990 FXUS66 KSEW 171704 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 904 AM PST Sat Jan 17 2026 .UPDATE... Clear skies over a majority of the area this morning. Some patchy fog hanging on over the Southwest Interior and north of the San Juans will dissipate by noon. Nothing new in the first look at the 12z model run with the high amplitude upper level ridge offshore and dry northerly flow aloft over the area the next few days. No updates this morning. Felton && .SYNOPSIS... A strong and stable ridge will remain in place through the middle of next week. && .SHORT TERM /TODAY THROUGH MONDAY/... Strong high pressure remains in place leading to ongoing dry and stable weather conditions. Less clouds this morning with cooler temps in the 30s. Expect highs around 50. We`ll see similar conditions through Monday. 33 && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... High pressure keeps western WA dry through at least Wednesday (and possibly Thursday). Rain/snow chances increase toward Friday and the weekend as weak disturbances pass through in NW flow. The air mass will be cooler with lower snow levels. Probabilities of lowland snow (1" or greater) are less than 10%. 33 && .AVIATION... Clear skies early this morning at the majority of the terminals. Only a few patches of fog across the terminals this morning (primarily affecting KOLM to KCLS and portions of the north interior around KAWO) - expect a mix-out later this morning into the early afternoon. The VFR conditions will persist through the day with light N/NE winds 5-10 kt. There is a 20% chance of IFR/LIFR conditions possible Saturday night, especially with lighter winds and another inversion with light flow aloft playing part to the risk. KSEA...Patchy vicinity fog remains a no-factor for visibilities at the terminal, and will burn off quick this morning with clear skies rest of the day. N/NE winds 5-10 kt. Another low chance of IFR/LIFR (20%) exists for Sunday morning with winds/gradients becoming lighter tonight. Probabilities are higher however to the north and south of the terminal as of update. 29/HPR && .MARINE... High pressure and generally light offshore winds through the weekend and early next week. 33 && .HYDROLOGY... No river flooding is expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

421 FXUS66 KPQR 171706 AFDPQR Area Forecast Discussion National Weather Service Portland OR 906 AM PST Sat Jan 17 2026 Updated Aviation discussion and Watches/Warnings/Advisories. && .SYNOPSIS...High pressure sits across the region into at least the middle of next week with dry weather prevailing. Gusty easterly winds continue through the Cascade and Coast Range gaps, and along the Columbia River Gorge into portions of the Portland metro this weekend as well, strongest today. Expect overnight/morning low stratus and fog to remain limited to valley areas more protected from east winds like the southern Willamette Valley this morning before coverage gradually increases day to day going forward due to a decrease in offshore winds. Overnight lows near/below freezing in combination with any fog may lead to locally slick road conditions - something to keep in mind. && .UPDATE...As of 0900 AM PST, areas of dense fog in the southern Willamette Valley have begun to erode as winds and insolation increase this morning. While the most sheltered valleys, including along I-5 in the Creswell/Cottage Grove area, may continue to see restricted visibility in the coming few hours, the Dense Fog Advisory has been cancelled as the majority of the region has seen visibilities rise above 1/4 mile. -36 .DISCUSSION...Saturday morning through Friday...Satellite imagery early around 2 AM PST Saturday morning indicates mostly clear skies over NW Oregon and SW Washington except for pockets of fog and low stratus in the Lane County lowlands, SW Washington lowlands (I-5 corridor), and the Upper Hood River Valley. Not expecting much more of an expansion of fog/stratus over the morning hours as current dew point depressions across much of the Willamette Valley are too wide due to drying northerly winds. Strong high pressure continues over the region through at least Tuesday, promoting a strong subsidence inversion and radiational cooling in the lowlands. Daytime temperature forecasts remain above normal for January, peaking in the upper 40s to low 50s across the Willamette Valley and upper 50s to 60s along the coast and western foothills of the Coast Range and Cascades. Additionally, morning low temperatures will be near or below freezing across low lying areas that are away from easterly winds from the Gorge, leading to the promotion of widespread frost in these areas. However, elevations around ~1000-5000 ft will see much warmer than normal low temperatures due to the strong subsidence inversion. The main hazard of concerns remains the east winds through the western Columbia River Gorge. A thermally induced trough at the surface remains situated just over the Oregon and Washington coast, leading to a strong surface pressure gradient over the Cascades. Current observations show a -9 to -10 mb pressure gradient between KPDX and KDLS, which is expected to continue through much of today. This is resulting in peak wind gusts up to 40-55 mph into the Troutdale area, 25-45 mph in the eastern Portland metro, and 55-70 mph for our climatologically windiest spots like Corbett, Crown Point, Three Corner Rock, etc. A Wind Advisory remains in effect through this afternoon for the eastern Portland metro area. Breezier east winds with peak gusts up to 35-45 mph are also expected through some Coast Range gaps and peaks of the Coast Range and Cascades. Most ensemble guidance indicates the pressure gradient begins to slowly weaken tonight into Sunday as the ridge weakens slightly causing the thermal trough near the surface to also weaken. Breezy winds are still expected into Sunday and early next week, just not as strong as yesterday and today. Elevated east winds are likely to continue in the Gorge into at least Wednesday, but not expecting much more than peak gusts up to 25-30 mph making it farther west than the Troutdale area beyond Sunday. As the thermal trough weakens and strong easterly winds diminish outside of the Gorge, fog chances increase each night and morning, becoming more widespread across the interior lowlands. Overnight lows near or below freezing in combination with any fog may lead to locally slick road conditions. Additionally, stagnant air is increasingly a concern under this subsidence inversion as the winds decrease, leading to air quality concerns today into at least Tuesday. An Air Stagnation Advisory is in effect for most of the Willamette Valley due to this concern. Beyond Tuesday, ensemble guidance indicates the strong high pressure will begin breaking down with ~75% of the GFS, Euro, and Canadian ensemble members indicating lowering 500mb heights over Oregon and Washington on Wednesday. However, the magnitude of lowering heights is not as strong as previous guidance, and the precipitation chances have been mainly eliminated on Wednesday. The main impact from the breakdown of the high pressure is the subsidence inversion beginning to break down along with temperatures beginning a return to near normal for January. By Thursday, nearly all ensemble members are on board with the breakdown of the high pressure, though not with the return of precipitation. There`s around a 15-30% chance of precipitation returning sometime Thursday, mainly over the coast and terrain. Precipitation chances increase Friday to 20-40% chance for the interior lowlands and 30-55% for the coast and terrain. One thing to note is overnight temperatures will remain on the cold side across most of the area, and a colder airmass will remain in place near the surface around Hood River valley and surrounding areas. This along the lingering easterly flow through the Cascade gaps could lead to a period of wintry precipitation as precipitation begins for lower elevations, mainly in the Columbia River Gorge, Hood River Valley, and surrounding locations. Specific details will become more clear as we get closer to precipitation returning. -03 && .AVIATION...A persistent upper level ridge over the region will continue to yield widespread VFR conditions for most terminals through the period. Fog or low stratus will continue in sheltered portions of the Cowlitz and southern Willamette Valleys through 20-21z Sat, although major terminals including KEUG have already cleared out this morning. Ongoing offshore flow will maintain east winds in the Portland area as well as along the coast, with northerly flow expected through the Willamette Valley. The gustiest east winds will be constrained to the western Columbia River Gorge including near KTTD where gusts of 35-45 kt are likely to continue through the period, up to 50-55 kts east of KTTD. Gap flows through the Coast Range will also yield areas of gusty east winds at favored locations along the coast, including near KONP. Where surface winds are sheltered from stronger easterlies to the west of the Columbia River Gorge, low-level wind shear of 35-40 kt in the lowest 2 kft will continue. KPDX AND APPROACHES...VFR flying conditions with largely clear skies through the period. East-southeast winds will increase to 10-15 kt with gusts up to 25 kt by 20-21z Sat, then easing again to around 10 kt or less after 00-03z Sun. -36 && .MARINE...Strong upper level high pressure continues into the weekend with a thermally-induced surface trough along the coast favoring persistent easterly offshore flow. While winds are largely at 10 kt or less, areas downwind of gaps in the coastal terrain may see stronger flow with gusts as high as 20-25 kt. The most widespread area of these stronger gusts continues west of the mouth of the Columbia River, between Cape Foulweather and Cape Falcon beyond 10 NM, where a Small Craft Advisory has been extended through 10 AM this morning. East winds otherwise persist through the weekend, generally less than 15-20 kt. Seas remain below 10 ft around 10-13 seconds through early next week. -03/36 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory from 7 PM this evening to 10 AM PST Tuesday for ORZ109-114>118. Wind Advisory until 3 PM PST this afternoon for ORZ112. WA...None. PZ...Small Craft Advisory until 10 AM PST this morning for PZZ271. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

778 FXUS66 KMFR 171759 AFDMFR Area Forecast Discussion National Weather Service Medford OR 1000 AM PST Sat Jan 17 2026 ...Updated AVIATION discussion for 18Z TAFs... .DISCUSSION...Satellite shows the Illinois Valley and Umpqua Basin have low clouds/fog as of 3 AM. The Rogue Valley warmed up more today, but RH`s are nearing 100% now, so looking for fog development early this morning. A Freezing Fog Advisory is in effect through the morning for the Illinois Valley. Please remember that anywhere that has freezing fog could have icy surfaces. Skies are clear otherwise. Once again, the ridge of high pressure will hold the weather pattern of strong inversions and stagnant air that leads to evening/overnight fog for west side valleys for the next several days. Warmer temperatures at the coast in the upper 50s to low 60s will be found this weekend. Upper 40s/ low 50s will be found east of the Cascades. Even if there is clearing this afternoon, fog will quickly return to the same spots this evening. High pressure is forecast to remain in control for the next several days, although there could be a disturbance that finally reaches the western US next weekend. Other than that, there will be dry conditions everywhere and fog in west side valleys. -Hermansen && .AVIATION...17/18Z TAFs...Fog remains in the Umpqua and Illinois Valleys as well as parts of the Rogue Valley. Fog is expected to decrease through the morning, with VFR levels across the area possible later in the afternoon. With stable conditions persisting, fog is expected to return to these same areas this evening into early Sunday morning. -TAD && .MARINE...Updated 300 AM PST Saturday, January 17, 2026....Seas remain below Advisory level through the weekend. Northerly winds look to increase on Monday, which may build localized areas of steep seas in outer waters. Winds look to ease into Tuesday and Wednesday. -TAD/Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 10 AM PST Tuesday for ORZ023-024- 026-029>031. Freezing Fog Advisory until noon PST today for ORZ024. CA...None. PACIFIC COASTAL WATERS...None. && $$

764 FXUS66 KEKA 170807 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1207 AM PST Sat Jan 17 2026 .SYNOPSIS...High pressure is forecast to remain over NW California through the weekend resulting in dry weather and generally above normal daytime temperatures. Overnight and morning temperatures will remain chilly with night and morning fog in river valleys. && .DISCUSSION...An upper level ridge has situated itself over the West Coast leading to large scale subsidence and adiabatic warming. Anomalous interior warmth with temperatures above climatological norms will continue under the strong ridge. With clear skies and exceptional longwave cooling, it will continue to remain cold in the river valleys each night and morning, especially in northern Humboldt, Trinity and northern Mendo through the end of this week. The ridge aloft will continue to provide dry and stable weather conditions for NW California through the weekend. The anomalous interior January warmth is contributing to a strong inverted trough and elevated northeasterly winds, especially over the ridges. Early Saturday morning, satellite indicates a stratus deck approaching Northwest California, particularly close to the Mendocino coast. However,the offshore flow is greatly reducing the chances for coastal stratus and fog to make it onshore. Chances for the ridge to weaken or breakdown do not increase until the middle of this coming week. Probabilities for meaningful rainfall over 0.1 inch do not increase until late next week and next weekend. After another prolonged stretch of dry weather, wet weather will likely return for the latter part of January for NW CA. && .AVIATION...The stratus remains off the Mendocino coast this morning. Any vis/cig reductions at KACV and KCEC look like they will be locally generated this morning. Confidence is low on whether this will form and if it does it will likely be intermittent. The offshore flow looks to keep stratus away through most of the daylight hours on Saturday. There is more confidence in the stratus making it onshore Saturday late in the afternoon and evening. Inland the northern valleys that have been seeing fog will likely see it this morning. KUKI will likely remain clear again as well. Winds will generally be light, aside from the easterly winds over the higher terrain. MKK && .MARINE...Northerly winds remain around 5 to 10 kt with some very light wind chop. These winds are expected through Sunday morning. Waves have dropped to 4 to 5 feet and these are expected to continue through Sunday morning. Sunday afternoon or Sunday night northerly winds winds are expected to return and increase to 15 to 20 kt on Monday. There are still some differences in the models on how strong these will get, but most models keep them below 20 kt. These winds are shortlived and expected to diminish by Tuesday. Monday night and Tuesday the GFS wave model is showing a long period wave moving in and building to around 5 to 6 feet. MKK && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... None. && $$ 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

336 FXUS66 KMTR 172041 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1241 PM PST Sat Jan 17 2026 ...New SHORT TERM, LONG TERM... .KEY MESSAGES... Updated at 1240 PM PST Sat Jan 17 2026 - Dry weather, cool mornings, and warm afternoons persist into early in the week - Morning fog across the delta and interior North and East Bay Valleys && .SHORT TERM... Issued at 1240 PM PST Sat Jan 17 2026 (This evening through Sunday) Not much change this afternoon, similar to yesterday with fog lingering in the interior East Bay Valleys and the West Delta. The most notable difference, is that we have high clouds moving from south to north across the region. We will continue to watch closely how these high clouds will affect afternoon temperatures, but largely should still be another warm day across much of the region this afternoon with high temperatures in the mid 60s to mid 70s (up to 80 degrees F in the higher terrain). Tonight, look for fog (dense at times) to develop across the West Delta, North Bay Valleys, and interior East Bay Valleys that will linger into Sunday morning. Again, high clouds may limit overnight cooling by a few degrees making the fog forecast difficult. Offshore winds are forecast to decrease over the next 36 hours or so, and may allow for more cooling in the higher elevation tonight. Looking for a near repeat for Sunday afternoon as high clouds will continue to stream across the region. Thus, temperatures will be similar to Saturday afternoon. && .LONG TERM... Issued at 1240 PM PST Sat Jan 17 2026 (Sunday night through next Friday) Little change in the long term forecast as a mid/upper level ridge of high pressure will remain in place just off of the West Coast through midweek. Thus, look for similar conditions as this weekend to persist. Late night and early morning fog across the West Delta, North Bay Valleys, and interior East Bay Valleys looks like a good possibility. By late week, there is a potential weak short wave trough forecast to impact the region with chances for light rainfall Friday into Saturday. However, it is looking the region may just see an increase in cloud cover and return of cooler conditions (closer to seasonal averages). It isn`t until late January we see the Climate Prediction Center show the region leaning above normal in their 8-14 Day Precipitation Outlook. && .AVIATION... (18Z TAFS) Issued at 902 AM PST Sat Jan 17 2026 Stratus is clearing out across the interior East Bay valleys as the Tule Fog starts to mix out across the Central Valley. The far interior could remain socked in through the day but CCR should clear out later this morning and afternoon. Generally VFR conditions with high level clouds prevail through the day elsewhere, with predominantly gentle winds and a largely offshore flow across the interior, with a gentle onshore breeze for the coastal areas. Overnight, radiational fog develops across the North Bay valleys, including STS and APC, and the East Bay valleys, although confidence is low for impacts at LVK, CCR has a better chance for reduced visibilities and lowered ceilings overnight. High resolution models are also placing some possibility for fog or low stratus at SJC later tonight, but this is a low confidence forecast at this time. Vicinity of SFO... VFR through the TAF period. A gentle offshore flow develops in the afternoon and evening hours. Otherwise, winds remain light and variable. SFO Bridge Approach... Similar to SFO. Monterey Bay Terminals... VFR through the TAF period. Light and variable winds through the daytime, with breezy valley drainage winds developing overnight. && .MARINE... (Today through Thursday) Issued at 837 AM PST Sat Jan 17 2026 Moderate to breezy northeast winds continue across the San Pablo Bay, the delta, and through the Golden Gate through the weekend while light northeast to north winds persist across the rest of the coastal waters. Light seas continue into early next week before the next round of long period swell arrives and brings light to moderate seas in the mid week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...None. PZ...None. && $$ SHORT TERM...RGass LONG TERM....RGass AVIATION...DialH MARINE...DialH 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

638 FXUS66 KOTX 171811 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 1011 AM PST Sat Jan 17 2026 .KEY MESSAGES... - Dry and stagnant pattern under strong ridge of high pressure through Tuesday. - Areas of low clouds and dense fog to continue through the weekend and into early next week. && .SYNOPSIS... Strong high pressure will remain in place through at least Tuesday. In the meantime, low clouds and fog are expected to impact the lowlands through early next week. Confidence is low on coverage and timing of low cloud and fog coverage. There is an increasing signal for unsettled conditions to return by the middle-to-later stages of next week. && .DISCUSSION... Today through Monday: The persistent ridge is is still positioned of the coast and continue to create stable and stagnant conditions for the Inland Northwest. Stratus and fog continue to be impact locations across the Basin and in the valleys. The higher terrain across the region. The models are in good agreement on the stubbornness of the ridge. Areas along the edges, particularly near the Cascades could see some breaks in the stratus during the afternoon hours. Highs will continue to be in the 30s for most with of the edge locations reaching into the low 40s. Tuesday through Saturday: Ensembles are beginning to show a change in the upper level pattern starting Tuesday. The region becomes wedged between high over the Pacific and strengthening Low over Manitoba. It will allow a strong North to South flow pattern and bring a series of shortwaves and cold Arctic air into the region. The first wave on is expected to glance the Idaho Panhandle. Ensembles have been shifting it eastward. Light snow showers with little to no snow accumulation expected through Wednesday. The next wave is expected late Thursday into Friday. This is one to watch. While it is several days out, ensembles are hinting at decent mountain snow amounts and possible low land impacts. Highs will be in the low 30s and 20s. Lows will upper teens and 20s. /JDC && .AVIATION... 18Z TAFs: Persistent and widespread low stratus will continue through the TAF period, with primarily MVFR/IFR conditions. Expect stratus cover to slosh around a bit, but continue to have a presence over the Inland Northwest through the weekend. Recent observations and trends have heavily shaped the forecast with models continuing to have a poor handle on conditions. Winds will remain light and variable at most sites. If any sites on the edge of the stratus are able to break out this afternoon, expect stratus/fog to fill back in tonight. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence is areas of persistent low stratus to continue. Low confidence on specific locations of fog development. ----------------------- 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 36 24 37 24 36 24 / 0 0 0 0 0 0 Coeur d`Alene 38 24 38 22 37 24 / 0 0 0 0 0 0 Pullman 40 26 38 26 38 27 / 0 0 0 0 0 0 Lewiston 41 29 40 27 40 28 / 0 0 0 0 0 0 Colville 37 22 38 21 37 23 / 0 0 0 0 0 0 Sandpoint 36 25 37 22 35 25 / 0 0 0 0 0 0 Kellogg 40 29 39 24 39 27 / 0 0 0 0 0 0 Moses Lake 37 25 38 24 37 25 / 0 0 0 0 0 0 Wenatchee 37 29 40 29 38 28 / 0 0 0 0 0 0 Omak 38 26 38 25 37 25 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...Air Stagnation Advisory until 4 PM PST Tuesday for Central Chelan County-Moses Lake Area-Northeast Mountains- Okanogan Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin-Waterville Plateau-Wenatchee Area-Western Chelan County-Western Okanogan County. ID...Air Stagnation Advisory until 4 PM PST Tuesday for Central Panhandle Mountains-Coeur d`Alene Area-Lewis and Southern Nez Perce Counties-Lewiston Area-Northern Panhandle. && $$

625 FXUS66 KPDT 171747 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 947 AM PST Sat Jan 17 2026 .AVIATION UPDATE. .AVIATION...18Z TAFs...Stratus across the area continues to influence weather across the sites with MVFR to LIFR conditions now and through out the TAF period. Expect fog in the Central Oregon zones to continue for the next few hours, but we`ll a redevelopment of fog across most sites through tomorrow morning. Low stratus will continue to either bring at least one of low visibility from fog or low stratus deck CIGs through the next 24 hours. Otherwise, winds remain light and mostly variable across the region. && .PREV DISCUSSION... /issued 330 AM PST Sat Jan 17 2026/ DISCUSSION...An upper level ridge impacting the region continues to support an extensive stratus layer from the Upper Columbia Basin down into Central OR and the John Day Basin. Most areas that have been under the stratus layer the past several days have seen dense fog lift, however visibilities less than half a mile persist in the Kittitas valley. Meanwhile, elevated areas of central and north central OR continue to see impacts from freezing fog, with visibilities a half mile or less as well. Other than fog/stratus, the only notable ongoings across the forecast area is an area of fine, light snow that has developed in an area between Walla Walla, Pendleton, and Cold Springs. At present, most surfaces are warm enough to prevent any accumulation, though a dusting is possible on the top of cars. The stratus layer and inversion just above it will persist into the middle of next week as the PacNW stays under the influence of the upper ridge offshore. Uncertainty still remains around the redevelopment and strength of fog in areas around the Yakima Valley and Walla Walla the remainder of tonight. Otherwise, as the days progress, the chances of fog redeveloping steadily decreases across the remainder of the Columbia Basin and adjacent areas. For now though, have kept mention of patchy fog across areas under the stratus layer through Monday morning. By Tuesday night, ensemble guidance is in good agreement in the upper ridge beginning to erode away as a trough dives down the continental divide. This will weaken the impacts from the upper ridge over the region, providing an opportunity to break the inversion/stratus layer over the inland PacNW Tuesday night into Wednesday, though conditions will remain for the better part dry across the forecast area. Late Wednesday into Friday, ensemble guidance is in decent agreement of troughing beginning to develop over the region, however there is great disagreement on the strength of the incoming trough, resulting in low confidence (10-20%) in precipitation amounts and type Thursday onward. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 34 25 34 23 / 10 0 0 0 ALW 35 29 34 25 / 10 0 0 0 PSC 38 27 36 25 / 0 0 0 0 YKM 35 27 38 24 / 0 0 0 0 HRI 35 26 35 24 / 0 0 0 0 ELN 35 26 37 23 / 0 0 0 0 RDM 37 23 42 19 / 0 0 0 0 LGD 46 31 47 25 / 0 0 0 0 GCD 52 32 52 28 / 0 0 0 0 DLS 40 30 40 27 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Air Stagnation Advisory until 4 PM PST Tuesday for ORZ041-044- 507-508-510-511. Freezing Fog Advisory until noon PST today for ORZ510-511. WA...Air Stagnation Advisory until 4 PM PST Tuesday for WAZ024- 026>029-521. Freezing Fog Advisory until noon PST today for WAZ026. && $$ SHORT TERM...82 LONG TERM....82 AVIATION...95

107 FXUS65 KREV 172059 AFDREV Area Forecast Discussion National Weather Service Reno NV 1259 PM PST Sat Jan 17 2026 .KEY MESSAGES... * Light winds and valley inversions will keep hazy skies and air quality reductions through this weekend with patchy freezing fog in some Sierra valleys. * Dry weather prevails through this weekend into next week with above average daytime temperatures and slightly below average low temperatures. && .DISCUSSION... * I will keep this discussion short because there is still not much to talk about at the moment. An amplified high pressure ridge remains parked over the eastern Pacific and the western US. Model ensembles keep this ridge pattern through at least Wednesday. By Thursday, the aforementioned ridge begins to retrograde west into Alaska while an upper low currently across eastern Canada expands westward as well. Toward the end of next week, the ensembles start to diverge in their solutions. Some show weak ridging while others show a trough dropping southward over the west. * Weather-wise, we`ll hang on to our quiet pattern through Wednesday. Strong inversions will keep the overnight low temperatures below average high temperatures stay above average. The inversions will also maintain stratus and freezing fog over Mono Lake, and Martis Valley in the morning. By Thursday into next week, the pattern will change. Blended guidance has introduced a low 20% chance for precipitation. However, confidence is low. That`s all I have for you today. -McKellar && .AVIATION... VFR conditions are expected for area TAF sites going through the holiday weekend. The only exception is at KTRK where patchy and mainly shallow FZFG is expected through this morning around 14Z and then again tonight into Sunday morning. Haze in W.NV may lead to reduced slantwise visibilities. -078/McKellar && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

255 FXUS66 KSTO 171310 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 510 AM PST Sat Jan 17 2026 .KEY MESSAGES... - Dense fog this morning in the Valley and Delta - Dry weather expected next 7 days with a return to widespread Valley fog/low clouds and warm/dry weather at higher elevations. - High uncertainty for very light mountain precipitation late next week. && .UPDATE DISCUSSION... A Dense Fog Advisory has been issued through 10 am this morning for the southern Sacramento Valley, Delta and northern San Joaquin Valley due to widespread dens fog developing, particularly near the Sacramento and San Joaquin rivers and the Delta. Use caution driving, giving yourself extra time for driving this morning. Use low beam headlights and allow extra space between you and the vehicle in front of you. .PREVIOUS DISCUSSION... ...Today Through Mid-Week... Dry weather continues across the area as ridging remains in place, with chances for patchy to dense fog and low clouds expected over the next several days. Lingering low clouds persist across portions of the Delta and northern San Joaquin Valley early this afternoon, but are expected to dissipate over the next couple of hours. HREF guidance shows a 40 to 70 percent chance of visibility reductions below a half mile overnight and into Saturday morning across the Delta, portions of the central and southern Sacramento Valley, and northern San Joaquin Valley; highest chances over the southern Sacramento and northern San Joaquin valleys. Valley highs will be in the low 60s to mid 70s this afternoon, before lowering slightly over the weekend. Highest temperatures still expected in the northern Sacramento Valley and the foothills. Breezy winds are expected at times over the mountains and foothills during the overnight and early morning hours. ...Mid-Week Through Late Next Week... Ensembles show a flattening of the ridge later next week, bringing slightly cooler temperatures and a slight potential for very light precipitation over the mountains. Not expecting anything impactful as there is currently a 10-25% probability of precipitation greater than 0.1 inches over the mountains late next week. Temperatures are expected to cool slightly, with Valley temperatures generally in the upper 50s to low 60s. Chances for morning fog and low clouds continue through the period. && .AVIATION... Lingering IFR/LIFR conditions in central/southern Sacramento Valley, Delta, and northern San Joaquin Valley this morning through 20z. FG/BR expected to develop around 05z Saturday with similar aerial extent to this morning. Surface winds below 12 kts in the lower elevations, with E-NE wind gusts of 25 kts in the Sierra and Southern Cascades. && .STO WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM PST this morning for Carquinez Strait and Delta-Northern San Joaquin Valley-Southern Sacramento Valley. && $$

314 FXUS65 KMSO 172024 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 124 PM MST Sat Jan 17 2026 .DISCUSSION... KEY MESSAGES: - High pressure will keep above-normal temperatures in the forecast through midweek - Pattern change later in the week (next Friday - Saturday), bringing colder temperatures and snow Visible satellite imagery this afternoon shows mostly clear skies across the Northern Rockies under high pressure with some notable exceptions. Strong inversions are keeping low stratus decks and, in some cases, reduced visibility due to fog across the valleys of Lincoln, Sanders, and Lake counties in Montana; and the Upper Salmon/Lemhi, Lower Salmon, and Lower Clearwater valleys in Idaho. Little pressure gradient to drive surface winds should keep these inversions in place through Sunday morning. A weak disturbance on Sunday night should help to break inversions that are still hanging on. Mostly mundane weather persists through much of the upcoming work week as a high amplitude ridge sets up over the West Coast. The Northern Rockies will be under northerly flow aloft on the east side of the ridge. Some opportunity for moisture arrives on Tuesday afternoon for the Continental Divide under an embedded shortwave disturbance. Chances for measurable precipitation are low as the 90th percentile of ensemble distributions is only showing a few hundredths of liquid precipitation by Wednesday morning. Ensemble solutions are trending towards a significant change starting Thursday night or Friday. Most solutions are favoring an arctic cold front breaching the Continental Divide from the east in northwest Montana on Friday. Uncertainty is stemming from the formation and position of low pressure descending south from Canada that would interact with the cold air behind the front. We`ll have a clearer picture as the week unfolds. In the meantime, please stay on top of the forecast if you have travel plans for next weekend. && .AVIATION...High pressure is keeping fog and low stratus over airfields at Salmon, Grangeville, and Ronan this afternoon. Visibility is still down below 1SM at Ronan in the Mission Valley early this afternoon. Fog has lifted at the other aforementioned terminals, but low stratus is keeping ceilings below about 400 ft AGL. Expect poor visibility and low ceilings to persist through Sunday morning at least. A weak disturbance moving north to south on Sunday evening should break the remaining valley inversions. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...ID...Air Stagnation Advisory until 4 PM PST Tuesday for Northern Clearwater Mountains...Orofino/Grangeville Region... Southern Clearwater Mountains. && $$

836 FXUS65 KBOI 172103 AFDBOI Area Forecast Discussion National Weather Service Boise ID 203 PM MST Sat Jan 17 2026 .SHORT TERM...Tonight through Monday night...The pattern remains dry and stable as an upper ridge remains over the region, blocking the storm track. The ridge is slowly moving directly overhead bringing warmer air and strengthening the inversion. This will bring continued fog, low clouds, colder temps, and reduced air quality for lower elevations. Higher terrain will see temps at or above normal with clear skies. Fog has mostly lifted to stratus today, and will likely repeat this pattern in the following afternoons with some brief clearing possible. Overnight, stratus will settle and dense fog will redevelop each morning. Although, the southeast winds we saw today should have dissipated more of the stratus deck than it did, which brings some concern for if the clouds will show any clearing in the following days where southeast winds are not forecast. .LONG TERM...Tuesday through Saturday...The ridge remains overhead with northwesterly flow through Thursday morning. This period will see continued low elevation stagnant air, fog, colder temperatures, and reduced air quality as the inversion breathes what are hopefully its final breathes. Thursday and especially Friday the pattern begins to change significantly as a deep Hudson Bay low brings arctic air over much of the US, and we move into it`s western influence. This pattern change will open the door for shortwaves and moisture to finally bring some precipitation and mixing to the stagnant and dry conditions. Right now this forecast hinges on a shortwave and the position of the low, which have yet to be solidified amongst models. Ensemble clusters still show some potential for the low`s influence to miss us. However, the strength of the low should at least bring winds to help mix out the inversion or weaken it even if the precip misses us. && .AVIATION...Low elevation fog has mostly lifted to stratus. Ceilings have not shown much dissipation, and many areas may now not see previously expected clearing. MVFR-LIFR in low stratus will continue with local improvement to VFR in slow dissipation. Fog/low stratus redevelops tonight bringing conditions back down to IFR-LIFR, with possible expansion into SE OR. Mtns remain clear. Surface winds: Variable less than 8 kt. Winds aloft at 10kft MSL: Variable 5-15 kt. KBOI...MVFR stratus will persist through the day, with a low chance of brief clearing later this afternoon. LIFR conditions return with fog/low stratus redevelopment tonight and could remain in place well into Sunday. SE winds become light and variable this afternoon. && .AIR STAGNATION...The inversion and stagnant air is expected to last through Thursday. This means mixing heights of less than 2kft MSL, light winds, and reduced air quality. Valley locations that have setup under fog/clouds will likely keep these conditions through the Tue-Thur time period (some daytime erosion and thus glimpses of the sun are possible). && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Air Stagnation Advisory until 11 AM MST Thursday IDZ011>014-016-028-033. OR...Air Stagnation Advisory until 11 AM MST /10 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...JM LONG TERM....JM AVIATION.....JM AIR STAGNATION...JM

084 FXUS65 KLKN 172000 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1200 PM PST Sat Jan 17 2026 .KEY MESSAGES... Updated at 1159 AM PST Sat Jan 17 2026 * Dry weather persists thru the next several days * High temperatures well above seasonal values each afternoon Saturday thru Thursday * A change in the weather pattern is possible late next week && .DISCUSSION... (This afternoon through next Saturday) WEATHER PATTERN OVERVIEW: Continued ridging and high pressure will keep conditions in Northeast Nevada warm and dry through midweek. Daytime temperatures will be around ten degrees warmer than normal while overnight temperatures will be near normal, in the upper 40s/low 50s and teens/20 respectively. Models are showing signs of a return to an active pattern by the end of the week but theres still a lot of uncertainty about what that will actually look like regarding precipitation potential and temperatures. FORECAST CONFIDENCE & DEVIATIONS: High forecast confidence for dry weather and above average temperatures through Wednesday. Low forecast confidence for the pattern change late week. Low temperatures tonight have been adjusted down a few degrees as NBM baseline continues to run too warm. && .AVIATION...VFR conditions and light winds continues at all sites through the next 24 hours. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...94 AVIATION...94