999 FXUS66 KSEW 281028 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 230 AM PST Sun Dec 28 2025 .SYNOPSIS... High pressure over the area will keep conditions generally dry but allow for colder overnight temperatures and likely morning fog development into early this week. A return to a more typically active pattern of lowland rain and mountain snow is expected late in the upcoming week. && .SHORT TERM /TODAY THROUGH TUESDAY/... Latest radar imagery living up to what the building upper level ridge promises with no echoes present in the CWA. Current satellite shows the other thing that comes with upper level ridging this time of year as some fog is very present in some valleys, especially in the SW interior and the Chehalis river valley. Not to be left out, latest obs are showing some pretty chilly temps this early morning with most lowland locations reporting upper 20s to lower 30s. Models remain consistent that this is going to be the way it is for the short term as the upper level ridge continues to build and the ridge axis slowly makes its way eastward. Outputs 24 hours ago suggested a flattening of the ridge around Tuesday but latest data suggests more of just a stop in the ridge building than any real flattening per se. That said, forecast is largely just a continuation of dry conditions, cold overnight lows in the lower 30s /mid 30s for water adjacent locations/ and the potential for overnight/morning fog. One minor thing to discuss is that the nBM wants to allow for a little bit of spill over from a system passing to the north over the ridge...bringing some Slight Chance to low-end Chance PoPs to the NW corner of the Olympic Peninsula. This feels a little overdone as ensembles completely flatline when it comes to PoP and QPF here in the short term...but ultimately, the chances are low enough where their inclusion does not alter current messaging. High temperatures will hang out in the low to mid 40s during this period. 18 && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... 24 hours ago, there was a bit of a rift between deterministic solutions and ensemble outputs...deterministic models holding the breakdown of the ridge off until late week while ensembles kept things on track for the next frontal system coming in by Wednesday. At the time of this writing, solutions have pretty well aligned, as both sides of the fence agree on keeping precip out of the forecast until the new year. While some ensemble members continue to suggest precip working its way into the area as early as Wednesday afternoon, the general consensus /and ensemble mean/ is that this activity will hold off until Thursday afternoon. Once the precip moves in, however, it is back to the races...so to speak...as the first system looks to be an upper trough moving northward from CA, followed quickly by a deepening trough over the Pacific pushing through for much of the day Saturday. This far out, it is a little early to assess teleconnections and whatnot...but models are hinting at a potential atmospheric river for the Saturday system. At this time, this seems to be more pointed toward northern CA...but this will be something to monitor as next weekend gets closer and as solutions likely change. As clouds start to move into the area for the second half of next week, overnight lows will get a bump upward, generally in the upper 30s to lower 40s while daytime highs see a more meager incremental increase...ranging in the upper 40s to around 50. 18 && .AVIATION... Generally VFR early this morning with areas of IFR/LIFR fog and low stratus generally south of the Puget Sound. Northwesterly flow aloft will persist through the TAF period as an upper level ridge over the northeastern Pacific builds into the area from the west. As skies continue to clear into the morning, fog will continue to expand across the south Sound and interior generating a range of MVFR to LIFR conditions for a few hours this morning. Conditions will scatter out by the late morning, with terminals returning to VFR by the afternoon. Surface winds will remain light around 3 to 8 kt, gradually shifting back to southerly this morning. KSEA...VFR this morning with easterly winds slowly shifting southerly throughout the morning, with light speeds generally 6 kt or less. Low stratus is possible in the vicinity of the terminal between 12Z-18Z this morning, with a high chance (45% to 50%) of MVFR conditions developing at the terminal. Conditions are expected to improve to VFR by the late morning, with more of the same on tap later this evening. 15 && .MARINE... High pressure will continue to build across the coastal waters this morning and remain situated over the region into early next week. Seas will continue to subside towards 3-6 ft throughout the day today, though systems passing by to the north will allow for seas to build back towards 6-9 ft again by Monday. Dense fog may develop over portions of the area waters with clearing conditions and light winds during the overnight periods the next few days and will likely restrict visibilities at times. The next front then looks to drop down into the area waters by late Wednesday into Thursday, which will likely bring the next round of headlines to the area waters. 14/15 && .HYDROLOGY... No river flooding in the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

745 FXUS66 KPQR 281116 AAA AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 313 AM PST Sun Dec 28 2025 .SYNOPSIS...High pressure builds through the middle of the week, which will bring cold mornings along with fog/frost development overnight with light winds. A pattern shift is likely for the latter part of the week. && .EARLY MORNING UPDATE...Dense Fog is being observed via ground observations across the I-5 corridor this morning. Therefore, have issued a dense fog advisory as visibilities could be reduced to 1/4 mile or less at times. Conditions are expected to improve as the sun rises with the fog scouring out around 10 AM this morning. /42 .SHORT TERM...Now through Tuesday Night...A broad area of high pressure over the eastern Pacific will slowly build in over the Pacific NW through the early part of the week. This will result in clearing skies, weak offshore winds, relatively dry conditions and cold nights. What this means, is that the CWA is in store for a brief break from the very active pattern of early/mid December. Given the rather stable environment, we have a few potential scenarios that could manifest: 1) Fog. Fog is quite common this time of year under these patterns due to low level inversions via radiational cooling, recent moisture, and light north to east winds. In addition to these variables, we must also consider that overnight lows through Tuesday night/Wednesday morning will be overnight low temperatures will be near freezing or a few degrees below freezing in many areas and this will also inhibit fog formation. 2) Frost. Given the information, we must consider frost development over fog development a.k.a "frosting out" meaning that with light winds and cold temperatures will result in ice crystals forming in the air before water droplets and fog can form. 3) Air stagnation. Lastly, with very little air movement over the region because of the upper level high pressure. A persistent, subsidence inversion will result in very low mixing heights which will inhibit the lower levels (near surface) air with fresh air from higher elevations within the atmosphere. Thus leading to air stagnation concerns. Overall, looking at very little change through mid-week with very minor weather inconveniences. /42/27 .LONG TERM...Wednesday through Saturday...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 talked about in the short term discussion above. Deterministic models are showing a low pressure system attempting to build off the southern California coast as well as within the Gulf of Alaska, and these systems could break down the ridge over the Pac NW. We will continue to monitor these scenarios as models are slowly coming into better and better agreement. While we are well into winter and these systems are typically colder, the systems looking to push out the ridge of high pressure are showing 850 mb temperatures around 4C to 8C. So, no low level snow at this point is not in the cards. /42 && .AVIATION...Current radar and satellite imagery, along with terminal observations show widespread VFR conditions with intermittent pockets of MVFR to LIFR conditions. High pressure will be the dominant feature over the region through at least late Wednesday/early Thursday. This will result in slowly clearing skies, relatively light east/northeast winds and drying conditions. Therefore, expect predominately VFR conditions during the daytime with mostly VFR conditions expected overnight. However, with the aforementioned conditions, this will result in favorable frost/fog development within the Willamette Valley each night as overnight temperatures are expect to fall towards freezing or a few degrees below. Currently, conditions are favoring fog development, but cannot rule out some frost development. Guidance suggests a 40-60% chance for LIFR/IFR conditions across the Willamette Valley developing between 12Z-18Z Sunday. Any fog/frost that does develop should scour out and any lowered flight conditions should return to VFR after 18Z-20Z Sunday. Along the coast, conditions remain VFR as light offshore flow prevails. KPDX AND APPROACHES...VFR conditions until around 12Z Sunday. 50-70% chance for LIFR/IFR conditions developing as a result of fog between 12Z-18Z Sunday. With freezing/near freezing overnight temperatures, frost could develop over fog. Any fog/frost that does develop should scour out and any lowered flight conditions should return to VFR after 18Z-20Z Sunday. /42 && .MARINE...High pressure builds over the waters along with a weak thermal trough along the coast, bringing east-northeasterly winds under 15 kt through Tuesday. Seas 3 to 4 ft, with seas re-building towards 6 to 8 ft Monday/Tuesday as a fresh west-northwest swell moves in. A more active pattern looks to return to all waters towards the latter part of this week. /42/10 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Dense Fog Advisory until 10 AM PST this morning for ORZ108>118. WA...Dense Fog Advisory until 10 AM PST this morning for WAZ204>207. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

882 FXUS66 KMFR 281451 AFDMFR Area Forecast Discussion National Weather Service Medford OR 651 AM PST Sun Dec 28 2025 .DISCUSSION...Aviation Discussion Updated. && .AVIATION...28/12Z TAFs...A weak disturbance moving overhead has brought high clouds inland. These clouds are shifting eastward early this morning. Offshore flow will minimize chances for overnight/morning low clouds and fog development along the coast, but inland valleys will see IFR to LIFR conditions this morning. Low clouds and areas of fog have developed in the Umpqua Valley (including Roseburg), the Grants Pass area, as well as the Illinois Valley. Guidance and model soundings support low clouds or fog developing in the Medford area. However confidence is low for IFR or LIFR at Medford this morning due to light surface winds of 2 to 3 kt. Low clouds and fog will clear in the late morning and early afternoon with VFR expected areawide. East of the Cascades, conditions are mainly VFR with only isolated low clouds or fog. late tonight and Monday morning, valley fog and LIFR is expected to develop once again, including at Roseburg, Grants Pass and Medford. && .PREV DISCUSSION... /Issued 257 AM PST Sun Dec 28 2025/ DISCUSSION...A weak upper level disturbance is moving down the eastern side of the Pacific high and across the area this morning. This is bringing high clouds into the area. The high pressure ridge, centered just offshore, will strengthen over the area today, then remain in place through Wednesday. This pattern will bring stable and dry weather to the area with light easterly flow over the ridges. Valleys are expected to see nighttime and morning fog or low clouds. Overnight, areas of low clouds and fog have developed in the Umpqua Valley and Grants Pass areas. As high clouds shift eastward early this morning, expect partial clearing over the Medford area with chances for fog to develop in the morning hours. Further east and south, confidence is lower and high clouds may limit the development of fog and low clouds. National Blend of Models continues to show chances (20%) for low clouds and fog developing in the Klamath Basin though. Fog and low clouds is expected to clear in the late morning and early afternoon. Temperatures today will trend slightly warmer compared to yesterday for most areas. This gradual warming trend continues through Wednesday. The amount of valley fog may vary each day. However, guidance indicates fog and low clouds are likely in valleys during the overnight and morning hours tonight through Wednesday due to lingering boundary layer moisture combined with stable conditions, light winds and clear skies. In addition to valley fog, the high pressure over the area will bring a potential for stagnant air conditions, with limited mixing and light winds. We are monitoring for air stagnation conditions and will update as needed. Late in the week, model solutions continue to point to a more active weather pattern developing with low pressure system moving towards the area from the northwest and another low moving up from the southwest. This pattern will result in chances for precipitation moving into the area beginning around New Year`s Day. For details on this pattern, please see the extended discussion below. MARINE...Gusty north winds and steep seas are occurring this morning over the waters south of Cape Blanco beyond 10 nm from shore. Gusty north winds and steep seas will expand late this afternoon and evening to include the waters south of Bandon beyond 5 nm from shore and the waters between Coos Bay and Bandon beyond 10 nm from shore. Winds and seas will lower Sunday night into Monday morning, then remain relative light through Wednesday. PREV EXTENDED DISCUSSION... /Issued 329 PM PST Sat Dec 27 2025/ DISCUSSION...Beyond Wednesday afternoon, a broad trough in the Gulf of Alaska, and a weaker (but, potentially developing) trough offshore from central California will shift toward the west coast. The NBM looks a highly appropriate solution for the latter part of the week, indicating gradually increasing precipitation chances, with the highest probability Thursday night into Friday night. The ECMWF ensemble, in comparison with the GEFS, has a more sizable minority of members that more strongly deepen the Californian trough and would create a scenario around New Year`s Day with some resemblance to the weather of Christmas Day. This would be relatively high snow levels (above 4500 feet or higher), but with moderate to heavy precipitation for northern California. Of higher probability is that the flow aloft will more broadly split with our region affected by the generally weaker southern portion of the northern branch of the jet stream. This would be colder, placing snow levels around 3000 to 4500 feet, but with lower precipitation amounts than in the aforementioned scenario. More in the realm of potential Advisory level snowfall late in the week with a focus for the Cascades, rather than a Warning event. Please stay tuned for updates. && .MFR WATCHES/WARNINGS/ADVISORIES... OR...None. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory from 4 PM this afternoon to 4 AM PST Monday for PZZ350-356-370-376. && $$

725 FXUS66 KEKA 280909 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 109 AM PST Sun Dec 28 2025 .SYNOPSIS...Drier and colder weather is expected to last into Tuesday. Periods of mostly light rain and high mountain snow are forecast to return Thursday and Friday. && .DISCUSSION...Dry and seasonably cold weather is forecast to continue into early next week as a ridge aloft builds over the area. Mean sea level pressure pattern will continue to favor dry offshore flow with chilly nights for the the coast. A few coastal sites may dip down to 32F or less around Humboldt Bay early this Sunday morning. NBM continues to indicate a 96% chance for McKinleyville and a 70% chance for Arcata. Light NE and E winds may keep temperatures from falling to 32F. A frost advisory is in effect until 9 AM Sunday. Frost for coastal areas will be possible again tonight or early Monday morning. Adiabatic warming is expected to build Mon through Wed. Daytime highs will increase, especially for the higher elevations with southern sun exposure and in broad N-S oriented valleys. High`s in the lower to mid 60`s are expected. This is above normal for late Dec. Early morning lows will still be near or below freezing, however. After multiple days of rain, fog and low clouds will invariably form each night in the interior valleys. High temperatures may not warm much in valleys with stubborn and persistent low clouds and fog. Coastal areas will generally fair better with only shallow morning ground fog around Humboldt Bay and occasional high clouds. The ridge will begin to weaken and shift eastward on Wednesday as a Gulf of AK trough interacts with a subtropical cut-off low. A large swath of moisture in advance of the trough will spread northward from Central California on Wed. Some light rain or sprinkles will be possible as early Wed night for Lake and Mendo counties. 6-hourly rain rates increase Thu-Fri generally under 0.10 inches with local maximums perhaps up to 0.35 inches in the King Range Thu night or Fri morning. Highest rain rates will most likely occur with frontal passage on Fri. IVT with most ECMWF and GFS ensemble members are under 250kg/m/s. Impacts from rain or mountains snow appear minor at this point. && .AVIATION...With Northwest California solidly between systems and ridging building aloft, winds have become light and radiational cooling is causing temperatures to fall rapidly. With recent rainfall across the region, fog will easily form across the interior valleys. It is highly lightly that LIFR conditions will develop in many valleys including UKI. Less low clouds are expected at the coast, especially with high level clouds spreading over the area. Interior valley fog will slowly mix out on Sunday with some interior valley locations remaining in the fog into the afternoon hours. VFR should prevail at the coast. /RPA && .MARINE...Northerly winds will diminish overnight as ridging begins to build over the west coast weakening the surface pressure gradient over the waters. Winds and seas will remain generally low through midweek. The next storm system will approach the waters Wednesday into Thursday allowing winds to turn out of the south. Model guidance is indicating this next storm will not be particularly strong and winds may turn back out of the north rather quickly behind the passing front. The main concern on the horizon is a northwesterly fresh swell that could build into the waters late in the week to possibly next weekend. /RPA && .COASTAL FLOODING...King Tides are predicted to return next week. Highest probabilities for salt water inundation of normally dry areas will be around Humboldt Bay during high tide from Tue, December 30th to Mon, January 5th. Highest tidal predictions for Humboldt Bay are expected Fri and Sat. Strong southerly winds and a large tidal anomaly may result in levels near 9.6 feet above MLLW. Other coastal areas are less certain. Noyo harbor, Arena Cove, Crecent City harbor and Shelter Cove may also have minor salt water inundation. && .EKA WATCHES/WARNINGS/ADVISORIES... CA... Frost Advisory from 2 AM to 9 AM PST Sunday for CAZ101. Frost Advisory until 9 AM PST Sunday for CAZ103-109. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until noon PST Sunday for PZZ455. Small Craft Advisory until 6 PM PST Sunday for PZZ470. Small Craft Advisory until 8 PM PST Sunday for PZZ475. && $$ 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

544 FXUS66 KMTR 281141 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 341 AM PST Sun Dec 28 2025 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 235 AM PST Sun Dec 28 2025 - Dry weather, with cold nights through Wednesday morning. - Increasing confidence in wet weather returning mid to late week, due to a pattern change. && .SHORT TERM... Issued at 235 AM PST Sun Dec 28 2025 (Today and tonight) High clouds are visible on satellite imagery this morning, currently tracking into the Bay Area. This has made for an interesting forecast around these areas, particularly the North Bay where fog has developed. Pockets of colder air can be found there, but as of this time, not enough to warrant a Cold Weather Advisory. In fact, looking south to where the Cold Weather Advisory is in place, temperatures generally look to be on track. There is some concern for the low temperature forecast around the North Salinas Valley and areas near Hollister given dew points haven`t really fallen past the upper 30s at this time. Depending on how temperatures pan out this morning, we may be able to end the Cold Weather Advisory early if temperatures don`t fall. Looking at the rest of today, high clouds continue to advance southwards. High pressure builds over the eastern Pacific which will pinch off part of the upper level trough. Highs today will be a few degrees warmer than yesterday. An area to watch will be Sunday night into Monday. Ridging continues to build in over northern California, and another upper level trough forms over the Sierra, gets cut off, and then pushes into southern California. This should allow for mostly clear skies and perhaps some weak overnight offshore flow. The low temperature forecast will be the other challenge in the near term. Right now we flirt with Cold Weather Advisory conditions over the North and East Bay valleys, as well as the southern Salinas Valley. Given some of the guidance from the MOS has trended a bit warmer, opted to not issue anything this far out. The coldest temperatures from these areas look to be between roughly around 12- 15Z, before warming above criteria by late morning. && .LONG TERM... Issued at 235 AM PST Sun Dec 28 2025 (Monday through Saturday) Ridging holds through Tuesday, before it gets pushed over the PacNW. To the north, low pressure from the Gulf of Alaska forms and begins to digs southwards. To the south, the cut of low meanders and slowly drifts northward. This system should get picked up by digging trough to our north. Ensembles favor wetter weather starting Wednesday, with the QPF clusters showing a spread of rain solutions across California. The NBM guidance matches this, thus opted to leave that in. Looking at the GEFS and ECMWF ensemble, periodic rounds of rain look possible through the weekend. Timing, placement, and intensity will continue to unfold as we get closer to the event. && .AVIATION... (06Z TAFS) Issued at 935 PM PST Sat Dec 27 2025 The larger scale WMC-SFO pressure gradient will strengthen tonight through Sunday night resulting in offshore winds reaching the Bay Area. A mainly clear sky will help with radiative cooling and patchy fog redevelopment tonight and Sunday morning. Will also have to monitor tule fog redevelopment in the Central Valley and the potential for a return of tule fog into the Bay Area, though at the time being the HRRR model shows greater tule fog development Sunday night into Monday. The offshore winds develop before then, tule fog development and transport of tule fog could start as soon as early Sunday morning due to recent rains and moistened boundary layer. KSTS and KAPC have fog in the TAFs due to nocturnal radiative cooling, otherwise it`s a moderate to high confidence VFR forecast for the remainder of the terminals. Vicinity of SFO...VFR. Mainly northeast winds 5-7 knots tonight through Sunday night. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR. Winds east-southeast 5-10 knots and continuing into early-mid Sunday afternoon, then becoming light and variable to light onshore in the late afternoon. Light east to southeast winds redevelop Sunday night. && .AVIATION... (12Z TAFS) Issued at 336 AM PST Sun Dec 28 2025 Very quiet conditions with VFR expected through the TAF period for most terminals. Exceptions will be North Bay terminals where isolated FG is anticipated during the pre-dawn hours. Light offshore NE flow keeps most other locations dry with light winds. Generally a high confidence forecast...exception is how long the FG persists (or not) at KSTS/KAPC. Vicinity of SFO...VFR. Winds out of the NE for most of the period, but expected to remain light and not impactful. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR. Light offshore winds. High confidence. && .MARINE... (Today through Friday) Issued at 336 AM PST Sun Dec 28 2025 Light northerly breezes, moderate seas, and high pressure prevail through the first half of this week. Next chance for showers over the waters by the end of the week as a low pressure system moves in from the south. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Cold Weather Advisory until 9 AM PST this morning for CAZ516>518- 528. PZ...None. && $$ SHORT TERM...KR LONG TERM....KR AVIATION...Behringer MARINE...Behringer 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

672 FXUS66 KOTX 281151 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 351 AM 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... Today through Wednesday: Sunday will be the coolest day of the week as a departing system brought in cooler and drier Canadian air. High temperatures will reach into the 20s and 30s. The morning will start chilly in the single digits to low 20s. Although high pressure is building, there is a small chance (10-20%) of snow showers near the Cascade crest Sunday afternoon as moisture on the southern periphery of an atmospheric river moves into the region. Conditions look dry through the rest of the year (through Wednesday) as the ridge slowly shifts east. Temperatures begin to climb back above normal by Tuesday in the mid to upper 30s. Thursday through Sunday: Ensembles are in good agreement of troughing in the eastern Pacific by Thursday signaling the return of unsettled conditions. Precipitation amounts do not look overly impressive through late this week. There is only a 20-40% 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 5-20%. The best chances for any lowland snow will be confined to near the Canadian border under this pattern. DB && .AVIATION... 12Z TAFs: Much drier air in place has resulted in widespread VFR conditions across eastern Washington and north Idaho. Nighttime microphysics satellite imagery shows low clouds in the upslope side of the Blue Mountains, with the HREF holding onto a 10-20 percent chance of ceilings below 3000 feet at KPUW this morning, but confidence in these ceilings spreading into KPUW was not high enough to include in the TAF. As an upper level ridge shifts into the Pacific Northwest today, moisture associated with weather systems moving into British Columbia will stream in from the northwest. There is high confidence for passing mid and high level clouds, but the NBM and LAMP probabilities are giving a 40-50 percent chance for ceilings below 3000 feet from the lee of the Cascades through the central and northern Idaho Panhandle and a 20 percent chance across southeast Washington and the southern Panhandle Sunday evening. Model soundings and the HREF are not as confident in this though with a 20 percent chance at KGEG- KSFF- KCOE. Given how dry the boundary layer is at this moment, confidence of this coming into fruition is low and would like to see more support by high resolution models before including in the TAFs. Winds are expected to generally remain light through the period, though an increasing easterly pressure gradient will result in east to southeast winds up to 10 knots at KPUW late Sunday morning and evening. .FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for widespread VFR conditions. Low confidence for MVFR ceilings at KPUW-KLWS-KGEG-KSFF-KCOE. ----------------------- 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 29 22 33 22 35 24 / 0 0 0 0 0 0 Coeur d`Alene 28 21 33 24 36 24 / 0 0 0 0 0 0 Pullman 31 23 35 24 38 27 / 0 0 0 0 0 0 Lewiston 33 26 37 28 39 29 / 0 0 0 0 0 0 Colville 28 18 31 19 35 23 / 0 0 0 0 0 0 Sandpoint 26 21 32 24 36 24 / 0 0 0 0 0 0 Kellogg 28 21 35 26 40 27 / 0 0 0 0 0 0 Moses Lake 33 23 35 23 36 23 / 0 0 0 0 0 0 Wenatchee 30 23 32 24 33 24 / 0 0 0 0 0 0 Omak 28 21 32 24 34 25 / 0 10 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...None. ID...None. && $$

027 FXUS66 KPDT 281122 RRA AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 244 AM PST Sun Dec 28 2025 .KEY POINTS... 1. A high pressure ridge will dominate through mid-week 2. Fog will be the main concern through mid-week 3. Likely return of precipitation late next week .DISCUSSION... Current satellite shows no returns over the region with nighttime satellite showing mostly high clouds in the area that are quickly moving southward. Northwest flow aloft is advecting cooler air into the region tonight which will bring overnight temperatures into the teens to low 20s in most areas with only the Basin, foothills and the Gorge seeing temperatures in the upper 20s. Models show the weak shortwave that came through last night to be mostly out of the region leaving northwest flow aloft. As stated above, this will bring below average temperatures to the region overnight and through tomorrow. By Sunday morning, the leading edge of the upper level ridge will begin moving over the region. Models are in form agreement and show the high pressure will dominate the region through the mid-week with steadily increasing temperatures. However, climate shows that the Basin and foothills will remain slightly below normal seasonal temperatures while elsewhere will see slightly above average. 100% of all raw ensembles show that all locations will be below 40 degrees Sunday, everywhere except central OR on Monday while steadily increasing to the eastern mountains Tuesday and Wednesday. Temperatures will be steady in the upper 30s to low 40s for most locations through Wednesday with 40-60% of the ensembles having central OR in the upper 40s to low 50s by Wednesday. Pattern recognition couple with the cold pooling from the northwest flow aloft, points to the typical winter set up for fog to form. While HREF and other guidance suggests low potential for fog Sunday (10-30% chances) we can not rule out the potential for fog to form in the prone areas through the week and with cooler temperatures, chances of freezing fog is likely. However, timing on if and when fog will develop is low/moderate at best (30-50% confidence) By Thursday models show an upper level low sweeping southward of the region and breaking down the ridge. Southwesterly flow aloft will bring in warm air advection and moisture back to the region. Models show that temperatures will steadily increase Thursday through the weekend bring the area back into 5-10 degrees above seasonal average. Raw ensembles show the vast majority of the region to begin seeing temperature in the upper 30s to low 40s by the weekend. 90 && .AVIATION...12Z TAFs...VFR conditions expected to persist through the period. DLS will see MVFR over the next few hours sue to low CIGs of BKN025. How long these low CIGs will linger is difficult to pinpoint and confidence as to when they will clear out is low (10- 30%) Winds will be mostly diurnally driven below 6kts with CIGs 5kft and above. 90 && .PRELIMINARY POINT TEMPS/POPS... PDT 37 24 36 22 / 10 0 0 0 ALW 36 26 35 25 / 0 0 0 0 PSC 37 23 36 22 / 0 0 0 0 YKM 36 23 36 21 / 0 0 0 0 HRI 37 24 35 22 / 0 0 0 0 ELN 31 21 32 21 / 0 10 0 0 RDM 40 21 43 20 / 0 0 0 0 LGD 36 23 39 26 / 0 0 0 0 GCD 38 23 43 25 / 0 0 0 0 DLS 41 29 38 27 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ DISCUSSION...90 AVIATION...90

999 FXUS65 KREV 280936 AFDREV Area Forecast Discussion National Weather Service Reno NV 136 AM PST Sun Dec 28 2025 .KEY MESSAGES... * Much colder temperatures and dry weather prevails this weekend with potential for freezing fog in the Sierra. * Quiet weather with morning inversions leading to air stagnation is expected next week over western NV valleys. * There is potential for the next storm system on New Years Day through next weekend, but the system looks weak compared to the last one. && .DISCUSSION... As of 1 AM this morning, a cold and dry airmass is firmly entrenched across the Great Basin, with an upper ridge building from the west. Satellite imagery indicates mostly clear skies along with high clouds moving in from the north, but freezing fog (FZFG) is reported near Truckee. Conditions remain favorable for fog with a 40% chance of development. However, the high clouds may inhibit the development of fog. If it develops, it is expected to dissipate by late morning. Temperatures remain below seasonal normals through Monday. Morning lows across the Sierra will dip into the single digits to mid- teens, with western Nevada valleys in the mid-teens to mid-20s. Daytime highs today will be in the low to mid-30s for the Sierra, and upper 30s to low 40s for western NV valleys. The coldest morning is expected to be Monday, with many locations seeing similar or slightly colder lows than this morning. A gradual warming trend begins Monday afternoon as the ridge strengthens and shifts eastward. Winds will remain light across the entire area through Tuesday. This, combined with clear skies and cold mornings, will lead to strong valley inversions in western NV. The upper ridge breaks down by New Year`s Day as Pacific storm systems approach the West Coast. Late on New Year`s Day (Wednesday night/Thursday) marks the return of precipitation. NBM guidance shows PoPs increasing to 30-60% for the Sierra/NE CA, and 10-20% for western NV valleys. Snow levels start relatively high, between 7-8 kft, meaning lower elevations will likely see rain. Snow levels gradually lower through Friday and Saturday, increasing snow chances for passes and potentially Sierra communities. Precip chances continue through Friday and Saturday. Model guidance, including the NBM and GFS/ECMWF ensembles, shows increasing agreement on the arrival of precipitation for the New Year; although timing, intensity, and snow levels still exhibit considerable spread. We will continue to monitor model trends to refine precipitation timing, amounts, and snow levels. -HC && .AVIATION... VFR conditions prevail for much of the region over the next 24 hours, with light winds and FEW to SCT mid to high level clouds. Another round of FZFG is possible for Sierra valleys between 08-17Z this morning and tomorrow morning, bringing likely IFR/LIFR impacts to KTRK and potentially KTVL. While there is currently a 40-50% probability of FZFG, the development may be inhibited by an increase of cloud cover this morning. -Johnston/HC && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

589 FXUS66 KSTO 271859 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 1059 AM PST Sat Dec 27 2025 For additional details on weather and expected impacts over the next 7 days, please visit weather.gov/sto/briefing. .KEY MESSAGES... - Next chance of rain and mountain snow looks to be New Years Day. Confidence not very high right now with intensity but worst case sceneario would be much less impactful then recent storms. - Fog/low clouds possible in the Valley/foothills once again this week leading up to the next weather system. && .DISCUSSION... ...Tonight through Wednesday... Norhterly winds over the area as storm system which brought us all our winds/rain and snow moves out of the area. High confidence of a ridge that build into the area starting tomorrow...likely peaking in strength Tuesday with axis of the ridge shifting to our east by Wednesday. This pattern looks very simliliar to earlier this winter when we had Tule fog in the valley. Short range models not hitting the fog/low clouds very high with probabilities tonight which may be from at least some dry northerly surface winds across the valley. As the ridge strengthens early next week would expect valley fog and low clouds to occur again. This will likely keep temperatures lower again in the valley with milder temperatures in the foothills. ...New Years Day and Friday... Interesting pattern setting up for this period with fairly big difference in solutions. Cluster analysis showing most likely pattern being a moderately deep trough setting up over the west coast. Strongest solutions are the EC Ensemble solution with the GFS right now much drier. Both models showing the main moisture source for this trough to come from the southwest U.S. with really not a tropical AR type moisture fetch. With the wetter ECS solution...this system looks to NOT be nearly as impactful as the last weeks storms. Right now, like the NBM solution of blending the 2 GEFS/ECS solutions showing rain a good shot (50-80%) across the valley New Years Eve day with the ECS wetter. Again, at worst looks like mainly a low impact system. At this time, snow levels look to be around 5000 feet with NBM probabilities maxing in the 4" range. Check back for updates with this system as it gets closer. WMR && .AVIATION... Some lingering MVFR/IFR ceilings behind the passage of the storm system today, then returning to general VFR conditions after 22Z-00Z. Surface winds out of the north around 5 to 12 kts with gusts to 15-20 kts in the Valley, with northeast to east flow in the foothills and mountains at times. Patchy MVFR/IFR/LIFR conditions between 08Z-19Z Sunday in BR/FG at TAF sites from Sacramento southward. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

958 FXUS65 KMSO 280843 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 143 AM MST Sun Dec 28 2025 .DISCUSSION... KEY MESSAGES: -Much colder temperatures Sunday morning, with many valley locations dropping into the single digits to low teens. -Building Ridge (Early Next Week): Cold and much drier conditions starting Sunday. Potential for fog and low stratus to develop. Some of the coldest air has settled over the Northern Rockies. Both today and Monday may have similar temperatures to start the day. The other key component to the forecast is rising heights, via an upper level high pressure ridge. In essence, those rising heights warms the upper atmosphere producing strong inversions. While no changes have been made to temperatures by mid-week, subsequent forecasts will likely need to make adjustments as the NBM tries to warm the valleys to fast. The indicators that will be watched for the development of strong cold pools are the development and expansion of valley fog and stratus, high temperatures that cool slightly each day under the ridge, and a small range of temperatures from low to high temperature. The ridge is expected to remain in place through at least Thursday, this may keep impacts from stagnant valley air to a minimum but will be watched closely as this period evolves. How the ridge breaks down currently is uncertain as long range models have multiple equally plausible solutions. More to come in future forecasts. && .AVIATION...The coldest mornings of the season and development of high pressure will rule the forecast through Monday. Initially, fog and low stratus will be low probability at area terminals. Each day through Wednesday it is expected this impact will increase in both area and longevity. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

470 FXUS65 KBOI 280947 AFDBOI Area Forecast Discussion National Weather Service Boise ID 247 AM MST Sun Dec 28 2025 .SHORT TERM...Today through Tuesday night...Cold northwesterly flow aloft continues today as an upper level ridge axis builds to the west. This will keep temperatures below normal across the area for one more day. The upper level ridge moves over the Intermountain West on Monday and will remain the dominant feature through the rest of the short term period. This pattern will bring dry and stable conditions to the region. As the ridge strengthens, strong temperature inversions will develop and intensify. This will result in stagnant air in the valleys of southwest Idaho and southeast Oregon. An Air Stagnation Advisory is in effect and continues through the week due to the expected poor mixing heights and light winds. While mountain locations will experience mostly sunny skies and temperatures warming to 5 to 10 degrees above normal, the valleys will remain cooler under the inversion. Patchy fog and low stratus are likely to develop during the late night and morning hours in the favored sheltered valleys, potentially suppressing daytime highs in those areas. Winds will remain generally light and terrain driven, though typical drainage flows are expected overnight. .LONG TERM...Wednesday through Sunday...The upper level ridge will maintain its influence early in the long term period, keeping conditions dry and stable with valley inversions persisting through at least early Thursday. By late Thursday, the ridge is forecast to shift eastward as a Pacific trough approaches the West Coast. This system will direct a plume of subtropical moisture northward into our area, increasing precipitation chances late Thursday into Friday. Models indicate a transition to a more active pattern to close out the week. Widespread precipitation is likely Friday as the trough and associated frontal system move inland. Snow levels are expected to be relatively high initially, ranging from 4000 to 6000 feet, owing to the mild southwest flow ahead of the trough. This will result in rain for most valley locations and snow restricted to the mountains. Cooler air will arrive behind the front, likely lowering snow levels to around 3500 feet by Saturday. Precipitation chances look to decrease gradually on Sunday as the main trough axis passes to the east, though scattered showers may linger in the mountains. Temperatures will average above normal through the period, cooling closer to seasonal normals by the weekend. && .AVIATION...Mainly VFR. Brief mountain obscuration and MVFR/IFR conditions in snow showers near KBKE this morning. Surface winds: SW- NW 5-15 kt, strongest in the Magic Valley. Winds aloft at 10kft MSL: NW 20-35 kt. KBOI...VFR with high clouds. Surface winds: W-NW 4-7 kt. && .AIR STAGNATION...An upper level ridge building over the region Monday will create strong temperature inversions and light winds. This will lead to deteriorating air quality and stagnation issues in the valleys of southwest Idaho and southeast Oregon. Mixing heights will be very low starting Monday and persisting through at least Thursday. An Air Stagnation Advisory is in effect for most valley locations through the week. Conditions may improve late Thursday or Friday as the approaching Pacific system increases mixing. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Air Stagnation Advisory from 6 PM this evening to 10 AM MST Thursday IDZ012-014-016-028-033. OR...Air Stagnation Advisory from 6 PM MST /5 PM PST/ this evening to 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 SHORT TERM...JDS LONG TERM....JDS AVIATION.....JDS AIR STAGNATION...JDS

635 FXUS65 KLKN 280808 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1208 AM PST Sun Dec 28 2025 .KEY MESSAGES... Updated at 1205 AM PST Sun Dec 28 2025 * Cooler temperatures are expected today and Monday with gradually warming conditions by the mid-week portion * Winds will generally remain light through the week * Precipitation chances return to the area by the end of this week && .UPDATE... Issued at 1205 AM PST Sun Dec 28 2025 Current forecast is on track this morning. Quiet weather will continue through today with temperatures a few degrees near seasonal normals. && .DISCUSSION... (This evening through next Friday) WEATHER PATTERN OVERVIEW: A quieter weather pattern is settling into the Silver State as the late week system and associated ULT that brought a multitude of precipitation types and even some thunder to the area retreats to the east. By tonight the trough will be to the east-southeast with ridging building into the Great Basin. Clearing skies and light winds will help drop overnight temperatures into the 20s across northern NV leading to the potential for areas of fog before sunrise. Behind the trough and in the eastern flank of the ridge northerly flow will reside in the profile overhead through Tuesday. This will keep temperatures near seasonal values into the work week. A shortwave riding the ridged flow will traverse across the state on Sunday though a lack of significant forcing and efficient moisture will render nothing more than some cloudy skies for the region. The ridge pushes through the Great Basin by Wednesday and makes way for the next potential weather maker later in the week. An amplifying trough off the West Coast will begin to encroach on the CONUS by Thursday evening. A shortwave riding the parent trough will return moisture and precipitation chances to the area beginning Thursday night into Friday morning. Initially precipitation will initiate over central NV and slowly spread north through Friday. A mix of rain and perhaps some valley snow is possible with this system under a colder regime though its a bit early to speculate on amounts and accumulations. A tightening gradient and strengthening jet in the downstream of the parent trough will enhance southerly flow over the area Friday evening and Saturday increasing surface wind speeds at that time. The larger, well amplified trough pushes through the Great Basin on Saturday keeping precipitation chances over the region into next weekend. FORECAST CONFIDENCE & DEVIATIONS: High confidence continues for breezy conditions across NE NV this afternoon and cooler temperatures into next week. Low confidence remains for precipitation chances, amounts, and timing related to incoming system late next week. && .AVIATION... VFR conditions are primarily expected at all terminals through Sunday afternoon. CIGs have lifted across the region today and should remain at or above 3000FT at all terminals through the period. Saturday afternoon breezes out of the west-northwest will gust between 18-25KTs but diminish after sunset. There is potential for VCFG at KWMC/KEKO/KBAM early Sunday morning under clear skies and light winds at that time could lead to intermittent MVFR and IFR conditions. FG that does develop will burn off by mid morning on Sunday. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...86/99 AVIATION...99