081 FXUS66 KSEW 210412 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 812 PM PST Mon Jan 20 2025 .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 /TONIGHT THROUGH THURSDAY/...Models have remained virtually unchanged in regards to the short term forecast. An upper-ridge is centering over the PNW as its axis cuts precisely over the Olympic Peninsula. We`ll remain dry and cool tonight with high pressure at the surface. Mid to high level cloud coverage will stream overhead, keeping those overnight lows relatively (much emphasis on "relatively") warmer than seen previously. Nevertheless, values are forecast to fall into the mid to upper 20s. Coastal spots will be the warmest with values in the lower to mid 30s. Transient shortwave trough briefly overhead during the first half of the day on Tuesday. This feature will be followed by the redevelopment of more upper-ridging by Tuesday night into Wednesday. It`ll last through most of the remaining short term period. However, conditions are beginning to converge on another incoming shortwave trough but this time is accompanied by moisture. Deterministic guidance still has some disagreement in exact timing but the NBM has widespread PoPs painted across W WA by Thursday night. Below normal temperatures remain favorable with highs in the lower to mid 40s and lows in the mid 20s to lower 30s. .LONG TERM /FRIDAY THROUGH MONDAY/...Guidance agrees on the development of an amplified ridge over the weekend and into early next week. A rex block pattern looks to set up shop around this time so a period of sustained ridging could be at play. To reflect this, the Climate Prediction Center has temperatures and precipitation trending below normal throughout the next 6 to 10 days. McMillian && .AVIATION...The upper ridge over Western Washington will flatten tonight as a weak trough aloft moves through the area. Westerly flow tonight will then become more northwesterly on Tuesday afternoon as the ridge builds back offshore. VFR cigs with high clouds through this evening. Localized LIFR cigs and vsbys will be possible again later tonight into Tuesday morning, mostly from Olympia southward and along spots of south Puget Sound. Otherwise, VFR cigs with high clouds at times and increasing mid to high clouds along the Olympic Peninsula on Tuesday. Light winds will continue through Tuesday. KSEA...VFR conditions with high clouds into tonight. Low clouds and LIFR vsbys are expected to remain south of the terminal on Tuesday morning, with only a 10% chance of LIFR. Otherwise, VFR on Tuesday with high clouds at times. Light north winds of 3 to 7 kts are expected through this evening, with winds becoming light S/SE tonight into Tuesday. JD && .MARINE...High pressure will remain over the waters into this evening. A weak system will move by to the north into Tuesday, but no impact is expected for the waters. High pressure will then build back into the waters Tuesday night and remain through Thursday morning. A weakening front will move southwards through the area Thursday night into Friday for increasing northerly winds, especially for the Coastal Waters. Small Craft Advisory winds will be possible during this period for at least the Coastal Waters. Increasing Fraser Outflow is expected later early Saturday, with more north to northeasterly winds over the weekend. Seas will be 4 to 7 feet through Tuesday before subsiding to 3 to 5 feet on Wednesday. Seas will then build with the next front Thursday night into Friday to 9 to 13 feet. JD && .HYDROLOGY...No river flooding in the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

757 FXUS66 KPQR 210523 AFDPQR Area Forecast Discussion National Weather Service Portland OR 923 PM PST Mon Jan 20 2025 Updated aviation discussion. .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...Monday afternoon 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 IFR/LIFR visibilities around 14-20Z 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 northerly winds in the central/southern Willamette Valley. Winds will be generally less than 5 kts except for through the Columbia River Gorge where winds will continue to decrease through 12Z. Cold overnight temperatures and clear skies continue, supporting frosty conditions on the ground and freezing fog if fog develops. PDX AND APPROACHES...Clear skies and VFR conditions expected through the TAF period. Will see easterly winds less than 5 kts except for around KTTD where could see winds with occasional gusts up to 20-25 kts through 08Z Tuesday. ~Hall/HEC && .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

922 FXUS66 KMFR 210526 AFDMFR Area Forecast Discussion National Weather Service Medford OR 926 PM PST Mon Jan 20 2025 ...Updated AVIATION discussion for 06Z TAFs... .DISCUSSION... Clear skies have developed this afternoon as temperatures have shot through the 30`s and are currently in the upper 40`s in most of the valleys west of the Cascades. Closer to the coast, highs are in the upper 50`s with some light north east to east flow at 4500 feet. Some higher clouds are starting to shuffle into the forecast area, and they should become more widespread later tonight based on cloud cover from the HREF model. By later tonight, we`ll likely see more valley stratus and freezing fog in the valleys. The MET and MAV guidance is predicting fog, and low temperatures will be well below freezing in many of the valleys tonight. The high clouds could throw a wrench in things, although we`re thinking that the dry layer and inversion strength should usher in plenty of fog. By Tuesday, mid and low level flow becomes onshore with light westerly winds. No big pattern changes as high pressure remains in control, although the different wind direction could push some lower stratus into the coast Tuesday afternoon and evening. High pressure will strengthen into Wednesday with the 500 mb ridge centered right over southern Oregon and northern California. The end result should be plenty of freezing fog, some of it being very thick and under 1/4 a mile given the strength of surface high. Finally, the weather will change around Thursday when the majority of models are predicting an upper level trough and cold front to push through the forecast area. The end result will be a 30 to 40% chance of precipitation across the majority of the forecast area with drier probabilities down to 0 to 20 percent farther south. Precipitation will likely be light as none of the ensemble members are predicting more than 0.3 inches through this Friday event. High pressure will settle back in this weekend. -Smith && .AVIATION...21/06Z TAFS...VFR levels continue across northern California and southern Oregon this evening. Guidance still shows slight chances of fog developing in the Umpqua Valley tonight, although those outcomes are disorganized and do not communicate dense, persistent fog. Development of patchy fog is not impossible in the Rogue Valley, but drier air limits those chances enough that fog is not included for Medford. Other areas look to remain at VFR through this TAF period. -TAD && .MARINE...Updated 930 PM Monday, January 20, 2025...Below advisory conditions present tonight look to continue into Tuesday 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. There`s good agreement for moderate to strong north winds later in the week with a strong thermal trough developing along the coast. Winds are likely to reach low end gales with steep to very steep seas. -Petrucelli && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 10 AM PST Tuesday for ORZ021- 023>026-029>031. Beach Hazards Statement until 4 PM PST this afternoon for ORZ021- 022. CA...None. PACIFIC COASTAL WATERS...Beach Hazards Statement until 4 PM PST this afternoon for PZZ350-356. && $$

367 FXUS66 KEKA 202314 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 314 PM PST Mon Jan 20 2025 .SYNOPSIS...Another frigid night is expected under a dry airmass with light or calm winds in the valleys. Dry weather and chilly mornings will continue Wednesday and Thursday. Some rain or snow showers are possible with a cold upper level trough Friday into Saturday. Blustery northerly winds will develop on Friday and continue into the weekend. Colder weather for the weekend. && .DISCUSSION...Temperatures bottomed out in the lower to mid 30`s in coastal areas and adjacent river valley early this morning. Low dewpoints tonight under an unseasonably dry air mass will allow temperatures to plummet this evening and overnight where winds remain light or calm. Trended low temperatures up some per the NBM and MOS guidance, however there may be mixed results. Some sites may decrease a few degrees with less valley fog while others increase due to warmer air aloft mixing down. Mostly thin high cirrus clouds may also factor in late tonight. A cold weather advisory has been issued with apparent temperatures expected in the upper 20`s. It will not take very much wind for it to feel colder than 30F. Otherwise, a wind advisory remains in effect for Lake County where ridge level gusts up to 50 mph are expected. Not confident about impacts for these remote ridge tops. Most population centers and travel corridors have been sufficiently windy with gusts from 20 to 35 mph to warrant continuation of the advisory. There was one report from a CWOP at Lake level with a max gust report of 54 mph early in this morning. 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. ECMWF EFI is already signaling the potential for strong north winds on Friday behind cold frontal passages, followed by robust NE or N winds over the weekend. Ensemble means are on the order of 25-30 mph gusts for the coastal land areas, with perhaps higher gusts for the headlands. Now the ridges and venturi effect sites will have stronger gusts to 50 mph or more based on the NBM 75-90th percentiles, especially in the King Range and eventually over the ridges and channeled terrain of Lake County. 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 a cold core trough sliding in from the eastern side with increasing magnitude. Therefore confidence is high for a dry forecast heading into Thursday. With the aforementioned trough comes a bit of precipitation potential. Latest WPC guidance has very little to only a few hundredths over the higher terrain. Even the deterministic and ensemble means are drier. It is too early to remove all precip chances as a few cluster means indicate a low end chance the cold core possibly digging offshore before swinging inland. This over-water trajectory could definitely be better for precip production vs what most cluster means indicate which is a dry overland trajectory. Right now the main impacts from the cold surge will be strong and blustery northerly and northeasterly winds and cold temperatueres. NAEFS indicate a 1 day every 2-5 years for 850mb temperatures of -2C to -4C, while the ECMMWF EFI is showing pockts of -0.5 to -0.7 with no shift of tails, There is potential for an unseasonably cold air outbreak filtering into NW Cal, however right now the signal is not decisive from any of these tools. Key message right now is cold and blustery. DB && .AVIATION...VFR and light winds continue into Tuesday. Some patchy valley fog is possible early Tuesday morning, although it is unclear if this will affect any terminals, and should any form it will mix out by late morning. && .MARINE...Winds will continue to diminish this afternoon and evening. Tonight the wind turn southerly around 5 to 10 kt and this continues through Tuesday. Seas remain calm, with buoys primarily picking up a swell of 7 ft at 16 seconds 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 model agreement that the northerly winds will start to increase again, reaching around 15 to 20 kt by the afternoon in the outer waters. 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 forecast Friday and Saturday. The global ensemble means 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 && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Beach Hazards Statement until 4 PM PST this afternoon for CAZ101-103-104-109. Cold Weather Advisory from 1 AM to 9 AM PST Tuesday for CAZ103-104-109-112-113-115. 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

468 FXUS66 KMTR 210432 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 832 PM PST Mon Jan 20 2025 ...New AVIATION, MARINE... .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. && .UPDATE... Issued at 815 PM PST Mon Jan 20 2025 First and foremost - change up to the ongoing headlines. The Wind Advisory for the North East Bay was cancelled early. The offshore gradient peaked earlier today and is currently on the downward trend. Winds are still breezy to gusty with 30-40 mph still being observed of the higher terrain, but not strong enough for the advisory. Given the offshore flow this afternoon temperatures rose to above seasonal averages in a few spots. What a rebound from Sunday to Monday for max temps. Sonoma County Airport did set an un- official record high of 70 deg. The official climate site in Santa Rosa came up short at 68 deg missing the record by 2 degrees. Offshore also wipe away the marine layer. No clouds and now marine layer lurking off the coast either. Therefore, clear skies expected tonight. As the winds continue to weaken under clear skies temperatures become the next weather impact for the near term. No change with ongoing Frost ADvisory/Freeze Warnings. See below. Key items we`ll be focusing on for the upcoming week: cold overnights continue with even colder temperatures possible next weekend, winds ramp up once again late in the weekend, and low chance for precip to region next weekend. MM && .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... (06Z TAFS) Issued at 831 PM PST Mon Jan 20 2025 Satellite continues to show clear skies across the terminals. Therefore, high confidence that VFR will prevail through the TAF period as the offshore winds will continue to bring dry conditions. Light offshore winds through the TAF period for most terminals. Winds will turn N/NW by Tuesday afternoon. Vicinity of SFO...VFR through the TAF period. Light winds overnight, with light to moderate NW winds by Tuesday afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR through the TAF period. Moderate SE drainage expected overnight. Winds turn NW by Tuesday afternoon. && .MARINE... (Tonight through next Sunday) Issued at 831 PM PST Mon Jan 20 2025 Offshore breeze across the waters through Tuesday, with moderate to strong breezes within the San Pablo and San Francisco Bays through early Tuesday morning. Winds calm after Tuesday through Thursday. Moderate seas will persist through Thursday with significant wave heights becoming rough by Friday. Possible gale force winds are expected Friday and into the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...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...None. && $$ SHORT TERM...Kennedy LONG TERM....Kennedy 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

855 FXUS66 KOTX 210611 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1011 PM 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... Tonight through Wednesday: With the region still under the influence of the ridge, stable, cold pattern will continue through the period. Upper level moisture topping the ridge will bring increasing mid to high level clouds to the Inland Northwest. These could produce isolated snow flurries through Tuesday morning. No accumulations are expected. Winds will see a brief increase during the afternoon hours with gusts into the mid teens. Temperatures are expected to increase slightly from the Monday lows. Highs will be in the upper 20s and low 30s. Lows will be in the teens and low 20s. A few ensemble members are showing some isolated pockets of single digits in the northern valleys. /JDC Thursday through Sunday: A trough is expected to drop southward across the Inland Northwest from Thursday afternoon through Friday, which would bring chances for wintry precipitation. Significant widespread snow accumulations aren`t anticipated, though it should be cool enough to bring snow or at least a rain/snow mix into the lower valleys. Northern ID and the Cascades are most likely to see amounts exceeding 1". As we head into next weekend, clear, dry, and cold conditions are forecast under a northeasterly flow aloft. /KD && .AVIATION... 06Z TAFS: A weak upper level disturbance will move across Washington and north Idaho prior to sunrise. Members of the High Resolution Ensemble (HREF) generate a band simulated reflectivity between 09-15z across the eastern third of Washington and north Idaho. Model soundings show very little deep moisture during this time frame, so it looks like flurries at most with no visibility restriction for GEG, SFF, COE, and PUW. Decreasing clouds are expected quickly following the passage of the disturbance Tuesday morning. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: The chance of flurries has been integrated into the TAFs with a PROB30 -SN for the airports along the Washington/Idaho border. NAM forecast soundings suggest the potential for a shallow layer of low clouds between 2000-4000ft around Spokane into north Idaho. It did something similar 24 hours and it didn`t pan out. And similar to last night, the latest NAM is the only HREF members to suggest low clouds. According to HREF probabilities, there is only a 10 percent chance of ceilings below 3000 feet on Tuesday. /GKoch ----------------------- 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 19 28 18 28 18 32 / 0 0 0 0 0 20 Coeur d`Alene 16 29 14 30 17 33 / 0 0 0 0 0 20 Pullman 20 29 20 32 22 36 / 0 0 0 0 0 10 Lewiston 22 35 23 36 26 41 / 0 0 0 0 0 10 Colville 14 27 13 26 14 29 / 0 0 0 0 0 20 Sandpoint 18 28 17 27 18 31 / 0 0 0 0 0 20 Kellogg 18 29 15 31 18 35 / 0 0 0 0 0 20 Moses Lake 22 31 22 32 22 34 / 0 0 0 0 0 0 Wenatchee 20 32 23 31 23 35 / 0 0 0 0 0 0 Omak 14 28 14 28 18 31 / 0 0 0 0 0 10 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$

206 FXUS66 KPDT 210621 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1021 PM PST Mon Jan 20 2025 .AVIATION...06Z TAFs...VFR conditions are forecast through the period for all sites with FEW-BKN clouds at or above 15kft. Sustained winds of 10 kts or less are expected (80% chance), with intermittent higher gusts of 15 kts at RDM/BDN/DLS/PDT (30-50% chance). Plunkett/86 && .PREV DISCUSSION... /issued 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 && .PRELIMINARY POINT TEMPS/POPS... PDT 22 39 22 37 / 0 0 0 0 ALW 20 38 24 37 / 0 0 0 0 PSC 18 38 25 37 / 0 0 0 0 YKM 18 37 21 37 / 0 0 0 0 HRI 21 38 25 37 / 0 0 0 0 ELN 16 38 22 36 / 0 0 0 0 RDM 21 46 21 44 / 0 0 0 0 LGD 18 38 19 39 / 0 0 0 0 GCD 18 42 19 43 / 0 0 0 0 DLS 26 45 28 42 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...90 LONG TERM....76 AVIATION...86

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. && $$

337 FXUS65 KBOI 210321 AFDBOI Area Forecast Discussion National Weather Service Boise ID 821 PM MST Mon Jan 20 2025 .DISCUSSION...Very cold conditions continue across southwestern Idaho and southeastern Oregon this evening. Clear skies and light winds are allowing excellent radiational cooling and temperatures are running about 5 degrees colder than they were at the same time last night. In fact, temperatures in the mountains have already fallen below zero in many areas. This will be the coldest night of the winter so far. The previous forecast describes the situation perfectly and no updates are needed this evening. && .AVIATION...VFR. Mostly clear. Surface winds: variable up to 10 kts. Winds aloft at 10kft MSL: N-NW 15-25 kts becoming W-NW 35-45kt Tues afternoon. KBOI...VFR. Surface winds: SE 5-10kt, becoming NW 5 kt Tues afternoon. && .PREV DISCUSSION... 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. && .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 DISCUSSION...JB AVIATION.....KA SHORT TERM...BW LONG TERM....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