ZSE Aviation Forecast Discussions

199 FXUS66 KSEW 220415 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 815 PM PST Fri Feb 21 2025 .SYNOPSIS...An atmospheric river will set up over Western Washington making for a very wet weekend. The river will move out of the area Sunday night. After a brief break early Monday a front will move through later Monday into early Tuesday for another round of rain as well as locally windy conditions. An upper level ridge will try and build in the middle of next week but systems nearby will keep a chance of rain at times Wednesday through Friday especially for the coast. && .SHORT TERM /TONIGHT THROUGH TUESDAY/...The bulk end of the first wave of precipitation is beginning to move into the Cascades, but conditions still remain very wet throughout Puget Sound, with additional showers along the coast. A recent look at the newest QPF forecast does show some minor increases along the windward side of the Olympics and portions of the Cascades, but the full forecast will be run and updated overnight. Otherwise, no significant changes have been made and an update to the aviation and marine section can be found below. An atmospheric river is aimed at Western Washington for the weekend. Leading edge of the initial slug of moisture reaching the coast Saturday morning, spreading inland to the Cascades by late morning. Winds in the lower levels of the air mass increasing with model 850 mb winds showing a core of southwesterly 50 to 60 knots over the Southwest Interior and along the coast. Southerly winds at 850 mb over the North Cascades will give that area less precipitation than the remainder of the Cascades under the southwesterly winds aloft scenario. Snow levels rising up to as high as 7000 feet by late afternoon. Even with rain most of the day highs will be mild, in the lower to mid 50s. Atmospheric river remaining over Western Washington Saturday night. Vertically Integrated Water Vapor Transport ( moisture content ) numbers the highest during this time frame with models indicating 1000-1200 kg/m/second. A sustained round of these values is a strong indicator of river flooding for the area. In this case the values peak Saturday night into Sunday morning then ease during the day Sunday. Rainfall amounts of 1.5 to 2 inches in the 12 hour period between 00z to 12z Sunday ( 4 pm Saturday to 4 am Sunday ) for the mountains and along the coast with 0.50 to 1.25 inches over most of the lowlands. Lower rainfall amounts for the interior forecast over the Northwest Interior. With the strong southwesterly flow aloft the rainshadow will be in its usual place with Sequim and Port Townsend only getting around a quarter of an inch. Lows in the mid 40s to lower 50s. Atmospheric river sagging south Sunday morning with rainfall rates decreasing over Western Washington. Rain increasing again Sunday afternoon as the river lifts back up over the area. Highs in the mid 50s. Front/back end of the atmospheric river moving through Western Washington later Sunday night into early Monday morning bringing about an end to the steady rain. Lows in the 40s. After a brief break Monday morning another weather system approaches the area Monday afternoon. Parent low with this feature, a 980-985 mb low, will reach 130W due west of the area then make a northeasterly turn. This will in turn increase the negative tilt of the front slowing its northerly progress down with the front stalling over Western Washington in the afternoon. With the low that far west best chances for gusty/possible advisory speed winds, along the coast and the Northwest Interior late in the day. Highs again in the lower to mid 50s with rain all afternoon. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Extended models in pretty good agreement with the front kicking out to the north early Tuesday followed by a weak upper level trough later in the day. Upper level trough digging south between 130-140W which will in turn pump an upper level ridge up along the coast Wednesday. Warm front trying to move through the top of the ridge and with the cold front well offshore Western Washington will be in the warm sector. This has the potential to be the warmest day of the season with highs near 60 in the warmest locations. Trailing cold front trying to move through the ridge Thursday before the ridge rebuilds Friday. Operational runs showing good amplitude to the ridge but the ensemble solutions are not as strong. This keeps a chance of rain at times in the forecast Wednesday through Friday with the best chances along the coast and over the Northwest Interior. Mild air mass remaining over the area with highs Thursday and Friday in the mid 50s to near 60. Felton && .AVIATION... Ceilings will lower to MVFR tonight and look to remain there through the remainder of the TAF period. Southeasterly winds will increase tonight ahead of the frontal system, with the strongest winds (up to 12-15 kt) in the north interior. Winds remain south to southeasterly tomorrow and will begin to increase area-wide tomorrow afternoon as another round of rain begins to approach the region. KSEA...Ceilings have lowered to MVFR in recent observations and are expected to persist in the wake of this first pulse of moisture and persisting through the remainder of the TAF period. Southeasterly winds will remain around 7 to 10 knots through tonight and will begin to continue to increase tomorrow afternoon at the end of the TAF period. As the front passes, there is LLWS potential, but confidence is too low and the event too far out to be considered in this TAF package, but will be evaluated throughout the night. 62/Kristell 62 && .MARINE...A frontal system will continue to move onshore tonight into early Saturday morning, with a series of frontal systems traversing the area waters Saturday and late Sunday. This will keep conditions active across the area waters. Small Craft Advisory conditions will continue across the coastal waters today, with a brief break tonight before winds restrengthen on Saturday, reaching low-end gale force by Saturday afternoon. Through the interior waters, southeasterly winds will strengthen through Admiralty Inlet, the East Entrance to the Strait of Juan de Fuca, and through portions of the Northern Inland Waters. There will also be a brief break early tomorrow morning before winds strengthen again Saturday afternoon into early Sunday. There may be some gusts to gale force through the East Entrance on Saturday, but sustained winds should remain in the Small Craft range. Winds look to ease below thresholds across the interior waters on Sunday but remain elevated over the coastal waters with the system on Sunday farther offshore. A stronger low pressure system looks to develop over the northeast Pacific and move northeastward towards Vancouver Island Monday night into Tuesday. There still remains considerable uncertainty on the strength and track of this system, but a period of gale to potentially storm force winds remain possible during this period. High pressure looks to develop over the Pacific Northwest by the middle of next week, for a period of calmer conditions. Seas will slowly build this evening to around 12 to 15 ft tonight. Seas will increase and subside with each passing system this weekend but generally remain in the 12 to 15 ft range. The stronger system Monday into Tuesday may push seas over 20 ft Monday night. Seas will slowly subside after Tuesday but look to remain above 10 ft through at least mid-week. 62 && .HYDROLOGY...A series of systems including an atmospheric river will move through the area into Tuesday. This has increased the potential for river flooding, urban flooding, and landslides. Snow levels will increase to above 7000 feet Saturday night into Sunday, with heavy rain falling over the Cascades and Olympics. These mountain ranges will likely see 3 to 5 inches of rain, with locally higher amounts possible. A few of the rivers remain on track to reach flood stage at some point over the weekend into next week. The flood watch for Mason County was upgraded to a flood warning for the Skokomish River at Potlatch (moderate flooding forecasted). A flood watch for Sunday morning through Tuesday was issued for Grays Harbor, Lewis, Thurston, Pierce, King, Snohomish, and Skagit Counties based on the 10-15% increase in QPF over these areas. Several of the rivers expected to go well above action stage (Snoqualmie at Carnation is projected to go into minor flood Monday morning). A flood potential outlook remains for Jefferson, Clallam and Whatcom counties. Flood potential is too low for these areas to be included in the flood watch. There is still the possibility of urban flooding across all of the area with the best chance Saturday night into Sunday morning. Please continue to monitor the forecast for any potential changes to the precipitation outlook through the weekend, and for any headline changes. HPR && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Flood Watch from Sunday morning through late Tuesday night for Bellevue and Vicinity-Central Coast-East Puget Sound Lowlands-Everett and Vicinity-Lower Chehalis Valley Area- Olympics-Seattle and Vicinity-Southwest Interior-Tacoma Area-West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes-Western Skagit County. Wind Advisory from 10 AM to 7 PM PST Saturday for Central Coast- North Coast. PZ...Small Craft Advisory until 7 PM PST Saturday for Admiralty Inlet- East Entrance U.S. Waters Strait Of Juan De Fuca-Grays Harbor Bar-Northern Inland Waters Including The San Juan Islands-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 4 AM PST Saturday 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. Gale Warning from 4 AM to 7 PM PST Saturday 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. && $$

389 FXUS66 KPQR 220606 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 1000 PM PST Fri Feb 21 2025 Updated aviation discussion. .SYNOPSIS...A series of frontal systems will impact the Pacific Northwest through the weekend and into early next week. A weak one tonight will be followed by multiple this weekend and Monday associated with moderate to strong atmospheric rivers. These systems will be very wet and bring heavy rainfall. Localized flooding, especially along the coast, is possible. Gusty winds are also expected Sunday and Monday. Additional rain is possible mid to late next week, but confidence is lower in details at this time. && .SHORT TERM...Friday afternoon through Monday...Satellite imagery early Friday morning shows the weak front approaching the West Coast as well as the stream of moisture over the central eastern Pacific associated with an atmospheric river that will impact Oregon and Washington this weekend. Very light radar returns are moving onshore this afternoon and are only expected to produce light showers mainly in SW Washington and the far northern Oregon coast this afternoon. The main rain band with this first front will push through the region overnight, turning to scattered showers early tomorrow morning. Very scattered showers will continue through most of the afternoon tomorrow with many areas in the inland lowlands seeing very little to no rain. Overall, limited rain amounts are expected through tomorrow afternoon, generally a few hundredths to 0.15 inch in the interior lowlands, Oregon Cascades, and central Oregon coast, and 0.25-0.5 inch for the northern Oregon coast and Coast Range and SW Washington Cascades. The main event starts Saturday late afternoon/evening as a moderate to strong atmospheric river (AR) takes aim at Oregon and Washington through Sunday night quickly followed by another moderate yet shorter lived atmospheric river on Monday. There will be very little break in the rain between these events, with steady rain over the weekend decreasing to showers briefly Monday night before steady rain returns again Monday morning. As such, will discuss rain amounts in one 72 hour period from 4 am Saturday to 4 am Tuesday. Some hefty rain amounts are possible over the northern Oregon Coast Range and SW Washington/far northern Oregon Cascades with a 50-70% chance of 5 inches of rain. Localized areas could see up to 6 inches due to orographic lift. Coastal areas and the rest of the Coast Range and Cascades have a 60-90% chance of reaching at least 3-4 inches of rain. Inland lowlands will see a 60-80% probability of closer to 2-3 inches of rain. The heaviest bursts of near constant moderate to locally heavy rain are expected basically from 4pm Saturday to 4pm Sunday and again Monday morning with lighter rain in between. There is a concern with localized urban flooding, especially for low lying areas and roadways, especially later Sunday and Monday. Additionally, flooding concerns of certain Coast Range and Coastal rivers has increased to around 20-50% chance of minor flooding, including the Wilson near Tillamook, the Grays, the Siletz at Siletz, and the Luckiamute near Suver. People near these locations should keep an eye on the forecast and make any necessary preparations. Additionally, these ARs will usher warm Pacific air into the region, causing snow levels to rise well above pass level Saturday into Monday. Therefore, limited snowfall is expected. Wind is the other main concern with these ARs. Winds will shift southerly tonight and increase along the coast beginning Saturday afternoon, peaking Sunday. Expecting wind gusts up to 30-40 mph along the coast and gusts up to 45-55 mph at beaches and headlands. Valley lowlands will likely see wind gusts up to 25-30 mph, with infrequent gusts up to 35-45 mph possible. Winds will decrease Sunday night before picking up again on Monday afternoon and evening with similar gusts to Sunday. As soils become saturated due to continued rainfall, impacts such as downed weakened or dead trees are possible, especially on Monday when soils will be most saturated. -HEC .LONG TERM...Tuesday through Thursday...Relatively zonal flow expected on Tuesday, with possibility of showers remaining. That said, possibility of elevated winds remaining throughout Tuesday, though with significant uncertainty due to the uncertainty in timing of the system on Monday. NBM 90th percentile of wind gusts on Tuesday morning shows southwesterly 25-30 mph gusts remaining throughout the wider area. Heading into Wednesday, strong ensemble cluster guidance regarding ridging building into the region, potentially lasting for an extended period of a few days. Trending drier and warmer during this period, though light showers at times are not out of the question. /JLiu && .AVIATION...Observations from 06z Sat showed light rain developing over western WA and northwest OR with an incoming front. Cigs remained VFR, except MVFR along the north coast, including KAST. Cigs are forecast to fall to MVFR along the central OR coast by 08z Sat, and low-end VFR (around 4-5 kft) in the Willamette Valley as the front pushes inland. It appears there will be a break in precip from 12-18z Sat, aside from a few isolated light showers. MVFR cigs will become more widespread towards 00-03z Sun as widespread stratiform rain redevelops over the area, except IFR at the coast. There will also be strong low level wind shear along the coast Sun afternoon around 45-55 kt at 2000 ft. Surface winds will generally be southerly for most terminals, strongest at the coast on Sun with gusts up to 30-35 kt. Meanwhile, KTTD-KDLS offshore gradients will support easterly winds continuing through the Columbia River Gorge and into the eastern Portland Metro, with gusts 20-25 kt throughout most of the 06z TAF period. PDX AND APPROACHES...Cigs should generally remain VFR, except between 12-15z Sat when there is a 40% chance for cigs below 3000 ft. Much higher chance for MVFR cigs around and after 03z Sun (90% chance). Southeast winds 5-15 kt will become a bit gustier Sat afternoon and evening with gusts up to 20-25 kt. Winds will also veer to the south during that time. Expect periods of light rain between 06-12z Sat, then mainly dry weather between 12-21z Sat, then steadier rain after 21z Sat. -TK && .MARINE...A series of systems will lead to active weather across the waters this weekend into early next week. The first frontal system will push through tonight into early Saturday morning, bringing breezy southerly winds with gusts up to 30 kt. Seas will also build around 12 to 16 feet at 15 seconds as a westerly swell moves in. Therefore, the Hazardous Seas Warning remains in effect through Saturday morning for all waters including the Columbia River Bar. We`ll see a brief lull in marine conditions between 4-10 AM Saturday, however, it`s not a long enough time period to downgrade the Hazardous Seas Warning before winds and seas ramp up again. A more robust frontal system will arrive late morning/early afternoon Saturday, which will bring stronger southerly winds 25 to 35 kt with gusts up to 40 kt through early Sunday morning. Waves will become more wind-driven during this time while the westerly swell subsides, but combined seas remain around 13 to 17 feet at 13 seconds. Following this system, another break arrives between Sunday afternoon and mid-morning Monday. Guidance is trending toward another strong system that will bring gale force sustained winds with gusts up to 45 kt starting Monday afternoon. Will note that there is a 10-20% chance for storm force gusts of 48 kt or greater with this system, and a 30-40% chance that combined seas reach 20 feet or higher Monday evening. -Alviz && .HYDROLOGY... A series of frontal systems will bring heavy rainfall to northwest Oregon and southwest Washington this weekend and potentially Monday. Rain will begin Saturday afternoon, and intensify overnight through Sunday. This will lead to rises on rivers and creeks, especially along the coast on February 22nd through the 23rd. Main stem rivers may be delayed to respond, and flooding may occur beyond this time frame. There is around a 20-25% chance of the Wilson River, the Grays River, and other localized quick responding coastal rivers of reaching minor flood stage on Sunday and potentially Monday. Confidence in flooding is low as the location of heaviest precipitation will greatly depend on where the warm front sets up. In the case that this system over performs, more widespread flooding is possible. Heavy rainfall along the Cascades is expected and combined with recent snow accumulation, there is elevated landslide risk. Heavy rainfall may also lead to ponding of water, general lowland flooding, and localized urban flooding, especially in low-lying areas or other poor-drainage areas. Heavy rainfall will also increase the potential for landslides in areas of steep terrain and debris flows over areas that have been burned by wildfires over the past few years. -Hall/Muessle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Hazardous Seas Warning until 7 AM PST Saturday for PZZ210- 251>253-271>273. Gale Warning from 7 AM Saturday to 7 AM PST Sunday for PZZ210- 251>253. Gale Warning from 7 AM Saturday to 4 AM PST Sunday for PZZ271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

237 FXUS66 KMFR 220555 AFDMFR Area Forecast Discussion National Weather Service Medford OR 955 PM PST Fri Feb 21 2025 .DISCUSSION...Updated Aviation and Marine sections... && .AVIATION...22/06Z TAFs...VFR conditions are present across the area. Mid-level clouds will lower tonight as a frontal system offshore approaches. Light rain is moving east that is currently in Douglas County, but rain chances at both Medford and Klamath Falls are 20% or less. Largely, conditions will stay VFR, but it`s conceivable that ceilings lower to MVFR in some areas from the Cascades westward with partial obscuration of higher terrain. Starting tomorrow afternoon there could be wind shear at the coast through 2000 feet nearing 30 to 40 knots. This has been added to the OTH TAF, and this is expected to continue into Sunday morning. LLWS will build in more locations, especially the Cascades and east. -BR-y/Hermansen && .MARINE...Updated 845 PM PST Friday, February 21, 2025...An active weather pattern will cause hazardous conditions this weekend into next week. Increasing south winds and building seas with conditions hazardous to small craft will continue tonight. Winds increase to gales tomorrow into Sunday with very steep, hazardous seas, especially from around Cape Blanco northward. Another strong frontal system will move through Monday with another round of gales possible. Additionally, guidance shows a high west swell (14-17 ft at 12 -14 seconds) building into the waters Monday into early Tuesday, with seas possibly peaking in the 16 to 20 ft range Monday afternoon/evening. Steep to very steep seas persist into Tuesday, then things should calm down from Wednesday onward. -BR-y/Hermansen && PREV DISCUSSION... /Issued 216 PM PST Fri Feb 21 2025/ DISCUSSION... Plenty of high clouds on satellite as of this afternoon as some upper level energy moves through the region. We`are anticipating little to no precipitation from this wave as it runs through the Pacific Northwest. The leading edge of an atmospheric river(AR) will hit southern Oregon and northern California by mid day Saturday. This plume of warm moist air will raise snow levels up to 7000 feet by Saturday evening and bring widespread wetting rain to the region. Precipitation rates really pick up by Saturday evening into Sunday morning as model guidance is showing rain rates of about 1.5-2" over 6 hours around Curry County. Integrated water vapor transport(IVT) is also on the stronger side around 500 to 750 for about 24 hours. Ensemble situational awareness tools suggest these IVT values lie in the 98th percent for this time of year, which is notable and suggest a strong AR. The other thing that stands out is how much moisture is in the air. Precipitable water is anticipated to reach 1 inch by Saturday night. This would lie in the 99th percentile for this time of year based on sounding climatology for SPC and ensemble situation awareness tool. Our record values are right around 1.2 inches. Between Sunday into Monday, another upper level disturbance in this AR event will swing through region pushing the bulk of the precipitation farther north, although we`ll still see rain accumulate through Monday morning with a lighter rain continuing into Tuesday. The flooding risk is still expected to be minor/limited as this AR hits the region through Tuesday. Main stem rivers and streams will rise rapidly through Sunday, although none of the rivers are anticipated to reach action stage or minor flood. The one concern that we do have is snow melt east of the Cascades in south central Klamath and Lake Counties. That area got the brunt of snowfall from the event a few weeks ago. However, not much rain is anticipated to fall east of the Cascades. Plus, overnight lows will fall very close to freezing east of the Cascades, so the contribution of snowmelt overnight will be very limited. However, there have been events in the past of some small stream flooding east of the Cascades due to snow melt, so it`s just something to watch out for. Aside from flooding concerns, winds will be strong on Monday evening in the Shasta Valley. Models are anticipating a low to form off the British Columbia coast with southwest flow at 45 knots developing over southern oregon and northern California. Areas east of the Cascades will be breezy with the typical 45 mph south to southwest wind gusts around Summer Lake and other exposed locations. The GFS seems to be a little too strong with this low, but we anticipate some strong south winds in the Shasta Valley Monday. Tuesday evening will be the end of this AR event with high pressure building over the area. This quiet weather will persist into Wednesday with temperatures continuing to remain on the warmer side. Highs will be pushing the mid 60`s west of the Cascades with some upper 60`s in the river valleys closer to the coast. Temps will be a bit cooler east of the Cascades on Wednesday with highs in the mid 50`s. A low chance of rain returns on Thursday as an upper level wave quickly swings through the region. -Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 10 AM PST Sunday for PZZ356-376. Small Craft Advisory until 10 AM PST Saturday for PZZ350-370. Gale Warning from 10 AM Saturday to 10 AM PST Sunday for PZZ350- 370. && $$

372 FXUS66 KEKA 212246 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 246 PM PST Fri Feb 21 2025 .SYNOPSIS...Upper and mid-level clouds are filling in ahead of inclement weather with stratus returning to the coast. The chance for rain increases this weekend and continues into early next week. Gusty southerly winds expected along the North Coast and over the interior mountains this weekend and early next week. && .DISCUSSION...Despite a synoptic ridging pattern lasting through the next several days and into next week, a series of disturbances will incorporate subtropical moisture and inundate the area mostly to the north our CWA. More immediately, 500mb heights show the ridge flattening a bit Saturday, which will allow some of this precipitable water to train over Del Norte and Humboldt counties. Tonight there looks to be an initial phase of this series of pulses but the probabilities are negligible to none according to high res models yet CAMs show light showers tonight if any. This first slug of moisture will produce light precip locally as the majority of accumulation will be north of 43N, which will hit Oregon and Washington early Saturday morning with an IVT magnitude of around 750kg/m/s. The next frontal boundary will produce beneficial rain by the late afternoon into the early evening on Saturday. Expect mostly beneficial rainfall. Minor nuisance flooding is possible with the heavier rainfall Saturday night into early Sunday. Mudslides will also be possible in the steep terrain on highway 199 in Del Norte County Saturday night when the heaviest rain rates occur. Otherwise, expect mild temperatures with a chance for light rain for the remainder of the area during the weekend. Gusty winds will also occur with this stationary boundary and minor impacts are possible especially over the coastal headlands. A surface low is forecast to develop just outside 135W north of 40N on Monday and stronger wind gusts to 50 mph are possible for the coastal headlands and interior ridges as the pressure gradient tightens and a 925mb southerly 50kt+ speed max develops along the coast in advance of a frontal boundary. The exact timing remains uncertain, though the ECMWF has been clustering around Monday afternoon/evening with ensemble mean gusts near 50 mph for Pt St George and KCEC airport. Looking at the NBM, 90th percentile max gusts are on the order of 55 to 65 mph over the interior mountains of Del Norte with lower probabilities for gusts over 50 mph for the Humboldt interior mountains; Kneeland and Berry Summit. Wind this strong will make driving difficult and could knock down tree branches. Precip should start to end on Tue as broad upper ridging quickly springs back and holds into mid week (Wed). The ridge aloft with above normal 500mb heights will likely remain the dominant feature controlling NW California weather into late next week. Temperatures will likely remain above normal. /DB /EYS && .AVIATION...High level cloud cover has been increasing this afternoon across the north coast ahead of an approaching upper shortwave. VFR conditions have prevailed as a marine stratus deck has mostly remained offshore, but increasing onshore flow may produce scattered MVFR ceilings/mist this afternoon, especially at ACV. This initial shortwave will bring the potential for light rain showers overnight into early Saturday morning. Model reflectivity indicates the highest potential for scattered showers at CEC between 04-08Z, but any accumulation would be minimal (<.10 in). HREF probabilities are <30% for ceilings <2000 feet overnight, although brief periods MVFR ceilings are possible with these passing showers. Southerly winds will steadily increase Saturday ahead of a stronger frontal boundary. Heavy rainfall and gusty winds 25 to 35 mph are possible in northern Humboldt and Del Norte county late Saturday night into Sunday as this front moves onshore. && .MARINE...A mid-period westerly swell 9-11 feet at 15 seconds will build into the waters this evening. Light westerly breezes will turn southerly and increase overnight ahead of an approaching upper shortwave, elevating the sea state to advisory levels as significant wave heights surpass 10 feet. Near gale force gusts are possible in the northern waters late Saturday night into early Sunday morning as a fast-moving frontal boundary moves onshore. Responsive 7 to 9 foot wind waves will enhance already elevated seas through Sunday. An active upper trough pattern will sustain elevated southerlies through early next week; a stronger front is possible Monday afternoon with potential for gale force gusts coinciding with the arrival of a large, long period westerly swell. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement through late tonight for CAZ101-103- 104-109. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory from 3 AM Saturday to 3 PM PST Sunday for PZZ450. Small Craft Advisory from 3 AM to 3 PM PST Saturday for PZZ455. Small Craft Advisory from 9 PM this evening to 3 PM PST Sunday for PZZ470. Small Craft Advisory from 9 PM this evening to 3 PM PST Saturday for PZZ475. && $$ 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

236 FXUS66 KMTR 220542 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 942 PM PST Fri Feb 21 2025 ...New AVIATION, MARINE... .SYNOPSIS... Issued at 1137 AM PST Fri Feb 21 2025 Another dry day across the region. Chance for light rain in the North Bay late Saturday through Sunday, and again on Monday. Otherwise, the forecast remains dry with a warming trend through the next week. && .UPDATE... Issued at 844 PM PST Fri Feb 21 2025 Dry conditions continued throughout the day today from the high pressure system bringing us warmer temperatures. Some areas in our region, specifically inland valleys, reached temperatures of lower 70s while coastal ranges reached temperatures of lower 60s to even higher 50s. Tonight we should expect some cooler temperatures due to minimal sky coverage which will bring the North Bay area, specifically Napa, some foggy conditions late tonight into the early Saturday morning. Saturday we should see the fog dissipate with warm and dry conditions for some continued beautiful weather! SB && .SHORT TERM... (This afternoon through Saturday) Issued at 1137 AM PST Fri Feb 21 2025 Mostly clear skies prevail over the Bay Area and Central Coast, with a few cirrus clouds in the sky. Today should be a dry and clear day with high temperatures reaching the upper 60s to the lower 70s across the inland valleys, the lower to middle 60s along the Pacific coast and Bayshore, and the upper 50s to the lower 60s in the higher elevations. Winds will be light with a slight onshore breeze developing during the afternoon before light offshore and valley drainage flows resume overnight. Low temperatures on Saturday morning range from the upper 30s to lower 40s in the inland valleys, to the middle to upper 40s along the coasts and in the higher elevations. Saturday will be an equally dry day with a slight warming across the inland valleys of the South Bay and Central Coast, where highs will reach the lower to middle 70s, otherwise highs remain similar to today`s. && .LONG TERM... (Saturday through Thursday) Issued at 1137 AM PST Fri Feb 21 2025 The long term forecast has not changed appreciably since the last update. The previous long term discussion follows for reference: Upper level zonal flow through the weekend and into early next week due to additional shortwaves moving across the PacNW. This may bring a few light showers to far northern Sonoma and Napa counties Sunday into Monday, though if that were to happen rainfall amount generally appear to be negligible to perhaps a few couple hundredths of an inch. Otherwise, dry and warmer weather persists. Upper level ridging builds by midweek. Agree with the previous shift in that high temperatures will be worth watching out for given the proximity to the records. For now, kept the NBM forecast in, but should the trends continue to lean warmer we may need to bump the forecast up a few degrees. By late week or next weekend, guidance from ensemble and deterministic models shows a cut off low developing and tracking over CA. It`s too early to say where but it could bring a few showers to the region. && .AVIATION... (06Z TAFS) Issued at 942 PM PST Fri Feb 21 2025 VFR continues for all terminals. There is a chance for MVFR/IFR/LIFR conditions early Saturday morning for KSTS, KHAF and KSJC, but confidence is low. Some low stratus may develop near SF Bay terminals overnight with a slight chance that conditions become MVFR/IFR but models show agreement of VFR through the TAF period. Otherwise, light winds overnight with light to moderate onshore winds returning by Saturday afternoon. Vicinity of SFO...VFR through the TAF period. Onshore winds have remain breezy a bit longer than expected, but expect winds to diminish to light overnight and rebuild to breezy by Saturday afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. Winds build to moderate and turn to a S/SE direction overnight before returning to W/NW by Saturday morning. && .MARINE... (Tonight through next Thursday) Issued at 942 PM PST Fri Feb 21 2025 Seas and winds continue to remain relatively calm with conditions lasting into the early part of next week. A new, moderate northwesterly swell enters the waters by Tuesday of the upcoming week, causing seas to build up to 11-12 feet. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...DialH LONG TERM....KR AVIATION...SO MARINE...SO 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

332 FXUS66 KOTX 220553 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 953 PM PST Fri Feb 21 2025 .SYNOPSIS... Warmer temperatures and rain will arrive this weekend as high temperatures warm into the 40s and low 50s. Runoff from rain and melting snow will lead to increased flow and minor flooding across southeast Washington and the central and southern Idaho Panhandle. Another weather system Monday into Tuesday will bring more rain and stronger winds. && .DISCUSSION... Tonight thru Saturday: As a disturbance moves into and across Inland Northwest, snow levels will be low enough for light snow to mix in with developing rain across populated areas this evening into overnight. Snow levels will rise through Saturday morning so that most precipitation will be rain outside of the mountains. Areas of fog will again be a concern overnight in favored areas, though it`s not anticipated to be as wide-spread as last night. The highest precipitation totals with this first round of precipitation through Saturday will be across the Cascades, far eastern Washington, and north Idaho. /KD Saturday Night to Wednesday: Three systems will pass through the PacNW between Saturday Night and Tuesday, with warmer temperatures, wind, and precipitation. The first will arrive late Saturday, with a warm front lifting north across the Inland Northwest. Precipitation will mainly fall as rain at lower elevations and snow at higher altitudes, with the Cascades, eastern WA, and northern ID expecting the highest totals. Snow levels will rise throughout the night, with a wintery mix developing over the Methow Valley that could contain some pockets of freezing rain. A second wave will pass through Sunday, driven by a compact low- pressure system move through the region. Models show varying forecasts, but we have gone slightly on the higher side. Current forecast have 0.5 to 1.0 inches of rain for the lowlands and 1.5 to 2.5 inches for the higher mountain peaks. Winds will also increase as well, mainly over the Columbia Basin and Palouse, with gusts up to 30 mph. The combination of rain, rising temperatures and breezy winds will lead to rapid snowmelt across the lowlands where snow is present. This could cause localized flooding, particularly in urban areas with poor drainage and fields. Several creeks and river are expected to rise, reaching near action stage for areas from Palouse up to the Spokane area. A deeper low is expected to bring more preciptiation and possibly stronger winds to the region on Monday night into Tuesday. Winds this time will be strongest in the early morning, with gusts of 35 to 40 mph expected near the Columbia Basin and the Palouse. /KK Tuesday Night through Friday: Models are in good agreement of an upper level ridge building Wednesday. Thursday and Friday models start to diverge on a trough moving toward the west coast. 60% of the ensembles cut off the low off the southern CA coast. 40% show a faster weaker wave moving through the southwest US. Either way, it looks like the Pac NW will be under the influence of higher heights and drier conditions. Temperatures will remain above average for the end of February. The NBM is forecasting high temperatures above the 90th percentile. Have lowered our temps down several degrees closer to what the ensemble mean has. The tricky part is if fog or stratus forms after these wet weather systems move through with abundant low level moisture. If so, our daytime temps will be quite a bit cooler. If we clear out and see sunny skies, our temperatures will be warmer. For now, have highs in the mid 40s to mid 50s, and lows in the upper 20s to mid 30s. /Nisbet && .AVIATION... 06Z TAFS: As a storm system moves into the area with precipitation beginning around 08Z for many of the TAF sites, ceilings will lower into MVFR through the night. Every TAF site but KMWH will stay mostly at VFR/MVFR with lowered ceilings due to precipitation. KMWH looks to get down to IFR at some point through the evening due to localized rainfall and low stratus. KEAT is the only TAF site that has low enough temperatures to support a possible rain/snow mix. A second round of rain will move in close to the end of the TAF forecast period. There is the potential for KGEG-KSFF-KLWS to see wind shear values of 30 knots or more at 2000 feet Saturday evening. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate confidence in timing and location of upcoming precipitation, particularly with the second wave later in the TAF period. Moderate to high confidence of MVFR ceilings for all but KEAT through the night. Moderate to low confidence of wind shear values being greater than 30 knots difference at KGEG-KSFF-KLWS for Saturday evening. /AS ----------------------- 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 35 43 40 49 40 50 / 50 50 100 90 80 50 Coeur d`Alene 35 43 39 47 38 48 / 60 60 100 100 90 50 Pullman 34 42 38 45 39 48 / 40 40 100 100 90 50 Lewiston 37 47 41 52 42 54 / 20 20 90 100 90 40 Colville 33 41 38 46 34 47 / 70 40 100 80 80 40 Sandpoint 35 41 39 44 38 46 / 80 80 100 100 90 60 Kellogg 35 42 41 45 40 46 / 50 70 100 100 90 60 Moses Lake 32 47 39 55 38 52 / 30 20 70 70 40 40 Wenatchee 33 41 39 48 38 47 / 40 30 70 70 50 50 Omak 34 41 36 46 35 47 / 50 40 90 70 60 40 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

046 FXUS66 KPDT 220630 CCA AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1030 PM PST Fri Feb 21 2025 .UPDATED AVIATION DISCUSSION... .AVIATION...06Z TAFs...KPSC is currently in VFR before briefly deteriorating to IFR due to low clouds and mist until tomorrow morning. And with the system arriving, fog may develop tonight around KDLS as well (<20% chance). KPDT/KALW/KPSC may receive lingering rain later tonight, but chances are low (20-40% chance). Otherwise, most sites (KDLS/KPDT/KRDM/KBDN/KYKM/KALW) will be in VFR throughout the TAF period. Widespread showers is forecasted for KDLS/KPDT/KRDM/KBDN/KYKM tomorrow night. Gusty winds will develop late morning to afternoon as high as 20-30 kts for sites KRDM/KBDN/KALW. Feaster/97 && .PREV DISCUSSION... /issued 350 PM PST Fri Feb 21 2025/ SHORT TERM...Today through Sunday night... Key Messages: 1. Light mountain snow and Basin showers tonight. 2. Widespread rain returns Saturday afternoon through Sunday. 3. Windy conditions Saturday evening through Sunday. 4. Warming temperatures through the weekend. Current radar and visible satellite imagery showing light returns extending across the Basin under partly to mostly cloudy skies. This is in response to an upper level shortwave that is suppressing the upper level ridge that brought us mostly clear skies Thursday and through the early part of today. The light returns are indicative of elevated moisture that is currently not reaching the ground surface due to the lingering dry air at lower levels of the atmosphere. This air will slowly moisten through the evening, but is only expected to result in light accumulations of a trace to 0.01" across the Lower Columbia Basin of Washington. Confidence in these rain amounts is high (80%) as the NBM suggests only a 10-30% chance of measurable rainfall (0.01" or more) this evening. Higher elevations above 4000 feet across the Cascade and northern Blue Mountains will receive 0.5-1.5 inches of snow, with elevations between 3000 and 4000 feet receiving primarily rain with 0.05-0.15" likely. Tonight`s shortwave will allow for southwest flow aloft to set up ahead of the next shortwave that will pass through the area Saturday afternoon, accompanied with a weak Atmospheric River supplying the moisture. This will increase snow levels into the 7500-8500 foot range by Saturday afternoon, extending through Sunday. Showers will begin along the Washington Cascades by 4 PM before extending into the Basin by 8 PM and the northern Blue Mountains by 10 PM. Precipitation will then enhance overnight and through Sunday evening as the Atmospheric River dissipates shortly after 4 PM Sunday. Highest rain amounts are expected to occur across the Cascades with 1 to 2 inches of rainfall Saturday with an additional 1.5 to 2.5 inches Sunday for elevations above 4000 feet. Confidence in these rain amounts is high (80-90%) as the NBM suggests an 85-95% chance of 1 inch of rain or more for both Saturday and Sunday. Rain amounts along the northern Blue Mountains will be between 0.50 to 1.0 inch Saturday with an additional 1 to 2 inches Sunday primarily above 3500 feet. Confidence in these rain amounts is moderate to high (60-80%) as the NBM advertises a 50-60% chance of 0.75" of rain or more on Saturday and a 70-80% chance of 1 inch or more on Sunday. The Blue Mountain foothills should receive 0.05 to 0.15" Saturday and 0.25 to 0.60" Sunday, with the NBM showing a 40-60% chance of 0.10" or greater Saturday and a 50-80% chance of 0.40" or greater Sunday. Lower elevations of the Basin is expected to receive 0.01-0.10" Saturday and 0.10-0.20" on Sunday, with the NBM showing a 35-55% chance of 0.05" or more Saturday and a 50-75% chance of 0.15" or more on Sunday. The shortwave Saturday will also develop a pressure gradient along the Blue Mountains to allow windy conditions across the Grande Ronde Valley Saturday evening, extending along the Blue Mountains and foothills Saturday night into Sunday morning. Gusts of 40-50 mph out of the south look possible (60-70% confidence) as the GFS, NAM, and SREF highlight a pressure gradient of 6-8 mph between Baker City (KBKE) and Meacham (KMEH) and a 10-12 mb gradient between Ontario (KONO) and Meacham (KMEH). Further confidence is gleaned from the NBM, which suggests a 55-75% chance of advisory level wind gusts (45 mph or greater) over the Grande Ronde Valley Saturday evening through Sunday morning. The pressure gradient along the Blue Mountains will also lead to downsloping winds along the Blue Mountain foothills, as the GFS, NAM, and SREF suggest a pressure gradient of 4-7 mb between Pendleton (KPDT) and Meacham (KMEH). The GFS is the only guidance hinting at a gradient of above 5 mb, with the NBM indicating a 25-55% chance of advisory level wind gusts (45 mph or greater). Thus, further analysis is necessary as confidence in advisory-level winds is currently lacking (below 60%) for both regions. Winds will slacken through Sunday morning, but will briefly increase late Sunday evening. Southwest flow aloft will also lead to warming temperatures over the weekend, with high temperatures breaking into the mid-to upper 50s Saturday and low to mid-60s on Sunday across lower elevations of the Columbia Basin and Blue Mountain foothills. These temperatures are 10 to 15 degrees above normal. Confidence in these high temperatures is high (80-90%) as the NBM suggests a 50-65% chance of highs reaching 60 degrees or above on Saturday over lower elevations of the Basin, and a 60-80% chance on Sunday. 75 LONG TERM...Monday through Friday... Bottom Line Up Front 1) Moderate mountain rain/snow, light lowland rain to start 2) Warmer and drier conditions return by midweek 3) Hydrological concerns from Mondays system Monday into Tuesday night, models show yet another wet shortwave system making its way briefly across the region exiting by Tuesday night. The 48-hr raw ensemble probabilities ending Tuesday for precipitation accumulations for 2 inches or greater, show probabilities are between 80-90% along the Cascade crests, with less than 15-25% along the crests of the Northern Blues. Lower elevations show there is generally a 40-70% chance of 0.25 inches of rain across central & north central OR, the Yakima/Kittitas/Grande Ronde valleys, and along the northern Blue Mountain Foothills. Snow levels will be relatively high to begin with then steadily decrease to near 5500 feet. There is snow expected to fall above 5500 feet both Monday night through Tuesday night. By Tuesday night models show the leading edge of an upper level ridge making its way back over the region. Clusters show the models are struggling with the amplitude and timing of the ridge. Even with the variances, models show the region to be under dry conditions with precipitation returning to the Cascades while the remainder of the region stays dry through Friday with precipitation backing off the Cascades again. The southwesterly flow associated with these upper level shortwaves as well as the surface warm fronts associated with them will bring warmer temperatures across the region. Comparing the currently forecasted temperatures against the climate data temperatures for this time of year, these temperatures are anywhere from 5 to 10 degrees above normal for the lower and mid elevations and 2 to 5 degrees above normal for the higher terrains. By the end of the period, the entire region will be 5 to 10 degrees above climatological normal with a few isolated areas in central OR being nearly 15 degrees above. EFI is continuing to show temperatures are decently above normal for this time in the season with temperatures averaging in the upper 50s to low 60s in lower elevations, low to mid 50s along the mid elevations and in the upper 30 to mid 40s through the higher terrains on Monday. After Monday temperatures are still averaging above normal with temperatures in the 50s along the lower terrains, high 40s to low 50s along the mid elevations and mid 30s to low 40s for the higher terrains. Confidence is high (<85%) with temperatures that are forecasted for the long term. Lastly and most importantly, there are some hydrological concerns that are popping up from all the warm temperatures and precipitation. Rivers through the Yakima, Naches, Klickitat, Walla Walla and the lower Yakima River Basins will see rises in the rivers within the Naches at Cliffdell forecasted to break above bankfull by Monday with probabilities of 10-25%, Walla Walla River near Touchet with probabilities of 25-75% breaching action stage and Klickitat River near Pitt 10-25% reaching action stage as well. A hydrologic outlook has been issued and we will continue to closely monitor the river forecasts and work with the river centers as the day draws closer. In the meantime, be prepared and continue to remain vigilant and check the website for updated information regarding the rivers. Bennese/90 && .PRELIMINARY POINT TEMPS/POPS... PDT 34 59 45 61 / 20 30 80 90 ALW 36 54 45 57 / 30 40 90 90 PSC 35 58 46 63 / 30 40 70 80 YKM 32 49 40 58 / 30 20 50 80 HRI 33 59 46 64 / 20 30 60 80 ELN 32 46 37 53 / 40 30 60 80 RDM 35 59 45 60 / 20 10 40 80 LGD 33 45 37 47 / 20 30 80 100 GCD 33 52 40 52 / 20 30 70 90 DLS 38 54 46 60 / 20 30 80 90 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...75 LONG TERM....90 AVIATION...97

180 FXUS65 KREV 212144 AFDREV Area Forecast Discussion National Weather Service Reno NV 144 PM PST Fri Feb 21 2025 .SYNOPSIS... * A warming trend will result in spring-like temperatures this weekend into early next week. * A pair of weak storms will being increased winds and light showers to northeast California and northwest Nevada Sunday and Monday. * No significant winter storms expected through the end of February with a more active weather pattern possible in early March. && .DISCUSSION... Today`s abundant sunshine and highs in the upper 40s and 50s has been brought to you by high pressure aloft, which is keeping the storm track well to our north. We`ll get our first taste of spring this weekend as temperatures warm to 10-15 degrees above normal, making it feel more like April than late February. Spring-like weather continues into early next week with Monday serving as our warmest day when some Basin and Range communities (e.g., Fallon, Hawthorne, Yerington) see their first 70F reading of the year. There is even 10% chance that Reno also breaks the 70F mark on Monday. The remainder of February will be predominately dry as the aforementioned high pressure area prevents winter storms from impacting the Sierra and western Nevada. However, a couple weak storms will transit close enough to the region to support periods of light showers and gusty winds late Saturday through Monday. The first storm brushes by late Saturday into early Sunday, bringing light showers from Lassen and E Plumas counties to far NW Nevada. A few showers may be able to sneak into the Tahoe Basin but odds are low (10-20%). The second storm passes by late Monday, increasing shower chances for a similar area. Little to no rain and snow accumulation is expected between both of these systems. Winds become breezy on Sunday with gusty winds along the Sierra crest, then will peak on Monday as gusty winds become more widespread. Blended guidance gives most western Nevada locales a 30- 50% chance of wind gusts reaching 40 mph or greater Monday afternoon. Be prepared for bumpy flights into and out of regional airports, choppy lake waters, and difficult driving conditions for high-profile vehicles. After Monday, lighter winds prevail with dry weather and unseasonable warmth, although a more active weather pattern may develop during the first week of March. -Salas && .AVIATION... Widespread VFR conditions with light breezes will prevail through the weekend. Periods of mountain wave turbulence and LLWS will be possible Saturday night through Monday for KTRK/KTVL and Sierra Front terminals as FL100 winds strengthen to 30-50 kts. Mountain obscuration will also be possible during this same timeframe with a 10-20% chance of showers at KTRK/KTVL. -Salas && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

956 FXUS66 KSTO 212126 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 126 PM PST Fri Feb 21 2025 .SYNOPSIS... Weak system brings light showers and breezy southerly winds to the Sacramento Valley, foothills and mountains Sunday and Monday. Dry weather and above-normal temperatures then prevail next week. && .DISCUSSION... Current GOES-West visible satellite imagery shows mostly clear skies across interior northern California early on this Friday afternoon. The north to east winds continue to decrease and lighter winds are currently being observed, valid at 130 PM PST. Temperatures are currently in the 60s to near 70 in the Valley and lower foothills, and in the 40s to 60s in the upper foothills mountains. Dry and warming weather will continue today and Saturday as upper level ridging continues to develop over the region. A weak weather system passing over the Pacific Northwest will bring a few showers to the Sacramento Valley, foothills and mountains, mainly on Sunday, with some lingering showers over Shasta County on Monday. Latest guidance from WPC has trended slightly higher and suggests total precipitation amounts of a few hundredths of an inch to a quarter of an inch over much of the aforementioned areas, with higher amounts of 0.25 to 1.5 inches in Shasta County. Slick road conditions will be possible at times, mainly for areas north of Interstate 80. Some locally breezy southerly winds will accompany this system on Monday with some gusts of 20 to 30 mph, mainly in the northern/central Sacramento Valley, adjacent foothills and Sierra Crest. && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Cluster analysis and ensemble guidance continue to support warm and dry conditions next week under upper level ridging. Daytime high temperatures will be trending above normal for late February / early March climatology, in the 60s to 70s in the Valley and foothills and 50s to 60s in the mountains. The NBM shows a 55 to 85 percent probability of high temperatures exceeding 70 degrees F throughout the lower elevations over the extended forecast period. There is also a 20 to 40 percent probability of temperatures exceeding 80 degrees F mid to late next week across portions of the northern/central Sacramento Valley. Light winds are generally expected with the exception of occasional periods of breezy north to east/downslope winds at times. && .AVIATION... VFR conditions are expected over the next 24 hours across interior NorCal, except for a brief period of MVFR conditions across portions of the northern San Joaquin Valley due to BR 13-17z Saturday. Winds will remain under 12 kts in the Valley. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

186 FXUS65 KMSO 212015 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 115 PM MST Fri Feb 21 2025 .DISCUSSION... KEY MESSAGES: - Increased snowmelt and runoff Saturday into Monday, bringing the risk of minor flooding to low-lying and poor drainage areas and to small streams and creeks from potential ice jam releases. - Widespread rain and high elevation mountain snow, Sunday into Monday. - Areas of freezing rain Saturday morning, becoming more widespread Sunday morning across western Montana with cold subsurface ground temperatures in place. GOES Satellite imagery shows a ridge of high pressure building over the Northern Rockies this afternoon, with areas of sunshine allowing for temperatures to climb well above freezing across valley areas. Our next Pacific disturbance is beginning to push onshore in the Pacific Northwest, with moisture arriving late tonight into Saturday morning along the ID-MT border and in northwest Montana. Rising snow levels and mild temperatures will focus snow accumulations over the higher terrain, with minor accumulations of a trace to up to 1 inch, focused across Lincoln and Flathead Counties. Pockets of freezing rain are also a concern into Saturday morning across northwest Montana given cold sub- surface ground temperatures in place. A long duration (~48 hour) atmospheric river event remains on track to impact the Northern Rockies Sunday into Monday, delivering widespread precipitation and pushing snow levels above 6,000 feet. Warm, wet, and breezy conditions in the lower elevations will set the stage for rapid snowmelt, leading to runoff concerns and introducing the risk for minor flooding in low-lying and poor drainage areas across western Montana and north-central Idaho. Furthermore, the rapid thaw of small streams and creeks may lead to ice jam releases. Given rising snow levels and widespread precipitation, an elevated risk also exists for rock slides, particularly across north-central Idaho and along the ID- MT border, where confidence is high (80% probability) for widespread precipitation totals exceeding one inch. Higher peaks across the Northern Bitterroot, Cabinet, and Clearwater Mountains will see the highest precipitation totals of 2-4 inches. Finally, given the intensity of this system and changes to the snowpack, those planning winter recreation activities are encouraged to monitor avalanche forecasts at avalanche.org Another concern is the risk of icy conditions, particularly overnight Saturday night into Sunday morning. Although air temperatures may rise above freezing, many western Montana valleys still have subsurface temperatures below freezing. This could result in rain freezing on contact, creating hazardous conditions, especially on secondary roads with lingering snow cover. Travelers should be prepared for slick spots, particularly on untreated surfaces. Winter weather advisories have been issued across northwest Montana where our confidence is currently the highest for more widespread impacts to occur. The next Pacific disturbance is expected late Monday night into Tuesday. Snow levels will initially start around 5000 feet, but will drop once again on Tuesday morning as a cold front moves through the region. By this point, the main moisture source will be cut off, but lingering snow showers will likely exist. In fact, some forecast models are showing a pattern that could be conducive for snow bands Tuesday morning. && .AVIATION...Satellite imagery and webcams show northwest Montana terrain still obscured by clouds, while much of the region enjoys mostly sunny skies with increasing high-level cloud cover. However, moisture is on the rise from the southwest, and model cross-sections suggest clouds will thicken and lower tonight, particularly over north-central Idaho and northwest Montana. As moisture builds, high resolution models indicate showers developing in these areas by Saturday morning. By Sunday, an atmospheric river will bring rising snow levels and widespread valley rain, leading to a wet and active weather pattern. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Flood Watch from Saturday afternoon through Monday afternoon for Bitterroot/Sapphire Mountains...Butte/Blackfoot Region... Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower Clark Fork Region...Missoula/Bitterroot Valleys... Potomac/Seeley Lake Region...West Glacier Region. Winter Weather Advisory from 11 PM Saturday to 8 AM MST Sunday for Flathead/Mission Valleys...Kootenai/Cabinet Region... West Glacier Region. ID...Flood Watch from Saturday afternoon through Monday afternoon for Lower Hells Canyon/Salmon River Region...Northern Clearwater Mountains...Orofino/Grangeville Region... Southern Clearwater Mountains. && $$

053 FXUS65 KBOI 220327 AFDBOI Area Forecast Discussion National Weather Service Boise ID 827 PM MST Fri Feb 21 2025 .DISCUSSION...Mid and high clouds will continue to move in from the west overnight, with light showers spreading across the higher terrain in the north. This initial weak wave will move east out of the area Saturday afternoon, only to be followed by a stronger and quite wet system Saturday night into Sunday. Latest guidance shows no significant trends, and no update is needed at this time. See previous discussion (below) for additional details. && .AVIATION...Mostly VFR. Isolated MVFR/IFR in valley fog and/or low stratus mainly near KMYL, KONO, and KBKE late tonight. Surface winds: variable 5 kt or less except NE-SE 5-15 kt near KJER/KMUO. Winds aloft at 10kft MSL: W 10-20 kt, increasing about 5 kt Saturday. KBOI...VFR. Possible MVFR ceilings Sat 12Z-18Z (30% chance). Surface winds: SE 4-8 kt. Sunday Outlook...All flight categories expected as widespread precip continues after moving in Saturday night. Snow levels generally 6-7000` MSL. Mountains obscured. Surface winds: SE-SW 5-15 kt with gusts 20-30 kt. && .PREV DISCUSSION... SHORT TERM...Tonight through Sunday night...A weak upper wave will track across the region late tonight and Saturday. Outside of a low chance of showers across e-central Oregon and w-central Idaho, it most areas remain dry through the day. Any areas that pick up light snow will see less than a 1/2 inch through midday Saturday. A much wetter pattern will unfold late Saturday night into Sunday as an atmospheric river pushes into the Pac NW. Modeled precipitable water data show this plume (1-1.5" values) to have a sub-tropical connection west of the Date Line. While the core of strongest winds aloft are forecast to remain just north and west of the region, there will be plenty of moisture transport in from the coast to generate rain and high elevation snow. Precipitable water values reach the 98%+ with W-SW winds at ~10kft MSL reaching 30-50 mph. This will favor a period of continuous moderate to locally heavy precipitation on Sunday, especially across e-central Oregon, and the w-central ID and Boise mtns. In these areas snow levels will start between 3500-4500 feet MSL Saturday night, allowing for minor accumulation of wet snow. The incoming Pacific air mass will quickly raise snow levels to between 6-8kft across the region on Sunday, bringing a rain/snow mix or changeover to rain except across the highest elevations. Total liquid amounts will reach 0.75-1.25" across the mountains with locally higher amounts of 1.5-1.75" translating to a wet 6-12" of snow above 7kft MSL through Sunday night. At lower elevations, rain totals of 0.1-0.3" are forecast through Sunday night. Valleys and mtn valleys will see breezy winds while higher mountains, tapping into the flow aloft, realize the strongest winds with gusts of 30-40 mph. Temperatures will be near normal Saturday and Sunday. At this point we expect much of the mtn snowpack to be able to absorb the rain with minimal snowmelt. Some runoff is expected and with frozen ground this could lead to water ponding in low lying areas where drainage is limited. There is of some question on how the lower elevation snowpack will respond but we do expect rain/melt/higher elevation runoff to impact river flow. While all rivers are showing forecast rises, the Weiser, Malheur, Payette and Donner und Blitzen are a few that we`re keeping an eye on as hydrologic forecasts show a more notable response in these rivers by Monday. Otherwise expect to see smaller streams running near bankfull early next week. LONG TERM...Monday through Friday...The atmospheric river will weaken on Monday, as zonal upper level low begins to strengthen over the region. Snow and rain showers will continue over the mountains through Tuesday, with snow levels rising to around 6500-7500 feet by Monday afternoon. Monday will be the warmest day of the long term period, with lower elevation highs in the upper 50s to low 60s (Boise has a 20% chance of exceeding 60F!), and mountain daytime highs in the mid 30s to mid 40s. Large precipitation totals from the Sunday-Monday atmospheric river event will occur, with valleys seeing anywhere from 0.25-0.50 inches of rain and mountains 1.00- 1.25 inches of rain for the 48 hour totals. Snow amounts above 6500- 7500 feet will be low, with most populated locations/roadways seeing anywhere from 1-3 inches, with high summits seeing up to 12-16 inches. A weak low will skirt to north of us on Tuesday, dropping temperatures by 3-6 degrees and decreasing snow levels to 4500-5500 feet. Lingering snow showers will persist in the West Central Mountains on Tuesday, but a deep upper level ridge of high pressure will begin to build across the Western US by late Tuesday. This will keep our temperatures above normal with dry conditions through Friday. Excellent model agreement remains through the long term period in the evolution of the ridge, so forecast confidence in dry and warm conditions is high. AVIATION...Widespread MVFR and local IFR conditions in rain and snow. Mountains obscured. Precipitation diminishing from west to east overnight. Snow levels 3500-5500 feet MSL, lowering to 3000- 4000 feet MST behind a cold front tonight. Surface winds: generally E to S 5-15 kt with gusts to 25 kt, shifting to the W-NW tonight. Winds aloft at 10kft MSL: W-SW 20-35 kt shifting to the N-NW tonight. KBOI...VFR with occasional MVFR conditions in rain. Rain may mix with snow this evening before ending by Thu/06Z. Surface winds: SE 5-15 kt, gusting to around 20 kt, shifting to the NW less than 10 kt after Thu/02Z. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...SP AVIATION.....SP SHORT TERM...DG LONG TERM....SA

564 FXUS65 KLKN 212006 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1206 PM PST Fri Feb 21 2025 .SYNOPSIS...Mainly quiet conditions with gradually warming temperatures through the weekend. On Sunday, light showers are possible along the ID/NV border. Otherwise, warmer conditions at all locations with near record temperatures possible this weekend over central Nevada. && .SHORT TERM...Tonight through Saturday night. Skies are mostly sunny this afternoon with mainly high clouds moving over northern and central Nevada. This is due to high pressure over the area. Expect quiet weather conditions and gradually warming temperatures through the short term. For tonight, skies will be mostly clear with overnight lows in the teens and 20s. Look for mostly sunny skies tomorrow with highs in the 50s, with near 60 degrees in some portions across central Nevada. Winds will be light. Here are some probabilities of high temperatures greater than 55 degrees for select locations across northern and central Nevada for Saturday afternoon: Austin - 30% Battle Mountain - 95% Carlin - 10% Elko - 3% Ely - 100% Eureka - 90% Jackpot - 0% Jarbidge - 0% Owyhee - 3% Ruth - 0% Spring Creek - 0% Tonopah - 98% Wells - 0% West Wendover 0% Wildhorse Res - 0% Winnemucca - 96% By Saturday night, the upper ridge will be suppressed southward, with some mid-level moisture moving into far northern Nevada, near the border with Idaho. This could bring isolated showers to portions of northern Elko and Humboldt counties. Overnight lows will be in the 20s and 30s. Winds will remain light. .LONG TERM...Sunday through next Friday A combination of zonal and ridged upper level flow will dominate the pattern through at least Friday, allowing temperatures to climb. Near record highs will be present across the forecast area, and while no broken records are currently forecast it would only take a few extra degrees at the right time to change that. Tuesday sees a shortwave disturbance moving along the ridge that drops temperatures slightly along the Oregon/Idaho border and at high elevations in northeast Nevada, but they rebound by Friday. Some minimal precipitation is possible early in the week but clears out by Tuesday, leaving the rest of the week dry. && .AVIATION...Quiet and calm. Ceilings will be significantly above 3000 feet at all locations with winds remaining below ten knots and mainly terrain influenced. VFR at all sites through the Saturday afternoon. && .LKN Watches/Warnings/Advisories... None. && $$ 86/94/94