307 FXUS66 KSEW 290445 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 845 PM PST Sun Dec 28 2025 .UPDATE...No changes made to the inherited forecast. Upper-ridge influence continues as its axis sits just offshore this evening. High pressure at the surface in concert with a weak surface trough along CA/OR coast is leading to light northerly winds across the CWA. Winds and mid to high clouds should keep widespread fog from forming. However, river valleys such as the Chehalis should remain socked in with freezing fog. The previous discussion remains below along with an updated aviation section: && .SYNOPSIS... An upper level ridge will continue to build over Western Washington and persist through midweek, bringing drier conditions and patchy fog to the region. An active weather pattern may return as early as Thursday, bringing back lowland rain and mountain snow into the weekend. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Latest satellite imagery shows mid to high level clouds moving over Western Washington this afternoon. As a result, the fog in the Chehalis Valley has struggled to scatter out this afternoon. An upper level ridge will be the prominent weather feature through at least midweek. This ridge will keep conditions dry across Western Washington. While conditions will remain dry, abundant lingering moisture may lead to patchy fog formation overnight, especially along the southern interior and Chehalis Valley. High temperatures will generally be in the mid to upper 40s. Low temperatures will be on the chilly side, with values in the low to mid 30s and upper 20s along the Chehalis Valley. With an upper level ridge in place, stable conditions may develop and lead to an inversion on Tuesday and Wednesday. This may lead to stagnant conditions to develop. 29 && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Long-range ensembles have the upper level ridge persisting over the region through at at least Wednesday, keeping conditions dry. Model solutions start to defer slightly on Thursday on the arrival of the next system. Depending on what scenario plays out, it will determine the next arrival of precipitation for the region. An active weather pattern is favored to continue into the weekend. The threat of minor coastal flooding increases late in the week. While there is uncertainty in the timing and strength of the system, at this time it does not appear to exacerbate coastal flooding. 29 && .AVIATION... Northwesterly flow will persist aloft through the TAF period as a upper ridge level ridge builds into the region. A thermal trough at the surface will build along the coast on Monday, allowing for low level flow to transition to more east- northeasterly. Mid to high clouds continue to stream in over the area as a frontal system moves into British Columbia this evening. As a result, low clouds and fog have not scattered out much for areas south of Puget Sound this afternoon. Conditions at terminals like KOLM in fog remain IFR, while conditions elsewhere remain VFR. Expect fog to expand for areas south of the Sound into Monday morning. With cold overnight temperatures, terminals like KOLM will likely see another round of freezing fog overnight. Winds trending more north-northeasterly this evening. The combination of mid to high level cloud cover and northeasterly winds may help mitigate fog development for terminals east of Puget Sound on Monday morning. KSEA...VFR conditions with light northerly winds between 3-6 kt, transitioning to the northeast tonight. While a few low clouds will be possible within the vicinity of the terminal on Monday morning, northeasterly winds may help limit fog potential and keep VFR conditions prevalent at the terminal through the period. 14/McMillian && .MARINE... High pressure will remain situated over the coastal waters through Wednesday. Meanwhile, a weak thermal trough will build along the coast on Monday. This will continue to promote offshore flow through the first half of the week. Seas ranging between 3-6 ft today will build to 6-9 ft late tonight into Monday as systems pass by to the north and a west-northwest swell moves into the coastal waters. Dense fog may develop over portions of the interior waters with clearing conditions and light winds during the overnight periods the over the next few days and will likely restrict visibilities across the waters at times. A more active pattern returns the second half of the week, with the next frontal system expected to move into the area waters on Thursday. This will allow for flow to transition back to southerly. Increasing winds and seas will likely bring the next round of headlines to the area waters. 14 && .HYDROLOGY... No river flooding is expected during the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

813 FXUS66 KPQR 282316 AFDPQR Area Forecast Discussion National Weather Service Portland OR 316 PM PST Sun Dec 28 2025 .SYNOPSIS...Very few weather concerns through Wednesday as high pressure dominates the area. A messy series of fronts will move inland as early as Thursday and persist through the remainder of the week. && .SHORT TERM...Now through Wednesday...A broad area of high pressure consumes the west with a digging trough well offshore. Current pressure as been measured around 1035 mb and will continue to intensify through the next few days. This pervasive ridge will lead to clearing and stable conditions as air density decreases due to cooler air settling in. This stable airmass will cause mixing to be nearly non-existant at night and therefore increasing chances for fog and frost Monday and Tuesday morning. The caveat to fog formation will be the timing of cold air to saturation. If temperatures drop to or below freezing before water droplets can form and the wet bulb temperature is below freezing, then frost is more likely to form. Now if saturation occurs before freezing then there is a higher probability for fog. The challenge lies with cloud cover. The cloud cover, especially in the southern Willamette Valley where it is pervasive, may insulate enough that temperatures do not drop nearly as low as models are attempting. Therefore, fog would be a more likely solution. Winds will remain generally north to northwesterly except through the Columbia River Gorge where diurnally driven drainage winds will dominate. There is some level of uncertainty in wind speeds within the Gorge, but overall the pressure gradient is the strongest in the morning hours, and especially on Tuesday as the ridge is at it`s peak and the strongest temperature change. Another factor to consider is the potential for air stagnation concerns. The stable atmosphere for this long and cold temperatures can limit mixing and cause mixing heights to lower. In the forecast, we are seeing heights around 1000 ft or lower overnight. However, transport winds are greater than 5 kt which would bode for just enough mixing. It is something to consider though. Overnight temperatures will fall below freezing throughout much of the forecast area. For those with bulbs still blooming, these temperatures may be cold enough to cause a "killing freeze". Areas most susceptible will be within the southern Willamette Valley, rural portions of Clark County, the Upper Hood River Valley and rural outskirts of the I-5 corridor. There is around a 30% chance of overnight lows of 30 degrees F or less tonight into Monday and around a 15% chance of similar temperatures on Tuesday morning within the southern Willamette Valley based on hi-resolution ensemble models. Lower probability elsewhere except in the aforementioned locations. Within the Upper Hood River Valley near Odell and Hood River, there is around a 5% chance of temperatures lower than 25 degrees F on Monday and Tuesday morning. The ridge appears to attempt to break down on Wednesday; though based on the strength of the system it will be a slow decay. Temperatures -27 && .LONG TERM...Wednesday Night through Sunday...Looking into the middle and latter part of the upcoming week, models are suggesting a pattern change for the region. However, there continues to be a great level of uncertainty in the long-term pattern due to the aforementioned ridge. The EPS ensembles are showing a weak closed low in the southeast Pacific that will slowly advect northward on Thursday. A frontal system stemming from a broad and very messy low pressure system in the Gulf of Alaska is dropping down at nearly the same time. The combination of these two features is making the overall pattern incredibly messy and uncertainty high. The NBM is showing rain initiating as early as Thursday where most of northwest Oregon and southwest Washington see around a 15-30% chance of rain. However, the GEFS and GEPS show rain starting that early afternoon. The ENS appears to be the faster of the solutions while the GEPS with the highest rain amounts. With all of this said, precipitation totals will be non-impactful and fairly typical for this time of year. Some models are attempting to show a secondary frontal band moving in on Saturday into Sunday but it is incredibly unorganized so it`s nothing to quite address at this point. -27 && .AVIATION...High pressure continues to build over the region supporting light northerly winds. Stratus throughout the Willamette Valley continues to erode from north to south but likely won`t completely clear over the southern portion of the valley. Expecting stratus to reform over the valley and along the Columbia river overnight. Guidance is still mixed on whether fog also reforms or not. Temperatures look to drop to near or below the freezing mark for most of the lowlands which would favor frost development instead of fog. Leaning towards this solution with stratus around 1000-2000 feet, locally lower. Stratus clears out again Monday morning as light north winds increase after 18z or so. KPDX AND APPROACHES...Expect VFR conditions into tonight with light north winds. Expecting stratus to redevelop and move into the area around 12z Monday morning, leading to sub-VFR CIGs for a time. Models do show uncertainty regarding the exact conditions with some showing fog development but others expect cooler conditions with frost which would inhibit fog development. /19 && .MARINE...High pressure remains in control of the region through the middle of the week. Winds expected to be northerly to northeasterly as a weak thermal trough develops at the surface. Winds 10 kts or less. Seas start out around 3 to feet but a westerly swell moves into the waters Monday morning, pushing seas to 7 to 8 feet at 11 to 13 seconds. There is potential for the pattern to become more active toward the end of the week but details are unclear at this time. /19 && .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

831 FXUS66 KMFR 290027 AFDMFR Area Forecast Discussion National Weather Service Medford OR 427 PM PST Sun Dec 28 2025 ...Updated AVIATION discussion for 00Z TAFs... .DISCUSSION...Forecast confidence has increased in the overall evolution of conditions during the next 10 days. An Air Stagnation Advisory has been issued for the southern Oregon valleys east of the Coast Range through Wednesday afternoon. An active pattern will follow Wednesday night or Thursday through the weekend, and at least into early next week. A weak shortwave will swing southeastward across Oregon tonight with an increase of high clouds. A few very similar others will follow during the next few days with similarly very modest effect. But, on a broader scale, high pressure will continue to build northeast into the region through Tuesday then linger on Wednesday as it begins to shift eastward. The result is that each of the next few days will have weather that resembles today`s conditions. This includes mainly, but not exclusively, west side night and morning valley fog and freezing fog, westside lows mainly in the upper 20s to lower 30s, eastside lows mainly in the teens, mostly clear skies and seasonable temperatures at the coast. Fog and freezing fog will have the hardest time breaking out in Josephine and Douglas counties. We will start out the first hours of the new year with increasing clouds and an increasing probability of light precipitation. A warm front lifting northward is forecast to result in snow levels around 6000 to 7000 feet. The center of the parent upper trough is expected to track across central California on Thursday, continuing what is likely to become a broader coverage of light precipitation in our area while snow levels remain high. Beyond Thursday, the finer details of the strength and timing of systems begin to diverge amongst the suite of models. But, a colder, stronger system is expected to track east-southeast from the Gulf of Alaska and across our area during Friday through Saturday. This track brings the highest probability that higher precipitation amounts will be focused on the coast, and western and southern Siskiyou County, secondarily into Josephine County and on the Cascades, with snow levels in our area dropping to more seasonably typical values of around 4000 to 5000 feet. This may be a light event away from the coast and Mt. Shasta region, perhaps not even warranting winter weather advisories elsewhere inland. But, southerly winds will at least become breezy to windy. Details diverge further beyond Friday, but another similar system to its immediate predecessor is likely during the weekend. && .AVIATION...29/00Z TAFs...VFR conditions prevail across most of northern California and southern Oregon this afternoon and through the TAF period under stable atmospheric conditions. MVFR ceilings remain in the Umpqua Valley. IFR/LIFR conditions look to return to the Rogue and Umpqua valleys overnight, with clearing possible by Monday afternoon. Slight signals remain for Klamath Falls to see some development early Monday morning fog, but confidence is minimal. Easterly flow will keep fog off the coast. -TAD && .MARINE...Updated 200 PM PST Sunday, December 28, 2025...Gusty north winds have produced steep seas mainly across the waters south of Cape Blanco and beyond 10 nm from shore. Gusty north winds and steep seas will expand late this afternoon and evening to include nearly all the waters south of Coos Bay. Conditions improve late Monday, with light south winds expected through Wednesday. Increased south winds begin late in the week ahead of the next series of frontal systems. -BPN && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Small Craft Advisory until 1 AM PST Tuesday for ORZ021. Air Stagnation Advisory until 4 PM PST Wednesday for ORZ023>026- 029>031. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 1 AM PST Tuesday for PZZ350-356-370-376. && $$

715 FXUS66 KEKA 282236 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 236 PM PST Sun Dec 28 2025 .SYNOPSIS...Drier and colder weather this weekend is expected to last through Tuesday. Light rain return from south to north Wednesday night into Thursday, followed by a frontal system with moderate to locally heavy rain, high mountain snow and gusty winds on Friday. && .DISCUSSION...Quiet weather conditions are observed across the region as surface high pressure strengthens and ridging aloft builds across the West Coast through Monday. Mostly sunny and seasonably cool temperatures are being observed across Northwest California today, with some interior valleys seeing slow clearing. Offshore flow (east-northeast winds) is expected to increase slightly across the interior ridges this evening into Monday, coinciding with increasing subsidence. Gusts from 25 to 35 mph are most likely into Monday morning over the exposed ridges in the eastern portion of Lake County. Winds are expected to diminish throughout the day as the surface pressure gradient relaxes. Low temperatures tonight/Monday morning are forecast to be a few degrees warmer than this morning`s readings, with coastal areas in the upper 30s to low 40s and interior valleys generally in the 30s. Areas of fog and patchy dense fog are anticipated along the shelter valleys. Ridging will continue to dominate the regional synoptics through Tuesday, maintaining dry and stable conditions. Adiabatic warming is expected to build Monday through Tuesday. Dry offshore flow, especially at night, will keep the air dry and promote a warming trend Monday and Tuesday. High`s generally in the upper 50s to mid 60s are expected, but any areas that do have fog develop overnight will likely be slow to clear and may be lower than forecast. This is above normal for late December. Latest operational model guidances shows the ridge will begin to weaken and shift eastward on Tuesday as a trough from Gulf of Alaska interacts with a subtropical cut- off low. A large swath of moisture in advance of the trough will spread northward from Central California on Wednesday (New Year`s Eve). Some light rain or sprinkles will be possible as early Wednesday night for Lake, Mendocino, southern Humboldt and southern Trinity counties. Expanded northward for northern Humboldt, northern Trinity and Del Norte early Thursday (New Year`s Day). 6-hourly rain rates increase to 0.10-0.20 inches with local maximums perhaps up to 0.35 inches in the King Range Thursday night into Friday morning. Highest rain rates will most likely occur with frontal passage on Friday. The CW3E Tools for GEFS and ECMWF EPS are showing an increasing chance (50-75%) of IVT greater than 250 kg/m/s arriving on Friday across the area. The GEFS and ECMWF ensemble controls are in a good agreement with IVT greater than 500 kg/m/s for the southern portion of the forecast area, including Mendocino and Lake counties. NBM probabilities of 24-hours precipitation exceeding 1 inch range from 30-45% for areas south of Cape Mendocino 4AM Thursday to 4AM Friday, with up to 60% for the King Range. While chances increase to 40-60% from 4 AM Friday to 4 AM Saturday, with 25-35% chances for northern Humboldt, northern Trinity and Del Norte counties. Stay tuned!/ ZVS&DUG && .AVIATION...High pressure building in and offshore flow kept the coastal areas clear this morning. This inland valleys saw widespread low clouds and fog across the area. This is slowly clearing out this afternoon, but is expected to quickly return tonight in most interior valleys. The coast will likely stay clear again with the offshore flow remaining in place. Monday the fog and low clouds are in the valley are expected to be slow to clear once again. MKK && .MARINE...The northerly winds are starting to diminish as high pressure builds overhead. A local area of southerly winds is expected to developer along the coast south of Cape Mendocino. The wind driven waves are also diminishing and pushing farther off the coast. A northwest swell continues to move through the waters and is around 5 feet at 12 seconds. Monday through Wednesday morning winds are expected to be fairly light, generally less than 10kt. A new swell is expected to build into the waters on Monday, initially it looks to be around 4 feet at 14 seconds. This is expected slowly build through Tuesday to around 5 or 6 feet at 14 seconds. Wednesday afternoon the winds are expected to start to turn southerly again head of the next system. There is still some uncertainty on the timing this far out, but it looks like they will start to increase Thursday morning. The models are showing the potential for gales as early as Thursday evening. Gales are more likely on Friday, although have kept the forecast to near gale force gusts at this point due to the lingering uncertainty. These southerly winds will also already high tides and may cause coastal flooding, see coastal flooding section. MKK && .COASTAL FLOODING...Another round of very high tides is coming up the 31st through 4th. At the North Spit Tide gauge on Humboldt Bay these are expected to be peak around 8.7 above MLLW on January 2nd and 3rd. There is still a lot of uncertainty on the winds, bu there is the potential for gale force southerly winds during this time period. The storm surge models are already showing nearly a foot of surge, but higher amounts are possible if the winds line up with the highest tides. This could yield quite a bit of flooding in the low lying areas around Humboldt Bay. Rain may also be occurring which exacerbate flooding surrounding Humboldt as creeks and low areas may not be able to drain during high tide. There are still a lot of variables, but this could bring 1 to 2 feet of saltwater onto to normally dry ground around Humboldt Bay. The impacts are less clear outside of Humboldt Bay and will be more driven by the wave size and running up much farther than normal. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until noon PST today for PZZ455. Small Craft Advisory until 6 PM PST this evening for PZZ470- 475. && $$ NOTE: The full forecast discussion is now regularly issued between 10 am/pm and 1 pm/am. Additional updates will be issued as needed. 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

180 FXUS66 KMTR 282325 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 325 PM PST Sun Dec 28 2025 ...New AVIATION... .KEY MESSAGES... Updated at 128 PM PST Sun Dec 28 2025 - Cold overnight conditions for interior and valley locations - Rain returns Wednesday and lasts through the weekend - Coastal flooding from King Tides is expected Wednesday through Sunday && .SHORT TERM... Issued at 128 PM PST Sun Dec 28 2025 (This evening through Tuesday) High pressure building into the Intermountain West and a coastal trough off the West Coast will dominate our weather through Tuesday. This is a textbook setup for offshore flow. Fortunately, we do not need to worry about fire weather concerns as we normally would. Instead, clear and dry conditions will yield cold overnight conditions. A Cold Weather Advisory has been issued for tonight for interior and valley locations. This goes for everyone but especially for those of you who are still without power: do not use generators or grills inside as carbon monoxide poisoning can result! Whether you are in the Cold Weather Advisory or not, it is going to be a cold night and a cold start to the week. Some grief was had over the minimum temperature forecast due to the aforementioned offshore flow. Why? Well, offshore flow can bring compressional/downslope warming. This is why the North Bay Interior Mountains were left out of the Cold Weather Advisory. 925mb flow (~2500 ft) from the ECMWF and GFS show 30 knots through there overnight. This will mix down warmer and drier air aloft which should help keep the area above 36 degrees. There is even a bust scenario where it mixes all the way down to the North Bay Interior Valleys, but that is not as likely. Another bust scenario is that the Northern Salinas Valley remains above 36 degrees with the help of moderate drainage winds. Nonetheless, the warming and drying trend will continue through Tuesday with cold overnight conditions. && .LONG TERM... Issued at 128 PM PST Sun Dec 28 2025 (Wednesday through next Saturday) Coastal flooding from King Tides returns Wednesday and lasts into Sunday. This will impact the Monterey Bay Shoreline, San Francisco Bay Shoreline, San Pablo Bay Shoreline, and the Pacific Coast. If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property. A pattern change is on tap for Wednesday as a surface low pressure system near the California/Mexico border picks up tropical moisture on its journey northward. ECMWF and GEFS ensemble IVT forecast shows their 80 member ensemble mean breaching 250 kg/ms during this time. It`s too soon to say with certainty, but minor flooding in low- lying, poor drainage, and urban areas as well as flashy creeks/streams can be expected as early as Wednesday. Tree debris from this past week that hasn`t been disposed of may act to clog storm drains and gutters, resulting in more flooding. Wind will increase during this time, but it is not expected to be impactful by itself. However, the combination of wind and moist soils will increase the risk for downed trees, especially where trees have recently been weakened. If you are looking for a sign to put away your outdoor holiday decorations, this is it. All outdoor preparations such as securing loose outdoor items, trimming tree branches, and cleaning out gutters should be finished by Tuesday. There`s also a low chance (<15%) for thunderstorms Wednesday into Thursday, but that will be heavily dependent on the exact trajectory of the low. The more impactful of the two systems looks to be Friday as a surface low pressure system and its attendant cold front come into Northern California. Both the deterministic ECMWF and GFS depict a 50+ knot 925mb jet accompanying it which may equate to a Wind Advisory for portions of the area (mainly looking at the coast and the higher terrain). The same rain impacts of minor flooding in low-lying, poor drainage, and urban areas as well as flashy creeks/streams can be expected during this timeframe. Deterministic and ensemble river forecasts do not show any mainstem river points reaching minor flood stage; however, this could be a result of QPF only recently trending up this morning after the river forecasts were already completed. HEFS does show a 10% chance of river flow exceedance for the notoriously flashy spots in Sonoma County of Russian River at Geyserville (GEYC1), Laguna de Santa Rosa at Stony Point Road NR Cotati (CTIC1), and Mark West Creek near Mirabel Heights (MWEC1) which finally dropped below action stage just as I was typing this. && .AVIATION... (00Z TAFS) Issued at 325 PM PST Sun Dec 28 2025 Offshore winds and VFR except tule fog /VLIFR-IFR/ from the Central Valley is forecast to reach into eastern Contra Costa county late tonight and Monday. Patchy valley fog /VLIFR-IFR/ also developing due to radiative cooling tonight and Monday morning. Vicinity of SFO...VFR. Northeast wind around 5 knots tonight and Monday becoming northwest near 5 knots Monday afternoon. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR. Onshore winds 5 to 10 knots becoming east to southeast 5 to 12 knots tonight and Monday morning. Winds becoming light and variable to locally onshore late Monday afternoon. && .MARINE... (Tonight through next Friday) Issued at 318 PM PST Sun Dec 28 2025 A gentle northerly breeze will gradually shift to easterly over the next 24 hours. Seas will remain moderate through Thursday. Overall marine conditions will remain favorable before the next low pressure system brings strong southerly winds and rough seas by Friday. && .BEACHES... Issued at 945 AM PST Sun Dec 28 2025 Perigean spring tides (king tides) return Wednesday - Sunday. This is due to the combination of the full moon on 1/3, lunar perigee on 1/1, and perihelion on 1/3. In other words all three planetary bodies are lined up and close to each other. In addition to the high astronomical tide, the incoming low pressure system will bring strong onshore winds, generating some storm surge. The combination of these factors will bring minor coastal flooding to the low-lying areas near shorelines and tidal waterways during high tide Wednesday through Sunday. At the San Francisco tidal gauge, high tide is expected to be 1.5 ft above normal at 7:51 AM Wednesday, 1.7 ft above normal at 8:41 AM Thursday, 1.8 ft above normal at 9:34 AM Friday, 1.8 ft above normal at 10:26 AM Saturday, and 1.6 ft above normal at 11:18 AM Sunday. These predictions include 0.5 feet of storm surge that will enhance the astronomical tide and flooding threat. High tide varies up to 90 minutes earlier or later along the Pacific Coast and through the San Francisco Bay, respectively. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Coastal Flood Advisory from 5 AM Wednesday to 2 PM PST Sunday for CAZ006-505-506-508-509-529-530. Cold Weather Advisory from 1 AM to 9 AM PST Monday for CAZ506- 510-513>518-528. PZ...None. && $$ SHORT TERM...Sarment LONG TERM....Sarment AVIATION...Canepa MARINE...Flynn Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, X, and YouTube at: www.facebook.com/nwsbayarea x.com/nwsbayarea www.youtube.com/nwsbayarea

204 FXUS66 KOTX 282253 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 253 PM PST Sun Dec 28 2025 .KEY MESSAGES... - Dry conditions through midweek then becoming unsettled late week into the weekend. && .SYNOPSIS... Dry and cold air remains over the region through Sunday. Temperatures moderate back to seasonal normals and dry conditions continue early next week, then a more active winter weather pattern returns heading into 2026. && .DISCUSSION... Sunday afternoon through Wednesday: The sun is out across much of the region this afternoon thanks to cold and dry notherly air keeping skies relatively clear. A ridge of high pressure will settle in over the Inland Northwest through the middle of the week, keeping conditions dry. A bit of moisture will sneak into the area out of the northwest bringing passing mid and high level clouds, but no precip is expected. Temperatures will slowly rise by a degree or two each day, climbing into the mid to upper 30s by Wednesday. Thursday through Saturday: There is good consensus among ensembles on the ridge axis shifting east by Thursday and making room for a trough to approach the coastline, which will place us in a more active southwesterly flow pattern. With this pattern shift will come in increase in chances for mountain snow and lowland rain or a wintry mix. At this point precip amounts look light with minimal impacts. There is only a 25% chance of 1.0" of liquid precipitation at the crest of the Cascades from Thursday to Sunday. For the Idaho Panhandle mountains, those chances decrease to between 5% and 15%. Chances for any lowland snow look confined to near the Canadian border. /Fewkes && .AVIATION... 00Z TAFs: VFR conditions continue across eastern Washington and north Idaho under a dry airmass. A small amount of moisture associated with weather systems moving into British Columbia will sneak in from the northwest bringing passing mid and high level clouds, but conditions are expected to remain VFR. Winds wil remain mostly light through the period, though an increasing easterly pressure gradient will result in east to southeast winds up to 10 knots at KPUW Sunday evening. .FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for widespread VFR conditions. ----------------------- Confidence descriptors: Low - Less than a 30 percent chance Moderate - 30 to 70 percent chance High - Greater than a 70 percent chance For additional probabilistic information for NWS Spokane airports,please refer to the Aviation Dashboard on our webpage: https:/www.weather.gov/otx/avndashboard && .Preliminary Point Temps/PoPs... Spokane 21 32 22 35 24 37 / 0 0 0 0 0 0 Coeur d`Alene 21 33 23 37 26 38 / 0 0 0 0 0 0 Pullman 23 34 24 38 26 39 / 0 0 0 0 0 0 Lewiston 26 37 27 39 29 41 / 0 0 0 0 0 0 Colville 17 31 19 35 23 37 / 0 0 0 0 0 0 Sandpoint 18 30 22 33 25 36 / 0 0 0 0 0 0 Kellogg 20 35 25 39 29 41 / 0 10 0 0 0 0 Moses Lake 23 35 22 36 23 35 / 0 0 0 0 0 0 Wenatchee 23 32 24 34 25 36 / 10 0 0 0 0 0 Omak 18 31 20 33 25 34 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$

398 FXUS66 KPDT 282230 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 230 PM PST Sun Dec 28 2025 .Key Messages... - Fog and Air Stagnation concerns as a high pressure ridge persists through Wednesday. - Precipitation chances with light mountain snow return Thursday onward. .DISCUSSION...Current radar and satellite imagery show clear skies across the forecast area with high clouds moving southward towards the Upper Slopes of WA Cascades. Patchy fog may develop tonight but will be localized for portion of mountain areas. A high pressure system will continue through Wednesday with fog remaining as a concern for these days during morning and overnight hours. Thanks to the northwest flow aloft, cooler air will bring nighttime temperatures to below freezing (mostly in the 20s) across the region along with dewpoints. That said, confidence is moderate (>50%) for freezing fog to develop. Visibilities could also be affected, but cannot rule out on the timing nor how dense the fog may actually get. NBM still favors less than 15% probability of 3 statue miles or less for visibilities. Air stagnation could potentially develop for Monday through Wednesday. With the mixing heights reaching to 1.5 kft or lower during morning and afternoon hours and transport winds less than 10kts, this concern could be borderline advisory-level, but we decided to hold off for now and continue monitoring in the meantime. Winds will be light across the forecast area with some breezes over the mountains. Models are in better agreement with the frontal system approaching the PacNW Thursday onward as the ridge gradually breaks down with the upper trough moving in. Additionally, this system will bring warm airmass, which will increase high temps by few degrees above average. Light showers will develop across the WA/OR Cascades before becoming more widespread overnight with light rain for the lower elevations and mountain rain/snow mix. QPF amounts may exceed to 0.10 inch or higher along the Cascades and other mountain areas but less for the low elevations. Snowfall amounts may exceed to an inch or lower over the crest of WA/OR Cascades and other mountain areas. However, the raw ensembles has a 10-20% prob for snowfall amounts no more than 0.5 inches. Feaster/97 && .AVIATION...00Z TAFs....Light winds will persist overnight as the area as high pressure continues to dominate the region. The return of stratus is of low probability (ranging between about 10 up to to 20 percent confidence) along terminals in the shadow off Cascades, (DLS/RDM/BDN) and to a lesser degree YKM based on HREF probabilities for MVFR and IFR cigs. Winds will be largely locally terrain driven and 5 knots or less. && .PRELIMINARY POINT TEMPS/POPS... PDT 23 37 21 35 / 0 0 0 0 ALW 25 34 25 34 / 0 0 0 0 PSC 22 35 22 34 / 0 0 0 0 YKM 22 35 21 37 / 0 0 0 0 HRI 24 35 22 33 / 0 0 0 0 ELN 20 32 20 34 / 0 0 0 0 RDM 20 44 20 45 / 0 0 0 0 LGD 22 38 25 41 / 0 0 0 0 GCD 23 43 25 47 / 0 0 0 0 DLS 28 38 26 38 / 10 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ DISCUSSION...97 AVIATION...71

846 FXUS65 KREV 282024 AFDREV Area Forecast Discussion National Weather Service Reno NV 1224 PM PST Sun Dec 28 2025 .KEY MESSAGES... * Much colder temperatures and dry weather prevails today with potential for freezing fog in the Sierra tonight. * Quiet weather with morning inversions leading to air stagnation is expected this week over western NV valleys. * There is potential for another series of winter storms starting New Years Day through next weekend. && .DISCUSSION... Light easterly breezes are expected today through mid-week. Colder air has moved in this morning, making our high and low temperatures 5 degrees below normal for this time of year through Monday. We`ll warm up each day after Monday into late-week with highs reaching up to 50 degrees and lows near 30. With the light winds this week, we may see morning valley inversions through at least Wednesday. There will be a 40-50% chance of freezing fog each morning through mid- week. Looking ahead to Thursday and beyond, the storm door has an increasingly likely chance to open up again. Ensembles show a 500mb trough moving in towards the end of the week, positioned near the coast. CW3E`s GEFS IVT plume doesn`t have much in the way of moisture for our latitudes, however the EC EPS IVT plume does. As such, ensembles and long range models are still in great disagreement, so timing and placement of any storms remains uncertain. But where we are confident is the fact that we`ll likely see another series of winter storms late-week into next weekend. -Justin && .AVIATION... VFR conditions prevail for much of the region over the next 24 hours with light winds. FEW to SCT mid to high level clouds today, becoming clear overnight tonight through Tuesday morning. FZFG has a 40-50% chance of building in for Sierra valleys between 08-17Z tonight-tomorrow morning, bringing likely IFR/LIFR impacts to KTRK and potentially KTVL. -Justin && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

537 FXUS66 KSTO 282012 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1212 PM PST Sun Dec 28 2025 .KEY MESSAGES... - Dry weather through mid-week with cold overnight lows and areas of frost and fog/mist/low clouds in the Central Valley - Next weather system moves in New Year`s Day bringing the potential for showers and mountain snow showers into the weekend, although confidence is low on details at the moment && .DISCUSSION... ...Today through Wednesday... Current GOES-West visible satellite imagery illustrates that the fog and stratus have lifted and are dissipating slowly this afternoon, with clear skies elsewhere. The upper level pattern will feature a ridge of high pressure over much of the region over the next few days, allowing for dry weather to prevail. Locally breezy offshore winds are expected in the typical N-E wind prone areas including the Sacramento Valley west of I-5, Delta, and mountain and foothill gaps and canyons. Strongest winds are expected in the evening through early morning hours with gusts to 15-20 mph in the Valley and 20-30 mph over higher terrain. The dense fog from this morning has lifted, and there is potential for another round of dense fog each overnight through morning periods through Wednesday. Be sure to give yourself extra time to reach your destination each morning, and slow down and use low- beams if you encounter fog! In addition, cold overnight temperatures will bring concern for sensitive vegetation in areas of frost tonight into Monday. A Frost Advisory has been issued from 1 AM through 9 AM Monday for elevations below 2,000 feet in the Motherlode, central/southern Sacramento Valley, Delta, and northern San Joaquin Valley. Low temperatures of 33 to 36 degrees will result in frost formation. Frost formation may be inhibited by northerly flow along and west of Interstate 5, or in areas where fog forms early on in the night. ...New Years Day through Saturday... While there is still quite a bit of uncertainty with the system late this week due to a decent spread in possible solutions, the latest forecast amounts from WPC/NBM have trended much wetter. The latest probabilities from the NBM depict a 40-60% chance of 12 inches of snow above pass level in the mountains late this week into the weekend. Probabilities have also increased for 1 inch of rain, with a 25-50% chance in the Valley and 45-65% chance in the foothills. Be sure to check back for details on this next system as we get closer, and view the latest forecast at weather.gov. && .AVIATION... Lingering IFR ceilings and visibilities associated with fog expected through late morning or early afternoon, particularly for the Sacramento Area terminals. Otherwise, VFR conditions are forecast to prevail through about 06Z Monday. Winds generally less than 12 kts, with the exception of the northern Sacramento Valley around KRDD and KRBL where periodic north gusts around 20 kt are forecast through the day. Possible return of MVFR/IFR ceilings and visibilities for the southern Sacramento Valley and northern San Joaquin Valley terminals after 09Z Monday with redevelopment of fog. && .STO WATCHES/WARNINGS/ADVISORIES... Frost Advisory from 1 AM to 9 AM PST Monday for Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-Northern San Joaquin Valley-Southern Sacramento Valley. && $$

949 FXUS65 KMSO 281859 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1159 AM MST Sun Dec 28 2025 .DISCUSSION... KEY MESSAGES: - Very cold mornings will continue through the first half of this week. - Developing inversions will likely lead to fog, stratus and poor air quality. Some of the coldest air so far this winter has settled over western Montana and north-central Idaho. Most areas saw temperatures drop into the single digits this morning, with several mountain valleys falling below zero. Some of the coldest spots were in north-central Idaho, where temperatures reached -13F at Gilmore Summit and -11F in Dixie. As high pressure strengthens over the region, so too will the valley inversions. This "lid" on the atmosphere makes it more likely that thick valley fog and low stratus will develop by Monday and Tuesday mornings. This stagnant air will also lead to concerns about poor air quality through midweek. While afternoon temperatures will rise slightly each day, this morning and Monday morning are expected to be the two coldest days of the week. We expect this stable pattern to remain until at least Friday, when a Pacific trough moves ashore. Confidence in the exact timing is currently low, as weather models disagree on when the high pressure will break down. About 10% of models show the weather changing as early as Friday, while the majority suggest the change will happen next weekend or early next week. Whenever this shift occurs, there is a risk of light freezing rain in the valleys as moisture moves over the cold air still trapped at the surface. Please stay tuned for updates as the week progresses. && .AVIATION...Some of the coldest air this season has settled over the Northern Rockies. Widespread single digit temperatures were observed, with several places seeing below zero lows in the broader valleys along the Continental Divide in western Montana. Temperatures will begin to moderate as we progress through the week, with this morning and Monday morning likely being the two coldest mornings. As the ridge strengthens, so too will the valley inversions. Valley stratus and/or fog will become a concern by Monday or Tuesday morning. && .AIR STAGNATION...A ridge of high pressure will strengthen over the Northern Rockies early this coming week. The ridge is expected to remain in place for most of the week, potentially breaking down as early as Friday. Air stagnation concerns may be realized by Tuesday of this coming week. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

260 FXUS65 KBOI 290342 AFDBOI Area Forecast Discussion National Weather Service Boise ID 842 PM MST Sun Dec 28 2025 .DISCUSSION...High pressure remains over the area tonight through Wednesday, continuing drier and colder conditions tonight through midweek. Valley temperatures will remain in the upper 20s tonight and mountain temperatures in the teens. Light winds expected from the E-SE, as valley inversions build in tonight. Peak valley temperatures are expected in the upper 30s tomorrow, and peak mountain temperatures in the upper 20s. Low mixing heights are expected tonight through Wednesday, favoring inversions over SE Oregon and the valleys of SW Idaho. && .AVIATION...Mostly VFR. Low chance of brief patchy fog and low clouds near KBKE and KMYL early tomorrow morning.. Surface winds: variable less than 5 kt overnight, becoming NE-SE 5-10 kt late tomorrow morning. Winds aloft at 10kft MSL: W 10-15 kt. KBOI...VFR with mainly clear skies. Surface winds: calm overnight becoming SE 5-8 kt tomorrow morning. && .AIR STAGNATION...An upper level ridge will build over the region Monday and remain overhead through Wednesday, creating stagnant conditions in the valleys with poor mixing and light winds as a temperature inversion strengthens. Daytime mixing heights will be below 2000 feet AGL through at least Thursday. An Air Stagnation Advisory is in effect for most valley locations through early Thursday. Haze and patchy fog possible in valleys due to inversions. Conditions may improve late Thursday or Friday as an approaching Pacific frontal system brings precipitation and increases mixing. && .PREV DISCUSSION... SHORT TERM...Tonight through Wednesday night...An upper level ridge building along the coast will move overhead Monday through Wednesday. This will bring dry and stable conditions with a temperature inversion that strengthens through midweek. Temperatures will gradually warm through Wednesday, especially at higher elevations that are above the inversion, but will see little change in the lowest valleys across southeast Oregon and far western Idaho where the inversion will be strongest. Highs by Wednesday will be 5-10 degrees above normal in most areas, except near normal in the Lower Treasure Valley due to the inversion. Overnight lows will be cold (10s and 20s) with mostly clear skies and a cool airmass in place. This will also allow patchy valley fog to develop, although dry air will limit potential. Winds will remain light under this pattern. LONG TERM...Thursday through Sunday...A much more active pattern will redevelop during the extended. A deep trough off the coast will help to steer a weaker trough near the California coast northward. This weaker trough will be accompanied by subtropical moisture, and rain/snow chances will increase from the south on New Year`s Day, reaching 40-70% Thursday night and Friday. This moist airmass, due to its origin in the subtropics, will be mild and snow levels will rise to 5000-6500 feet (possibly as high as 7500 feet). The deep trough off the coast will send shortwave impulses inland over the weekend, bringing a 30-50% chance of rain and high elevation snow. These impulses should gradually bring cooler air aloft into our area with snow levels lowering to 3500-5500 feet. Moderate precipitation totals are expected Thursday through Sunday with significant snow accumulations limited to higher peaks. Winds will mostly be light, but could tick up over the weekend as the shortwaves move through. Temperatures through the period will average 5-10 degrees above normal. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Air Stagnation Advisory until 10 AM MST Thursday IDZ012-014-016-028-033. OR...Air Stagnation Advisory until 10 AM MST /9 AM PST/ Thursday ORZ061>064. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise DISCUSSION...JY AVIATION.....SA AIR STAGNATION...JY SHORT TERM...ST LONG TERM....ST

147 FXUS65 KLKN 282018 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1218 PM PST Sun Dec 28 2025 .KEY MESSAGES... Updated at 1213 PM PST Sun Dec 28 2025 * Warming trend to begin Monday lasting through New Years Eve. * Winds will generally remain light through the week. * Precipitation chances return for New Years Day into friday and again for the first half of the weekend. && .DISCUSSION... (This evening through next Saturday) WEATHER PATTERN OVERVIEW: 2025 on track to depart with quiet weather, light winds, and cool morning lows, however 2026 looks to start on the wet side. Upper level ridge in building across the Silver state from the northern California coast. This will keep the region dry through New Years Eve. However this ridge will quickly break down New Years Day Thursday as a pair of upper level troughs make there way to Nevada. The first upper trough will move in from southern California, and again looks to be a mild Pacific system with some more tropical moisture being drawn in from the Eastern Pacific. That means another mix of lower to mid elevation rain, and mountain snow, that begins early New Years day across central Nevada shifting NE into eastern Nevada by early evening before departing Friday morning. Amounts with this system look to be decent, rain wise as Valleys and lower elevation passes look to get between 0.10 and 0.75. Humboldt county looks to be drier as this systems track will be more of a graze, but will still get between 0.05 and 0.35 of water. Snow levels will be high at around 7500 feet, with mountains like the Rubies seeing between 4 and 8 of new snow. After a brief break Friday afternoon, a second upper level trough will move in for early Saturday morning lasting through Sunday morning. This system looks to be only slightly cooler than the first, but similar to the first, will also have a tropical moisture component but it wont be as strong. Models show snow levels starting at around 7000 feet dropping to 5500 feet by Sunday morning although timing of the cooler air still looks to be uncertain given high variation in model ensembles. Overall for valleys and lower elevation passes the dominant p-type will be rain with most areas seeing between 0.05 and 0.40 of rain. For Elevations between 5500 feet and 6500 feet there will be a transition to snow with up to 1 of snow possible. Mountain ranges will be the snow winner with this system as between 2 to 10 of new snow will be possible above 6500 feet. Temperatures which will be warming through New Years Eve will plateau New Years Day and Friday before cooling with the second system to be closer too, but still above seasonal normal. FORECAST CONFIDENCE & DEVIATIONS: There is high confidence for Quiet weather, light winds, and warming temperatures through New years Eve. There is moderate confidence in the chances for rain and high elevation snow across Central and eastern NV New years Day into Friday morning. There is moderate confidence in the valley rain and mountain snow showers for Saturday into Sunday morning. There is low confidence in the timing of rain changing over to snow for elevations above 5500 feet Saturday afternoon into Sunday morning. && .AVIATION... VFR conditions are forecast to be the primary flight conditions through Monday. With light winds and recent moisture there will be a low 10% to 20% chance for VCFG and vicinity freezing fog at area terminals. The highest chances for fog look to be during the early morning hours just before and after Sunrise. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...98 AVIATION...98