temperatures to emerge. Lower 20s present over some locations such as Shelton and Arlington while on the higher end of the range, mid 30s are present in Everett and at Sea-Tac. The majority of remaining obs falling somewhere in the middle. Given this wide spread of temp range, it is difficult to get a feel for how current Cold Advisory is handling the situation. Will leave inherited headline in place mainly on the grounds that some locations within the advisory area are seeing dewpoints that, if reached, would bring these sites within criteria. Model solutions remain largely unchanged, providing difficulty in creating original discussion content. The upper level ridge will begin its slow breakdown today as the ridge axis finally reaches W WA. Weak trough slides in Tuesday with only increasing clouds to come with it. Ridging rebuilds into the area for Wednesday. The aforementioned clouds will help to take the edge off of these cold overnight temperatures and providing at least a couple degrees of warming, ranging from the mid 20s to near 30 both tonight and Tuesday night. Daytime highs may see a degree or two of warming between today and Tuesday, but not enough to impact the forecast temperature range of the lower to mid 40s...with Wednesday being nearly identical to its predecessor. 18 .LONG TERM /THURSDAY THROUGH SUNDAY/...Discrepancies in the deterministic models persist when considering Thursday, again all rooted in the amplitude of the second ridge mentioned in the short term. ECMWF maintains a lower amplitude, making W WA susceptible to a weak trough quickly passing through late Thursday and early Friday. The GFS offers a higher amplitude ridge, keeps the timing similar to the ECMWF with a trough coming in late Thursday, but deepens this feature to the point where precip would persist for much of the day Friday before the system exits Friday night. As has been the case, the NBM has latched on to this uncertainty and is trying to play PoPs down the middle...making a case for some precip while still keeping things out of the likely or categorical range that the GFS solution would suggest. Taken within the scope of the ensembles, however, this solution, PoPs of around 40 pct, ends up being an outlier on the high side of things as the statistical mean remains more in the 10-20 pct range. As such, while precip cannot be ruled out, chances do seem lower than what is forecast. Ridging returns for Saturday and Sunday, and while still over the Pacific waters, its influence will be enough to bring a return to dry conditions. Daytime high temps in the extended do not seem to vary much from the short term, ranging in the lower to mid 40s for the remainder of the forecast period. Overnight lows Thursday night will benefit from the incoming system and its associated clouds, bringing W WA the first night with lows above freezing in quite some time...but not by much...ranging in the lower to mid 30s. Falling under the influence of another ridge will produce lows akin to the short term, falling once again below freezing and ranging from the mid 20s to around 30 from Friday night through the end of the forecast period. 18 && .AVIATION...An upper level ridge over Western Washington will weaken later this afternoon and tonight as a weak trough moves through tonight. The ridge will rebuild on Tuesday. Northwest flow aloft will transition more westerly tonight. Areas of LIFR cigs and vsbys with FZFG from OLM southward, and in localized areas of south Puget Sound. Conditions will slowly improve in these areas to VFR by later this morning into midday. Otherwise VFR conditions elsewhere with increasing high clouds through today. Generally light winds through tonight. KSEA...VFR conditions with increasing high clouds through today. Lighter east winds this morning will transition more to NE from 4 to 8kts by midday, then becoming light E/SE tonight. JD && .MARINE...High pressure will remain over the waters today. A weak system will move by to the north Tuesday. High pressure will build back into the waters Tuesday night and remain through Thursday. A weak system will move through the area Thursday night into Friday. Possible small craft advisory winds in the coastal waters Thursday into Friday. && .HYDROLOGY...No river flooding in the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

037 FXUS66 KPQR 202220 AFDPQR Area Forecast Discussion National Weather Service Portland OR 220 PM PST Mon Jan 20 2025 .SYNOPSIS...High pressure over the area will persist through at least Thursday, with mostly sunny days and chilly nights. Thursday night into Friday, a weak front will move over the area and increase chances for light precipitation. At this point, no winter weather concerns. && .SHORT TERM...Now through Wednesday night...Dry weather with mostly sunny skies prevail through the rest of the afternoon as high pressure remains over the region. Breezy easterly winds continue through the Columbia River Gorge and eastern Portland/Vancouver Metro Area, however, winds will gradually weaken this evening as KTTD-KDLS pressure gradients loosen. Tonight into Tuesday morning, an upper level shortwave trough will quickly brush the region, increasing mid to high level cloud cover. No precipitation is expected for our area from this shortwave, but it will return onshore flow with westerly winds through the Gorge. Expect another chilly night; since winds are forecast weaker, it doesn`t look like apparent (feels-like) temperatures will meet criteria for any cold advisory. Skies should begin to clear more by Tuesday afternoon as the upper level ridge re-builds. High pressure persists through at least Wednesday, maintaining sunny skies and chilly nights. -Alviz && .LONG TERM...Thursday through Sunday...The first pattern shift of the week arrives on Thursday afternoon. A front from the Gulf of Alaska will shift southward through the day. There are increased chances for precipitation but the highest accumulations will be observed along the mountains. Cold air will still be in place at the surface with 850 mb temperatures around -4 deg C. While precipitation will be fairly light, if a stronger band of precipitation sets up, could see colder air mix down from aloft and bring a bit of snowfall to the Columbia River Gorge. At this point, no concerns for significant winter weather on Thursday into Friday. Moving into the weekend, the majority of WPC cluster analyses show troughing moving southward into the Great Basin and southwestern US. At the same time, guidance is showing positively tilted ridging of building over the Pacific Northwest, which would continue the repeated trend of dry weather with sunny skies and chilly nights. -Alviz/Muessle && .AVIATION...High pressure over the airspace will maintain VFR conditions through most of the TAF period. Could see a return of LIFR fog overnight around 12Z Tuesday for KHIO and areas south of KMMV once winds begin to decrease this evening. Expect offshore easterly winds throughout most of the area, with light northerly winds in the central/southern Willamette Valley. This afternoon, expect strong easterly winds through the Columbia River Gorge and reaching near the metro, with gusts up to 30-35 kt in the Gorge. Around 06-12Z Tuesday, expect winds throughout the airspace to decrease below 5 kt and become southerly in the central/southern Willamette Valley. Cold overnight temps and clear skies continue, supporting frosty conditions on the ground and freezing fog possible. PDX AND APPROACHES...Clear skies and VFR conditions expected through the TAF period. Will see easterly winds 10-15 kt with gusts up 20 kts until 00Z Tuesday and decrease thereafter. Gusty east winds with gusts up to 25-30 kt at KTTD until around 06Z Tuesday. ~Hall && .MARINE...High pressure over land currently maintains offshore flow over the waters today. This high pressure will weaken tonight into tomorrow as a weak disturbance moves over the area for a period of light and variable winds. High pressure will rebuild over the NE Pacific on Wednesday, returning north winds through the rest of the week and into the weekend. There is a 50-75% chance that wind gusts of 21 kt return to the waters late Thursday through Friday but timing and strength still remains a bit uncertain. A series of NW swells will maintain 6-8 ft seas through Wednesday morning. Friday, a larger swell will bring a 60-80% chance of seas building above 10 feet for the outer coastal waters. ~Hall && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

807 FXUS66 KMFR 201756 AFDMFR Area Forecast Discussion National Weather Service Medford OR 956 AM PST Mon Jan 20 2025 .Updated Aviation Discussion. .DISCUSSION...Not much change in the overall pattern is expected through most of next week. Upper level ridging over the eastern Pacific and just offshore of the West Coast and very strong and broad troughing over almost the entire continent will keep the area generally under high pressure with north flow aloft. In the low to mid levels, dry east flow will prevail, with downslope effects keeping ridges and midslopes warm and very dry, with strong inversions trapping colder, moist air in the valleys, especially west of the Cascades. In other words, the day-to-day forecast will change very little for much of the week. With the strong inversions in place, and with no active weather to break them, stagnate air conditions and fog/low stratus clouds are expected to continue in area valleys. An Air Stagnation Advisory remains in effect. A weak shortwave will move over the ridge Tuesday, but it likely won`t be enough break things up, so it`s possible the stagnant air could last through most of next week. The dry east flow will also continue to produce a Chetco Effect, keeping temperatures in and around Brookings much warmer than the rest of the area through at least Monday afternoon. There`s some evidence pointing towards a slight disruption in the pattern towards the end of the week with a shortwave trough dropping in from the north. The operational models are in pretty good agreement with the trajectory of the upper trough, which is one that typically does not result in any precipitation for most of the area, aside from the coast and maybe the north-facing slopes. More likely it will be a dry cold front that will drop into the area Friday with gusty north to northeast breezes east of the Cascades and mid slopes and ridges along the Cascades and coastal mountains in southwest Oregon and western Siskiyou County. Despite an overly wet NBM solution, the deterministic models and the majority of the ensemble members show very little precipitation, and have it coming in 12 or more hours after the NBM. Have trended the forecast drier, and also delayed the onset of precipitation to bring the forecast in line with the majority of forecast solutions and the known characteristics of systems like this one. Most likely, the system will pass through the area with little to show for it other than increased clouds, a hundredth or two of precipitation scattered around the area, and a temporary period of good mixing and broken inversions. This disruption will be brief, with high pressure, stagnate conditions, and strong inversions returning for latter part of next weekend into most of the following week. The model suites do suggest a pattern change could be in the works towards the end of the month with the upper ridge flattening out enough to allow systems to move into the area, and the long term ensembles trending wetter, but much remains to be seen. Stay tuned. -BPN && .AVIATION...20/18Z TAFS...Freezing fog is bringing LIFR levels to Medford. The morning sounding shows a very dry air mass approximately 1200 feet AGL. Guidance shows the fog and low clouds burning off towards 21z. Given the shallow moist layer, it`s possible Medford could break out early this afternoon and have introduced this in the TAF. However, we`ll keep a watch on the trend of the satellite image and adjustments willbe made as needed. It`s also worth noting improving conditions could be delayed by an hour or two. Satellite image shows low clouds and fog burning off in the Umpqua Basin and Roseburg could clear out towards 18z and have this as the prevailing condition in the TAF. Low clouds and fog will return in the same areas as this morning early this evening and lasting until the end of the TAF period. Elsewhere, VFR conditions will continue through the TAF period. -Petrucelli && .MARINE...Updated 200 AM Monday, January 20, 2025...Gusty north to northeast winds under a thermal trough pattern will maintain conditions hazardous to small craft for the outer waters south of Nesika Beach this morning. The thermal trough along the coast will weaken this afternoon into Tuesday night allowing conditions to fall below advisory levels and gradually improve with west-northwest swell dominated seas reaching a minimum at around 5 to 6 ft at 14 seconds. The thermal trough is expected to strengthen again Wednesday with seas likely becoming steep, at least for the outer waters south of Cape Blanco. Gusty north winds are expected to continue to increase late in the week with gales possible and steep to very steep seas likely. -DW && .BEACH HAZARDS...Updated 200 AM PST Monday, January 20, 2025... The sneaker wave risk is past its peak, but will rise with an increased risk on the incoming tide early this morning. A moderate risk will continue at southern Oregon beaches through this afternoon. Sneaker waves are a type of wave that can run higher up the beach than a normal wave. Sneaker waves can wash over pathways or rock outcroppings. They can lift and carry logs, which can then strike or pin beachgoers. Sneaker waves can knock a person off their feet and carry them out to deeper waters, where hypothermia becomes possible. Sneaker waves can pose a lethal threat. As these conditions may occur while the sun is down, visibility will be limited. Always keep your eyes on the sea and use extra caution. && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 10 AM PST Tuesday for ORZ021- 023>026-029>031. Beach Hazards Statement through this afternoon for ORZ021-022. Freeze Warning until 8 AM PST this morning for ORZ021. Freezing Fog Advisory until 9 AM PST this morning for ORZ024- 026. CA...None. PACIFIC COASTAL WATERS...Beach Hazards Statement through this afternoon for PZZ350-356. Small Craft Advisory until 10 AM PST this morning for PZZ376. && $$

096 FXUS66 KEKA 201324 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 524 AM PST Mon Jan 20 2025 .SYNOPSIS...Continued dry through Thursday, with some precipitation potential toward Friday and into next weekend. Chilly nights and mornings with areas of frost and patchy fog into mid- week. Potential for gusty winds exists for Lake County Monday. Potential for gusty winds return for much of the entire area Friday and Saturday. && .DISCUSSION... Key Messages: Gusty winds for Lake County today through this evening, with gusty winds a concern for a larger portion of the area Friday and Saturday. Frost potential (including the coast) through at least early next week. Fog potential exists for low-lying valleys through at least Wednesday morning. Weather Pattern Overview: Upper level ridge over the eastern Pacific ejects a couple of shortwave ridges on its eastern periphery for early to mid week to ensure dry weather through Thursday. The first shortwave ridge axis arrives tonight, and the second arrives Wednesday night. A consistently forecast trough is still forecast from ensembles to slide into the eastern periphery of the eastern Pacific ridge and will have at least some influence on our weather from Friday through Sunday night, although the mean trough axis will remain southeast of the CWA. Therefore any precipitation amounts for Friday morning through Sunday night will be light. We will be on the lookout for gusty winds Friday and Saturday, focused on the coast for Friday, and farther into the interior for Saturday. Forecast Confidence and Deviations: Synoptic pattern confidence is high as ensembles continue to have good agreement and consistency with the Omega Block High dominating our weather through Thursday before the eastern periphery gives way to the trough sliding in from the eastern side with increasing magnitude. Therefore confidence is high for a dry forecast heading into Thursday. Probability of northeast wind gusts reaching more than 45 mph for Lake County are about 20% for Clearlake, but higher elevations near Middletown will be around a 50% chance of reaching wind gusts of more than 45 mph. We stand a 30-60% chance of hitting gusts greater than 45 mph along the coast. And a 60% chance of wind gusts greater than 45 mph on Saturday for Clearlake in Lake County. Any rain amounts appear to be rather light for Thursday night through Saturday. With the aforementioned trough comes a bit of precipitation potential. Chances of a total of 0.05 inches or more from Friday morning to Sunday night will be about 50% for most of Humboldt and Del Norte Counties, down to about 20% chance for Lake County and eastern Trinity County. The most likely period for most rainfall will be 10PM Friday to 4PM Saturday. Chilly temperatures will be a continues problem. Chance of temperatures 32 or lower by next Sunday morning a week from now will be 30-60% along the Humboldt and Del Norte Counties coast to near 100% for most of Trinity County. Sky cover was increased Friday afternoon and night compared to the deterministic NBM with the increased influence of the upper trough. && .AVIATION...Skies are mainly clear this morning across the area and winds are light at the airports. In Mendocino and Lake counties the higher elevations are seeing gusty winds to 30 mph which cause some low level wind shear, but it looks to be less than 20 kt so have not included it in the KUKI taf. Winds at the TAF sites are expected to remain light. A few of the river valleys are seeing stratus this morning, but coverage is limited. Clear skies are expected through the day and much of tonight as well. MKK && .MARINE...Winds have diminished close to the coast and will continue to diminish well offshore this morning. Tonight the wind turn southerly around 5 to 10 kt and this continues through Tuesday. In additions to the winds there is a 16 seconds swell at 7 feet moving through the waters. The buoys are showing some set behavior in these waves. This will create a risk for intermittent larger waves breaking in the shallow areas or shoals. Wednesday there is decent agreement in the models that the northerly winds will start to increase again, around 15 to 20 kt by the afternoon. Late Wednesday night and Thursday these winds diminish some, although exactly how much is uncertain. Another long period wave is expected to move through on Thursday, although the current models only show it around 3 to 6 feet Thursday night. A more significant wind event is Friday and Saturday. The global ensemble mean is show a 40 to 60 percent probability of sustained gale force winds. If this trend continues the forecast will likely need to be increased. MKK && .BEACH HAZARDS...The long period swell is currently around 8 feet at 16 seconds bringing breakers of around 15 feet. The buoys are continuing to indicate some set behavior, although it is less pronounced than yesterday on the buoys. This is likely still creating some sneaker waves. The beach hazard statement looks to be on track. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement until 4 PM PST this afternoon for CAZ101-103-104-109. Wind Advisory until 10 PM PST this evening for CAZ114-115. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PST this afternoon for PZZ470-475. && $$ 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

402 FXUS66 KMTR 202148 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 148 PM PST Mon Jan 20 2025 ...New SYNOPSIS, SHORT TERM, LONG TERM... .SYNOPSIS... Issued at 144 PM PST Mon Jan 20 2025 Strong, gusty winds continue over the North Bay and East Bay Hills where Wind Advisories will be in effect through 1 AM Tuesday. Cold mornings continue through late week with Frost and Freeze products likely to be reissued throughout the week. Daytime temperatures will see a slight warming trend Tuesday through Thursday before another pattern change takes place late week. && .SHORT TERM... (This evening through Tuesday) Issued at 144 PM PST Mon Jan 20 2025 Gusty winds have been observed across the Bay Area with peak gusts ranging from 66 mph to 72 mph. These winds have largely been concentrated over the interior North Bay Mountains where a Wind Advisory went into effect at 4 AM and will expire at 1 AM Tuesday. Gusty winds have additionally been observed in the East Bay Hills where a few stations are hovering right around Wind Advisory criteria. A few sites (PG914 and PG696) in the vicinity of Mt. Diablo State Park have been gusting to between 45 to 50 mph. With this in mind, a Wind Advisory has been issued beginning now through 1 AM Tuesday for the East Bay Hills with gusts between 35 to 50 mph possible. Diving deeper into our winds, the SFO-WMC pressure gradient was -12.40 hPa as of noon. This has weakened (slightly) from earlier in the morning when the gradient was -12.70 hPa at 10 AM PST. WRF guidance shows the pressure gradient begins will begin to weaken more significantly during the late evening hours which should coincide with winds starting to weaken. There is some uncertainty on when the gradient will switch from negative (offshore) to positive (onshore). The WRF shows the switch happening early to mid morning on Tuesday whereas the HRRR and GFS models both show it happening later Tuesday morning. Regardless, as the pressure gradient weakens winds will gradually ease over the Bay Area and drop below Wind Advisory criteria by very early Tuesday morning. Conditions are expected to remain clear overnight which brings us to our second hazard, a combination of Freeze Warnings and Frost Advisories. Frost Advisories have been issued for the interior Bay Area and Central Coast except for the southern Salinas Valley where a Freeze Warning has been issued instead. For the Frost Advisory, overnight temperatures are expected to drop as low as 33 degrees with particular emphasis on the Valleys and highest ridgelines. Given the clear skies anticipated overnight, additional radiational cooling is expected to occur overnight which will push more locations across the CWA into Frost Advisory territory. A Freeze Warning will be in effect overnight for the southern Salinas Valley where temperatures will drop as low as 26 degrees. Portions of the Fort Hunter Liggett area and far southeastern Monterey County may see locally colder temperatures dropping as low as 29 degrees. These areas are bordering the Southern Salinas Valley and Arroyo Seco zone. Cold mornings will continue through the week ahead with high confidence in the additional issuance of Frost Advisories and medium confidence in the additional issuances of Freeze Warnings over the upcoming week. && .LONG TERM... (Tuesday night through next Sunday) Issued at 144 PM PST Mon Jan 20 2025 For those of you who would prefer slightly warmer daytime weather and less breezy conditions, the next week is for you! The positively tilted upper level trough that has been digging into the West Coast (bringing our early week wind) continues to look fairly progressive and is expected to move eastward, away from the West Coast, on Tuesday. In its place a ridge of high pressure will build over the West Coast and bring with it clear skies and a gradual warming trend through the week ahead. Daytime temperatures will generally be in the 60s while the warmest portions of southern Monterey county may reach the low 70s. On the flip side, clear skies overnight will lead to additional radiational cooling and will continue to necessitate the issuance of Frost/Freeze products across the Bay Area and Central Coast. The most likely locations will be in the North Bay Valleys and the interior Central Coast. The pattern will again change late week as an upper level low slides into the western United States and deepens over CA, with the ECMWF showing the upper level low becoming cut-off over the Bay Area before moving southwards. While this system continues to trend fairly dry, it does look as though it will produce strong, gusty winds both over the marine environment and over the interior North Bay Mountains and East Bay Hills. High end small craft warnings are likely over the southern coastal waters while Gale Warnings are likely over the northern coastal waters. The NBM continues to show PoPs in the range of 30-40% along the Central Coast and lower PoP values across the Bay Area. If any rain does develop with this system, it is likely to be only drizzle directly along the coastline with particular emphasis on coastal Monterey County. Any rainfall that does accumulate on the Central Coast is likely to be less than a tenth of an inch, not meeting wetting rain criteria. CPC guidance highlights the weeks 3-4 outlook (February 1 - 14th) as when the return of above average precipitation is likely. && .AVIATION... (18Z TAFS) Issued at 936 AM PST Mon Jan 20 2025 High confidence in VFR through the TAF period once lingering stratus in the interior Central Coast valleys clears. Gusty offshore winds with gusts of 20-25 knots will continue through the day, with LLWS concerns diminishing as higher winds aloft mix down to the surface. Gusts will diminish late this evening with light offshore flow overnight. Vicinity of SFO... VFR through the TAF period. Northeast winds gusting to 20-25 knots continue into the evening, diminishing overnight and remaining light through Tuesday. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... VFR through the TAF period once the Salinas Valley clears out. Light onshore flow develops this afternoon, followed by offshore drainage flow this evening and overnight. && .MARINE... (Today through Saturday) Issued at 851 AM PST Mon Jan 20 2025 Offshore breezes prevail across the waters through Tuesday with strong to near gale breezes within the San Pablo and San Francisco Bays. Moderate seas will persist through Thursday with significant wave heights becoming rough by Friday. Gale force winds are expected Friday and into the weekend. && .BEACHES... Issued at 334 AM PST Mon Jan 20 2025 A Beach Hazards Statement is in effect for all Pacific Coast beaches through 7 PM as a long period westerly swell is resulting in a moderate to high risk of sneaker waves and an increased risk of rip currents. For beachgoers to remain safe it is vital to keep off of jetties and rocks, keep pets on a leash, observe the ocean for 20 minutes before recreating on the beach or in the ocean, and never turn your back on the ocean. Sarment && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement until 7 PM PST this evening for CAZ006- 505-509-529-530. Wind Advisory until 1 AM PST Tuesday for CAZ504-515. Frost Advisory from 1 AM to 9 AM PST Tuesday for CAZ504-506-510- 513>515-517-518-528. Freeze Warning from 1 AM to 9 AM PST Tuesday for CAZ516. PZ...Small Craft Advisory until 3 PM PST this afternoon for SF Bay N of Bay Bridge. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy AVIATION...DialH MARINE...DialH 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

499 FXUS66 KOTX 201733 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 933 AM PST Mon Jan 20 2025 .SYNOPSIS... A cold weather pattern will persist through the middle of the week. There is a small chance of flurries Tuesday morning. Temperatures gradually return to more seasonal levels late this week with chances for snow Thursday and Friday. && .DISCUSSION... Today through Wednesday: Aaahhhhh, that sun felt so good yesterday even though it was chilly. But the clear skies continued though the night and this morning, which has led to our coldest temperatures so far this winter. As of 2 am, we are seeing many single digits across the north, with teens to around 20 elsewhere. Winthrop even dipped to -1 briefly after midnight. There are some clouds along Lake Chelan and across north Idaho around Sandpoint and Bonners Ferry, which have kept their temps `warmer` in the teens. The ridge will begin to flop over and temporarily flatten this afternoon ahead of a wave that will move into the region overnight and Tuesday. High clouds will move in from northwest to southeast this afternoon and evening. The wave isn`t particularly strong, and it is very dry across the region. Most locations will just see an increase in clouds, which will keep our temps several degrees warmer for Tuesday morning. Some of the high resolution models are showing some potential radar returns as this wave moves through. Agree with the NBM in showing no or very low probabilities of measurable precipitation. However, given what the hi res stuff is showing, I put in some flurries overnight through Tuesday morning for much of the region. Impacts would be incredibly low. Once that wave moves to the east, the ridge pumps back up offshore for Wednesday. Clouds will decrease which will bring another morning of cold temps across the region. Temps will generally be 10-20 degrees, but cannot rule out some of the northern valleys getting into the single digits Wed morning. Thankfully winds remain light through the period. /Nisbet Wednesday night through Sunday: Upper level ridge axis oriented to the west allows for a cold and generally dry northwest flow to continue Wednesday night however ensembles suggest an increase in pops and QPF for snow Thursday and Friday as a disturbance with a weak moisture source drops down in this same flow from north to south. Significant snow accumulation is not expected in this Thursday/Friday period. Remainder of the weekend is expected to be generally clear, dry, and cold as the ridge amplifies with same axis placement offshore and allows for a return to a cold and dry flow from the northeast. /Pelatti && .AVIATION... 18Z TAFS: VFR conditions for all TAF locations through the period. High clouds will move over the ridge this afternoon ahead of the next weak weather system to move in Tuesday. Satellite is looking pretty clear across the region, except for parts of Lake Chelan and north ID generally SZT northward. Cigs for Bonners Ferry and SZT are btwn 3-5k ft. Kept mention of some shallow shallow or patches of fog for GEG/SFF/COE, but have removed the idea of it lifting into a stratus deck given trends so far this morning. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate confidence with current TAFs. Low confidence of fog developing, or lifting into a stratus deck. There is a small chance (10% or less) of flurries moving into the region aft 08Z Tues. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance && .PRELIMINARY POINT TEMPS/POPS... Spokane 26 19 30 16 30 19 / 0 0 0 0 0 0 Coeur d`Alene 26 17 31 14 31 17 / 0 0 0 0 0 0 Pullman 27 19 31 19 34 23 / 0 0 0 0 0 0 Lewiston 33 24 38 23 38 27 / 0 0 0 0 0 0 Colville 23 13 27 11 28 15 / 0 0 0 0 0 0 Sandpoint 23 17 28 17 29 19 / 0 0 0 0 0 0 Kellogg 25 18 29 14 32 19 / 0 0 0 0 0 0 Moses Lake 29 21 34 20 35 22 / 0 0 0 0 0 0 Wenatchee 28 19 34 22 33 23 / 0 0 0 0 0 0 Omak 25 16 28 16 29 18 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

862 FXUS66 KPDT 202209 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 209 PM PST Mon Jan 20 2025 .SHORT TERM...Today through Wednesday... Bottom Line Up Front 1. COLD!!! 2. Breezy winds through the Grande Ronde Valley Current satellite shows scattered high clouds moving over portions of the region with mostly clear skies elsewhere. Current ground observations show that very few places are above freezing at this time. A few localized areas in the Basin, Gorge and central OR being the exception. Models are in firm agreement with the leading edge of the upper level high pressure system parked over the region. Northwest flow aloft is what is bringing in the below freezing temperatures and coupled with clear skies will allow overnight temperatures to dip below freezing across the vast majority of the region. This will assist with keeping overnight temperatures tonight cold. Model guidance as well as ensembles indicate the region will remain subfreezing overnight each night through Wednesday night. Over 80% of the raw ensemble guidance shows that the Pendleton area will see temperatures between 20-25 degrees, 50-80% shows the Basin seeing 20- 30 degrees, central and north central OR seeing 15-25 degrees, the Gorge seeing 20-30 degrees and the Yakima/Kittitas Valleys seeing 20- 25 degrees. NBM shows the Wallowa Valley, especially near Enterprise seeing temperatures in the negatives as well as areas near Seneca. Confidence in the overall forecast for overnight temperatures being subfreezing high (90%). Now lets chat about highs, highs today will barely crest above freezing for many areas with the exceptions being some localized areas of the Basin, Gorge and central OR. As we move to tomorrow, models and ensembles do show there to be a slight increase in daytime temperatures from today. However, only 56% of the raw ensembles seem to agree temperatures will be in the upper 30s through the Pendleton area, 44% agree temperatures will be in the low 30s. Moving to central OR, 87% of the ensembles agree the region will see upper 30s to low 40s. 61% for the Gorge seeing upper 30s to low 40s and 35% for 40 to 45 degrees. 40% agree the Basin between 30-35 degrees, 40% agree 35-40 degrees while the remaining ensembles have temperatures below 30 degrees. Yakima/Kittitas Valleys roughly 50% of the ensembles agree temps will be 35-40 degrees with the other 50% showing temperatures below 35 degrees. Confidence with the high temperatures to be moderate (50-70%). Models show a brief shortwave disturbance will ripple across the leading edge of the high assisting in flattening the ridge a bit. This will briefly shift the winds to a westerly pattern. Looking the surface pressure gradients, there is a clear tightening along the Grande Ronde Valley. Pressure gradient are not tightened enough to warrant an advisory, however, 70-90% of the raw ensembles do show wind gusts of 30-40 mph occurring beginning later this evening and persisting through the early morning. Otherwise, models show the shortwave exiting the region early Tuesday morning and the leading edge of the upper level ridge moving back in overhead bring northwest flow aloft and winds returning to near 10 mph through Wednesday. Bennese/90 .LONG TERM...Thursday through Monday...Continued ridging on Thursday will produce dry conditions through Thursday afternoon, with slightly above normal temperatures. There is good agreement in guidance that a wave of low pressure will sweep into the PacNW Thursday evening. This cold front will move moisture over the mountainous areas (Cascades and Blue Mountains) producing moderate chances (40-60%) of snowfall above 1500-2500 ft. As the front progresses on Friday, much of the forecast area will see chances (20- 50%) for precipitation with snow levels decreasing to below 1000 ft. Through Friday afternoon, the Blue Mountains are anticipated to receive the greatest snowfall amounts with values between 2 and 5 inches of snowfall (probabilities demonstrate a 40-60% chance of 2 inches, with a 20-30% chance for up to 4 inches). The Washington Cascades will see between 1 and 4 inches, with the highest amounts noted around Snoqualmie Pass where there will be a low chance (15- 35%) of snowfall of 2 inches, dropping to <10% chance for up to 4 inches. The front will move south of the area by late Friday night, with drier conditions noted by Saturday late morning/early afternoon. As this system departs, there will be a return of ridging, with generally dry conditions. Light additional snowfall is expected through early Saturday morning with less than an inch seen across central Oregon except around the southern Oregon Cascades where up to 2 inches favored (30-40% chance). Brief periods of gusty wind could accompany the frontal passage, with gusts 15 to 20 mph forecast. Temperatures will continue to cool on Saturday, which is expected to be the coldest day in the extended period. As mentioned previously, Thursday will see temperatures above normal across much of Oregon, with cooler than normal temperatures noted across the Columbia Basin through Washington. After the frontal passage on Friday, temperatures will dip to 5 to 10 degrees below normal for much of the forecast area, with values almost 15 degrees cooler than normal over portions of the Blue Mountains. With further cooling on Saturday as the system dives further south, temperatures will cool an additional 5 to 10 degrees dipping to values of 10 to 15 degrees below normal. On Saturday, there much of Oregon will see a high chance (70-90%) for maximum temperatures to be 32 degrees or lower, with a 20-40% chance of high temperatures reaching only up to 28 degrees. Sunday and Monday will see a slightly warmer temperatures, though the majority of the area will remain 5 to 10 degrees below normal through Monday. Overall cluster analysis is in fair agreement through the extended time frame with the progression of the incoming system. Some variances in timing and intensity are present, but the overall pattern is generally agreed on. Branham/76 && .AVIATION...00z TAFs...Widespread VFR. Dry conditions and light wind are expected through the period. A weak, dry wave will move quickly through the area Tuesday morning/afternoon, which may produce a few clouds over the higher terrain. Branham/76 && .PRELIMINARY POINT TEMPS/POPS... PDT 22 39 22 37 / 0 0 0 0 ALW 23 38 23 37 / 0 0 0 0 PSC 25 37 24 36 / 0 0 0 0 YKM 18 37 20 36 / 0 0 0 0 HRI 25 38 24 37 / 0 0 0 0 ELN 18 38 22 36 / 0 0 0 0 RDM 21 47 21 45 / 0 0 0 0 LGD 18 37 18 40 / 0 0 0 0 GCD 18 42 20 44 / 0 0 0 0 DLS 26 44 28 41 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...90 LONG TERM....76 AVIATION...76

163 FXUS65 KREV 201844 AFDREV Area Forecast Discussion National Weather Service Reno NV 1044 AM PST Mon Jan 20 2025 .SYNOPSIS... * Cold and dry today with gusty winds along the Sierra crests. * Warming up Tuesday through Friday, with continued dry conditions, light winds, and inversions. * A pattern change by the weekend with colder temperatures, breezy winds and possible snow showers. && .DISCUSSION... Overnight lows hovered just below 20 degrees across much of the region, with even colder air positioned to our east. Our high temperatures will struggle to exceed 40 degrees for even our warmest sites today. Coupled with the increasing winds overnight that brought gusts 75 to 85 mph already this morning along Ward Peak. We expect winds to persist and even increase slightly into the afternoon and evening hours. After sunset, winds should begin to taper. With light winds and clear skies during the overnight hours, tonight`s low temperatures are expected to fall a bit lower than last night`s. Tuesday brings in more of the same in terms of clear skies and light winds, which will introduce a warming trend through the end of the week. This will bring a gradual warming trend that will have our temperatures ranging 5-10 degrees above average by the end of the week. For the weekend, a trough is positioned to drop in from a continental polar air mass over Canada which looks to phase with a weak low over the Pacific. Some ensembles are bringing the center of circulation into our region by way of the Pacific Coast and Central Valley, while others bring the low center in over the Great Basin. This discrepancy in track will matter for detail such as precipitation amounts, wind direction and speed, and how much cold air we see. If the second scenario pans out, we would see a much colder north to east wind, if the first wins, we would see southwesterly flow, which would moderate the cold air intrusion. For all these reasons, we are confident in the appearance of this disturbance this weekend, with Saturday looking to be the day with the most widespread impacts. Forecast confidence is much lower in terms of the details, but as we move forward through the week, the details will become more clear. HRICH && .AVIATION... * VFR conditions at all western Nevada and Sierra terminals today. * Ridge winds continue to increase this afternoon, with maximum gusts to 65-75 kts. Expect LLWS for KTVL/KTRK and mountain wave turbulence along and west of the Sierra crest. McKellar/HRICH && .REV Watches/Warnings/Advisories... NV...Lake Wind Advisory until 7 PM PST this evening NVZ002. CA...Lake Wind Advisory until 7 PM PST this evening CAZ072. && $$

753 FXUS66 KSTO 202027 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1227 PM PST Mon Jan 20 2025 .SYNOPSIS... Gusty winds are expected through this evening before returning to dry weather and cold, foggy mornings over the next several days. && .DISCUSSION... Gusty winds are ongoing across NOrthern California, mainly 20-35 MPH, up to 45 MPH over the higher terrain of the foothills and Sierra. These winds will continue through this afternoon before trending down first in the Valley then elsewhere by early Tuesday AM. After Tuesday, ridging remains the dominant weather feature with troughing much further east, reducing the gradient and relaxing our winds over the next several days. This will keep things relatively quiet outside of cold mornings and patchy fog/frost. Valley lows are expected to be in the 30s through midweek with several sites at or near freezing, from roughly south of Yuba City or I-80 broadly. NBM chances show a 30-50% chance of temperatures below freezing tomorrow morning across parts of the Central Valley , highest along the eastern portions of the Valley and from the Delta to the Greater Sacramento Area. Additionally, models show just a 10-30% chance of dense fog tomorrow so conditions point to a less widespread fog development if anything in comparison to the previous nights. Valley highs will be in the upper 50s to low 60s each day with cooler temps as you increase in elevation. Hope you all had a restful holiday/holiday weekend! && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Inside slider short wave trough predicted to drop into Interior NorCal Friday night into the weekend. Showers will be possible, mainly in the northern and eastern foothills with snow showers in the mountains during this period though amounts will be light. Currently, the NBM only shows a 40-60% chance of 0.25" or greater of precipitation at this time. Slight chance of showers (15-30%) in the Central Valley Saturday south of I-80. Additionally, this will bring breezy to windy conditions with cooler temperatures close to freezing in parts of the Valley. Drier weather returns early next week as the short wave trough pushes south of the CWA and upper ridging from the Pacific builds into NorCal. && .AVIATION... Areas of MVFR/IFR conditions with locally LIFR conditions in BR/FG are expected in Southern Sacramento and Northern San Joaquin Valleys and Delta after 04Z, otherwise VFR over interior NorCal next 24 hrs. In Central Valley, widespread northernly surface winds are forecast to be 15-20 kts with gusts to 25 kts through 04Z Tuesday. Surface winds are forecast to be 15-25 kts with local gusts up to 40 kts over foothills and mountains. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

004 FXUS65 KMSO 202115 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 215 PM MST Mon Jan 20 2025 .DISCUSSION... KEY MESSAGES: - Unseasonably cold through tonight. - Widespread light snow event Friday followed by an arctic intrusion into the weekend. The arctic air pushed into the region as expected for the most part. Some locations that kept a breeze going overnight weren`t able to get that cold (i.e. Leadore Idaho saw a 9 below temperature, but could have been colder). Lows between 20 and 30 below zero were common in the higher valleys along and west of the Continental Divide. Someone that lives between Feely and Divide near I-15, south of Butte reported to us on Facebook a low of 33 below! A private station on the west side of Georgetown Lake reported a low of 29 below zero. There is a fair amount of high clouds streaming southwards from British Columbia this afternoon. There are also signs of breaks in the clouds further upstream. This will play into what kind of temperature trends we`ll see this evening once the sun goes down. Some locations may be able to see temperature drops, and some of the higher valleys may be able to get down below 10 below or colder. Though we don`t have any cold advisories issued, keep in mind that there may be enough wind along the Divide to bring wind chills down to 20 below in places this evening. There is high confidence that an upper level trough will dive south over the region later Thursday into Friday. While the valleys may get a dusting to a couple of inches of snow, the mountains from Idaho County, to the Missions and Bob Marshall, have a 50 to 70 percent probability of getting 2 inches or greater. There is a 80 percent probability that another arctic airmass will bring colder temperatures for next weekend. The lower percentiles (lowest outliers) depict the potential for going below zero, between 10 to 20 below zero, along and west of the Divide between Saturday(Jan. 25) and Monday(Jan. 27). && .AVIATION...Stable conditions and light winds are expected tonight. Stratus has developed across northwest Montana and may periodically result in MVFR ceilings with a few flurries as mid level moisture will also stream over it. A weak disturbance on Tuesday will enhance opportunities for light snow showers, especially on the terrain and once again focused north of I-90. By Tuesday afternoon, gusty westerly winds of 15-25 kts will be felt across southwest Montana. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

010 FXUS65 KBOI 202118 AFDBOI Area Forecast Discussion National Weather Service Boise ID 218 PM MST Mon Jan 20 2025 .SHORT TERM...Tonight through Wednesday night...Little change in the dry stable weather pattern with an upper ridge off the west coast and a north-northwest flow aloft across our region. Temperatures remain cold, but with a slight warming trend. The air mass is too dry to support fog, but there may be localized pockets of early morning fog in wind-sheltered mountain valleys. .LONG TERM...Thursday through Monday...Models are in decent agreement with regard to a developing upper trough moving from from the north late in the week. However, there is some disagreement with the strength and southward progression of it. A blend of ensemble members depict a faster-moving system which would keep snowfall amounts on the lighter side. There is a 15-40 percent chance of light snow in the valleys and a 40 to 60 percent chance in the mountains on Friday with the trough passage, followed by a 15-30 percent chance of light snow in s-central Idaho and along the Nevada border on Saturday. A cold front will accompany the trough, providing the region with breezy to locally windy conditions - especially on Saturday. Drier stable conditions with light winds follow early next week as another upper ridge develops off the coast. Near-normal temperatures Thursday and Friday lower to several degrees below normal over the weekend and into early next week. && .AVIATION...VFR with sct-bkn high level clouds. Surface winds: variable up to 10 kt. Winds aloft at 10kft MSL: N 15-30 kt. KBOI...VFR with sct-bkn high level clouds. Surface winds: mainly SE up to 10 kt. && .AIR STAGNATION...An upper ridge will remain just off the west coast through Thursday, but with mixing heights generally below 2000 feet AGL from Tuesday through Thursday. A weak upper level trough passing by to our east will enhance the winds in the mixed layer in most areas on Tuesday, followed by lighter winds less than 10 mph Wednesday through Thursday. A stronger trough will provide better mixing that will scour out the inversion on Friday. && .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...BW LONG TERM....BW AVIATION.....BW AIR STAGNATION...BW

048 FXUS65 KLKN 202104 AFDLKN Area Forecast Discussion National Weather Service Elko NV 104 PM PST Mon Jan 20 2025 .SYNOPSIS...High pressure will remain stationed off the west coast of the United States through the short term. This will mean a continuation of dry weather for the upcoming week. Temperatures will begin a slow warm up Tuesday through Friday. Look for our first chances for light precipitation, in the form of snow showers, beginning late Friday through the weekend. && .SHORT TERM...Tonight through Tuesday night. Skies remain mostly sunny this afternoon under a northerly flow aloft. Upper level high pressure ridge remains stationed off the western coast of the United States. For tonight, conditions will remain mostly clear, with light winds chilly temperatures in the single digits and teens. Some of the colder locales could see lows below zero. Here are some probabilities of low temperatures 5 degrees or less for select locations across northern and central Nevada for the morning of January 21, 2025: Austin - 0% Battle Mountain - 20% Elko - 40% Ely - 100% Eureka - 4% Jackpot - 80% Jarbidge - 0% Owyhee - 0% Ruth - 40% Spring Creek - 30% Tonopah - 0% Wells - 85% West Wendover 20% Wildhorse Res - 80% Winnemucca - 20% For Tuesday and Tuesday night, an upper trough is forecast to move down the eastern side of the ridge and will brush northeastern Nevada Tuesday. No precipitation is expected at this time as the energy and moisture remains in Montana. Highs will modify slightly with readings generally in the 40s over the area. Winds will be light over much of the area though some breezy gusts to 20 mph are possible in the northern sections of Nevada along the Idaho border. Quiet weather will continue through the overnight on Tuesday with light winds and low temperatures in the teens. .LONG TERM...Wednesday through next Monday A gradual warming trend is expected by mid to late next week as a ridge of high pressure strengthens over the eastern Pacific. Highs will reach into the upper 40s to lower 50s with overnight lows ranging from the teens to 20s. Skies will be partly to mostly clear, and winds will remain light, staying below 10 mph throughout the period. The probabilistic ensemble guidance are gradually converging on the arrival of the next trough late next week. A strong cold front will move through the region Friday through Saturday, bringing increased west-northwest winds at 10 to 15 mph, with gusts of 25 to 30 mph. Additionally, this system is expected to bring light snow showers across the forecast area. Snowfall amounts are expected to range from 1 to 2 inches in most valleys, while the mountains in central Nevada, primarily south of US-50, are forecast to receive 2 to 6 inches Saturday through Sunday night. Below are the probabilities of an inch or more of snowfall at select locations in northern and central Nevada for January 25-26th, 2025. Austin - 35% Battle Mountain - 30% Elko - 35% Ely - 50% Eureka - 50% Pequop Summit - 60% Spring Creek - 50% Tonopah - 40% Wells - 55% West Wendover 10% Winnemucca 20% With colder air accompanying the trough passage, there is high confidence that temperatures will drop to near or below normal for this time of year. Below are the probabilities of low temperatures reaching 10 degrees or less at select locations in northern and central Nevada on the morning of January 27, 2025: Austin - 25% Battle Mountain - 55% Elko - 60% Ely - 90% Eureka - 50% Jackpot - 75% Jarbidge - 55% Owyhee - 50% Ruth - 65% Spring Creek - 70% Tonopah - 25% Wells - 65% West Wendover 35% Wildhorse Res - 80% Winnemucca 55% Quiet and dry conditions will return Monday as a Rex block pattern sets up over the western U.S., featuring a ridge of high pressure situated above a low pressure system to the south. This pattern will maintain northeasterly flow, bringing mid to high- level clouds across the forecast area. && .AVIATION...VFR conditions are expected at all terminals over the next 24 hours. Typical drainage flow of 10 kts or less will develop at KELY and KTPH starting around 02Z Tue. Scattered to broken clouds with ceilings ranging from FL150 to FL250 will persist from tonight through Tuesday. Winds on Tuesday will range from south to west at 5-10 kts at KEKO and KWMC, while remaining light and variable at other terminal sites. AMD NOT SKED for KTPH due to wind sensor issues. && .LKN Watches/Warnings/Advisories... None. && $$ 86/90/90