ZSE Aviation Forecast Discussions

421 FXUS66 KSEW 090933 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 133 AM PST Tue Dec 9 2025 .SYNOPSIS... A strong atmospheric system will continue to bring periods of heavy rain and gusty winds to western Washington through Wednesday. Widespread significant river flooding is underway and is expected to continue through much of the week. Minor coastal flooding due to astronomical high tides will also pose concerns for the northern Salish Sea coastlines through much of the week. Wet and unsettled conditions will continue through the forecast period. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/... A strong atmospheric system is well underway across western Washington this morning, bringing in widespread heavy rainfall to western Washington alongside breezy winds. The axis of moisture will continue to shift southward throughout the morning today behind a cold front with most areas northward of Chehalis seeing drier conditions, providing a brief lull in rainfall across the region. However, flooding is still expected despite a brief decrease in rainfall. Heavy precipitation will fill back in by this evening as the atmospheric river shifts northward and takes direct aim once again at western Washington. While this second wave of precipitation will not bring quite as heavy rain rates, this longer duration rainfall will keep rivers elevated across the region, and even potentially causing rivers to peak higher, with significant river flooding expected to continue over the next few days. The following key messages with this atmospheric river system are outlined below: * HEAVY RAIN: Despite a decrease in rainfall this morning, the atmospheric river system will bring another wave of heavy rain to western Washington by this evening, continuing through Wednesday night. While areas east of the Olympics will likely see some shadowing at the onset of precipitation once again this afternoon, heavy rain will continue to cause flooding concerns to area rivers, urban areas, and areas with poor drainage. Forecast models remain consistent with rainfall forecasts, showing an additional 2 to 3 inches of rain across the lowlands and 5 to 8 inches over the mountains through late Wednesday. Many area rivers have entered major flood stage, with another wave of rises expected tonight into Thursday. For more details, see the HYDROLOGY section below. * WINDS: Winds will gradually decrease this morning, with another wave of breezy winds this afternoon alongside the second wave of rainfall. Wind gusts are expected to reach 40-45 mph across the region later today as the second wave of the atmospheric river system pushes into the region. Winds will peak this evening and remain elevated into Wednesday. * COASTAL FLOODING: Minor coastal flooding remains possible today along the northern Salish Sea coastlines with high astronomical tides. While the tides will generally remain below or nearing thresholds, heightened river flows or wind effects could exacerbate inundation in some areas around high tide. In addition, snow levels will briefly lower to near 3500-4000 feet over the mountains this morning, resulting in minor accumulating snow generally above 4500 feet. The higher mountain passes, including Stevens Pass and White Pass, will likely see a few inches of snow accumulation throughout the day today which could cause brief slippery travel conditions. The returning surge of moisture later this afternoon will bring warmer temperatures and higher snow levels through the remainder of the week. Temperatures will peak well above normal most days this week, with temperatures in the low to upper 50s across the lowlands. && .LONG TERM /THURSDAY THROUGH MONDAY/... Forecast models remain in good agreement that unsettled conditions will continue through the remainder of the week and into early next week as additional systems are set to cross over the Pacific Northwest. It is likely that impacts from significant river flooding will linger through Thursday and even into the weekend for many areas. Mild conditions are favored to continue through the forecast period, with little relief from wet conditions in sight for western Washington. 15 && .AVIATION... Generally MVFR to IFR as heavy rainfall from an atmospheric river slowly shifts southward this morning. This should allow for some small improvement in ceilings and vis this morning, though conditions are expected to deteriorate once again as heavy precipitation fills in across western Washington this afternoon. North to northeast winds generally 10 to 20 kt with gusts up to 25 to 30 kt will continue to ease this morning and shift southerly by 12z. Winds will increase once again this evening, with speeds returning to 10 to 20 kt with gusts reaching 30 kt. KSEA...IFR this morning with slight improvement to MVFR this morning after 12Z. May see some brief improvement to low- end VFR conditions around 21Z, but ceilings are expected to deteriorate late Tuesday evening into the overnight hours to IFR. Southerly flow at the terminal is expected to switch NE around 06Z tonight, gusting to 25-30 kt. SW winds return after 12Z and winds will gradually subside late Tuesday morning to 5-10 kt. Winds will increase again late Tuesday evening to 10-15 kt, gusting to 20-30 kt. 29/15 && .MARINE... A strong cold front will move across area waters early this morning, with strong west winds through the Strait of Juan de Fuca and coastal waters. Winds will taper off into the late morning behind the cold front, though seas will remain elevated between 9 to 14 feet. The next system arrives late Tuesday night into Thursday, bringing moderate to heavy rain that may locally reduce visibilities at times, breezy southwest winds that may reach gale force, and elevated seas above 10 feet. Seas will ease into Friday to around 4 to 6 feet, where they will remain through much of the weekend. Another system will increase seas and winds early next week. 15 && .HYDROLOGY... A strong atmospheric atmospheric will continue to move through the Pacific Northwest through Wednesday, bringing significant heavy rainfall across the area. 72-hour precipitation amounts between Monday and ending Thursday morning will likely reach 2 to 6 inches across the lowlands, with 6 to 10 inches over the Olympics and Cascades with locally higher amounts up to 12 inches over the central and southern Cascades. Rivers continue to rise across the region, with numerous flood warnings in effect. Consult weather.gov/seattle for the latest. While some uncertainty does still remain in regards to the exact flood levels and stages through the next week, many river forecast points are projected to reach major flood stage in the days ahead. Therefore, it will be critical to monitor the forecasts now and through the next seven days. Additional precipitation is also possible Thursday and Friday, which may keep rivers elevated heading into the weekend. A Flood Watch remains in effect across all of western Washington through Friday. With the wet antecedent soil conditions, the landslide threat across the region will increase with this system. Potential has also increased for debris flows over area burn scars, which will continue to be monitored. Urban and small stream flooding, as well as areas with poor drainage, should be alert to the potential for localized nuisance flooding and ponding on roadways. Low water crossings may become impacted or impassable. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Flood Watch through Friday afternoon for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-City of Seattle-Downtown Everett / Marysville Area-Eastern Kitsap County-Eastern Strait of Juan de Fuca-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast-Island County- Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties- Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Northern Washington Coast- Olympia and Southern Puget Sound-Olympics-Port Townsend Area-San Juan County-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Western Strait of Juan de Fuca- Willapa and Black Hills. Coastal Flood Advisory from 7 AM this morning to 1 PM PST this afternoon for Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-San Juan County. PZ...Small Craft Advisory until 7 PM PST this evening for Grays Harbor Bar. Gale Warning until 4 AM PST early this morning for Admiralty Inlet-Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm- Northern Inland Waters Including The San Juan Islands- Puget Sound and Hood Canal-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 7 PM PST this evening for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca. Gale Warning until 7 AM PST this morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$

985 FXUS66 KPQR 091335 AFDPQR Area Forecast Discussion National Weather Service Portland OR 535 AM PST Tue Dec 9 2025 .SYNOPSIS... A prolonged atmospheric river continues to influence the Pacific Northwest, sustaining periods of heavy rainfall, breezy winds, and widespread hydrologic concerns through late Wednesday, possibly as late as early Thursday. Widespread river flooding remains likely, along with urban and small stream flooding due to persistent heavy rain. Wind may lead to downed trees and power outages due to saturated soils. && .DISCUSSION...Now through Sunday...Over the past 24 hours, around 4 to 7 inches of rain has fallen over the north Oregon Cascades, south Washington Cascades, Willapa Hills, north Oregon Coast Range, south Washington coast, and northern and central Oregon coast. About 1.5 to 4.5 inches of rain has fallen over the Lower Columbia, Cowlitz Valley, and Portland/Vancouver metro. Refer to the Hydrology section below for river information. As of 430 AM, precipitation has decreased along the coast but has increased inland. Around 230 AM to 330 AM, a mesoscale band of heavy rain moved southward through the Portland/Vancouver metro. Around 0.20 to 0.40 inch per hour was observed over the area during that time period, increasing urban flooding and prompting the issuance of a Flood Advisory. With this mesoscale band and increasing precipitation inland, the Flood Advisory will be maintained until 10 AM today. Attention now turns to the second moisture surge expected to arrive later this afternoon and persist into Wednesday. IVT values are projected to be around 600 to 700 kg/ms across western Washington and far northwest Oregon, suggesting the strength of the atmospheric river to remain moderate. Given past observations since Monday, we could see a stronger atmospheric river. An additional 1 to 2 inches of rain is expected this morning through Thursday afternoon over the interior lowlands to the north of Eugene. Around 3.5 to 6.5 inches of additional rain is expected over the Cascades and coastal mountains, mainly to the north of Lane County. Given the saturated state of the soil across the area, this will maintain an elevated threat for urban, small stream, and river flooding. Landslides in areas of steep terrain will be possible due to saturated soils, as well as debris flows over recently burned areas. The focus once again appears to be northern portions of the forecast area, though the entire region will experience additional rainfall. Snow levels remain high, holding near or above 8000 ft through at least Wednesday, keeping all precipitation as rain in the Cascades as rain, further contributing to elevated runoff and river responses. A gradual downward trend in snow levels is likely late Wednesday night, but too late to influence impacts during the peak of this event. Winds remain a secondary hazard but continue to carry relevance given soil saturation. Overnight gusts generally ranged from 25 to 35 mph across the Advisory area. Similar speeds are expected again later today as the second surge arrives. Even moderate gusts may be capable of uprooting trees due to the extremely saturated ground. Confidence remains moderate to high regarding scattered tree impacts but low regarding exact location. The atmospheric river weakens late Wednesday as moisture transport decreases and the plume begins to dissipate. Showers will persist into Thursday, though rainfall intensity will be much lighter and increasingly confined to higher terrain across southwest Washington and the north Oregon Coast Range. A more stable pattern develops Friday into Saturday as high pressure builds, leading to a notable drying trend. Snow levels gradually lower to around 5500 to 6500 ft through the weekend. Despite the improving weather, hydrologic impacts for slow- responding rivers may linger a bit longer. Soils will remain saturated, particularly across the Coast Range and Cascades, leaving the region sensitive to additional rainfall. ~12 && .HYDROLOGY... A strong atmospheric river remains in place across southwest Washington and northwest Oregon this morning, maintaining an elevated threat of urban, river, and small stream flooding through at least late Wednesday. Significant rainfall has already fallen across much of the region since early Monday, and river responses are now well underway. Additional rainfall today through Wednesday from the second moisture surge will prolong elevated flows, with many rivers already exceeding flood stage, or forecast to exceed flood stage within the next 24-36 hours. Rainfall over the past 24 to 36 hours has already pushed several rivers into flood stage, including record flooding on the Grays River (the old record height was 33.15 ft, which was broken around 10 PM Monday when river levels peaked around 33.4 ft), major flooding on the Naselle River, moderate flooding on the Willapa River, and minor flooding for Nehalem River, Wilson River, Trask River, Beaver Creek, East Fork Lewis River, Miami River, and Washougal River. Elsewhere, many basins continue rising and are expected to respond sharply again as periods of heavy rain continue. While the Siletz River, Cowlitz River (Kelso and Castle Rock), and Johnson Creek are currently not in flood stage or action stage, these rivers are expected to reach minor flood stage late this morning. Expect the Pudding River to reach minor flood stage by late Wednesday. The threat for flooding along small creeks and streams as well as urban flooding, including roadway flooding, will continue through Wednesday. Latest high-resolution guidance favors a band of heavier precipitation lingering over southwestern Washington and far northwestern Oregon this morning, with rates around 0.25 inch per hour or higher. These heavy rainfall rates could make for a hazardous morning commute along the I-5 corridor from Salem north through Portland/Vancouver to Kelso/Longview with abundant water atop area roadways. Ponding of water on roads will increase risk of hydroplaning and car accidents. Periods of heavy rain will also increase the risk for landslides in areas of steep terrain and debris flows over recently burned areas. People, structures, and roads located below steep slopes, in canyons, and near the mouths of canyons may be at serious risk from rapidly moving landslides. A Flood Watch remains in effect across all of southwest Washington and northwest Oregon from now until 4 PM Thursday, except for most of Lane County which has been removed from the Flood Watch. && .AVIATION...A mixed bag of LIFR/IFR/MVFR/VFR cigs and IFR/MVFR/VFR visibilities continues across northwest Oregon and southwest Washington this morning, with cigs and visibilities being lowest from KONP to KSLE and points north where a large band of steady stratiform rain continues. Rain will be heavy at times through Tuesday afternoon, especially during the morning and early afternoon hours north of KEUG. Rain should finally begin to taper off from south to north between 06-12z Wednesday as the aforementioned band of stratiform rain lifts northward over western Washington. Although winds have become less gusty, occasional wind gusts up to 20-25 kt are still being observed inland and up to 30 kt at KONP. Winds will increase along the coast late this morning into the afternoon, especially at KONP where wind gusts will likely approach 35-40 kt. KPDX AND APPROACHES...Expect steady stratiform rain to persist through at least 00z Wednesday, heavy at times this morning before rain attempts becoming relatively light this evening. This will result in persistent MVFR cigs throughout the TAF period, with occasional dips to IFR possible (10-15% chance at any given hour through 20z Tuesday, increasing to a 25-45% chance between 21z Tuesday and 00z Wednesday, and then to 75% by 02z). Although winds have weakened this morning, expect winds to increase again towards 02-06z Wednesday when southerly to southwesterly wind gusts up to 25-30 kt are likely. -23 && .MARINE...Buoy observations from early Tuesday morning showed seas hovering around 13 to 14 ft with weakening winds. Seas should fall to 12-13 ft by Tuesday afternoon and then remain steady through Wednesday night. Seas likely fall to 10 ft or lower by Thursday afternoon. Gale force wind gusts up to 35-40 kt are expected across the inner waters with the passage of a frontal system late Tuesday into Wednesday, with gusts up to 30 kt over the outer waters. That said, gale force wind gusts are likely already occurring across PZZ253. Gusts will likely peak near 35 kt over the Columbia River Bar beginning around sunset Tuesday. Seas and winds will likely fall below small craft advisory criteria on Friday, with relatively quiet conditions expected over the coastal waters over the weekend. -23 && .BEACH HAZARDS...Tidal overflow flooding is possible around high tide Tuesday afternoon, December 9th. Despite total tide forecasts decreasing each day, river levels have risen rapidly due to continued periods of heavy rain. While the Garibaldi tidal gauge is anticipated to only peak near 9 ft around 3-4 PM Tuesday, rivers flowing into the Nehalem and Tillamook Bays are running unusually high. The Toke Point tidal gauge is expected to peak near 9.5 ft around 3-4 PM Tuesday, and near 9 ft at Tongue Point. The Willapa River, Wilson River, Trask River, Nehalem River and Naselle River will likely remain above 80% of flood flow during high tide, and possibly the Nestucca River as well. This will temporarily increase chances for tidal overflow flooding around high tide Tuesday afternoon along the south Washington, north Oregon and central Oregon coast in the low lying areas near bays, sloughs, and lower reaches of the coastal rivers. Therefore, the Coastal Flood Advisory has been expanded to include the south Washington coast, north Oregon coast and central Oregon coast. Additionally, there is an elevated threat for sneaker waves late Wednesday through Thursday along the SW Washington coast south through the central Oregon coast. The swell period increases to around 14-15 seconds with swell heights around 9-11 ft, with swell heights and swell periods decreasing late Thursday night. This will create energetic waves that will present a moderate to high risk for sneaker waves, which are waves that can run significantly farther up a beach than normal, including over rocks and jetties. Sneaker waves can suddenly knock beachgoers off of their feet and quickly pull them into the frigid ocean which may lead to serious injury or drowning. Caution should be used when in or near the water. Always keep an eye on the waves, and be especially watchful of children. -23 && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Coastal Flood Advisory from noon today to 5 PM PST this afternoon for ORZ101-102. WA...Coastal Flood Advisory from noon today to 5 PM PST this afternoon for WAZ201. PZ...Small Craft Advisory until 4 PM PST this afternoon for PZZ210- 251-252. Gale Warning from 4 PM this afternoon to 10 PM PST Wednesday for PZZ210-251-252. Gale Warning until 4 AM PST Wednesday for PZZ253. Small Craft Advisory from 4 AM to 10 PM PST Wednesday for PZZ253. Small Craft Advisory until 10 PM PST Wednesday for PZZ271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

249 FXUS66 KMFR 091123 AFDMFR Area Forecast Discussion National Weather Service Medford OR 323 AM PST Tue Dec 9 2025 .DISCUSSION...Updated Aviation section... && .AVIATION...09/12Z TAFs...A front remains aimed at the Oregon Coast just north of North Bend. This is bringing gusty winds to the coast and a variety of ceiling conditions across the region. Along the coast and just offshore, IFR and LIFR ceilings are expected to prevail through the TAF period, with visibility also lowering this morning as the front slowly sags south. VFR conditions generally prevail across the region, but LIFR conditions are spotted in the Rogue/Illinois/Applegate Valleys, and these lower conditions will prevail through this morning. In the Umpqua Basin, the proximity of the front could limit fog development there, and VFR conditions are currently present, but have added MVFR ceilings when the sun comes. Meanwhile, strong winds aloft will persist near the Cascades and over the east side in Oregon (north of Highway 140) today where higher terrain could experience gusts in excess of 50 mph. This could lead to some low-level wind shear over there (NE of Klamath Falls) since a low-level inversion probably doesn`t allow these winds to mix all the way to the surface in some valleys. Even so, vertical mixing may improve today to allow surface wind gusts to 50 mph from around Summer Lake eastward. && .PREV DISCUSSION... /Issued 235 AM PST Tue Dec 9 2025/ DISCUSSION...Satellite and observations show that low clouds are developing across some west side valleys, including the Rogue Valley. Heavier cloud cover is preventing fog development in more east side spots, including Klamath Falls for now. Radar has a few showers passing in far northern Coos and Douglas counties as they move east tonight. Through the morning, these showers are forecast to reach ~0.25"- 0.50" near the Douglas/Lane County border. Snow levels in the affected areas are above 8,000 feet tonight. The upper level high to our southwest off of central California is still looking to be enough to keep most of the activity north near Portland and Seattle this week. The main areas to see rainfall for the next few days will be the same locations to see it now. Between this morning and Wednesday morning, very northern Coos and Douglas counties, including parts of the Cascades, can expect 0.30"-0.75", with near 1.25"-1.75" near the northernmost part of Douglas County. Most of the rain will fall between this morning and into the evening. Although most of this will be occurring in a 12 hour period, there is a lower concern for flooding with this compared to areas north of us. East side and Northern California have the lowest chances for rain with less than .15" from Chemult to Fort Rock being the most to expect. Although the area will be dry, east side will have to deal with stronger winds between now and this afternoon. A mid-level jet of 50- 60 kt with similar speeds at 300 mb show that strong winds are forecast to reach the surface during this time with gusts near 50 mph. A Wind Advisory is in effect through this evening, and this includes areas near Silver Lake, Summer Lake, and Paisley. Wind gusts near 45 mph have already been reported at Summer Lake early this morning. Please see the NPWMFR for more information. Getting into the middle of the week, the high pressure to our southwest takes control and brings drier conditions through at least the start of next weekend. Earlier models were showing a continued chance of showers at the coast through the work week, but this has started to back off. The EC has also backed off on weekend rain chances, but it is still coming in earlier than the GFS with a Monday morning vs Monday afternoon timeframe. Either way, there is some more agreement that early next week could have active weather in both Southern Oregon and Northern California. In the meantime, we will be watching for how the system the next few days moves through and watch for how the models handle the next week after. -9 MARINE...Updated 200 AM PST Tuesday, December 9, 2025...Gusty south winds and steep wind waves combined with westerly swell will maintain conditions hazardous to small craft through at least today. Winds subside tonight, but west swell persists into Wednesday, especially north of Cape Blanco. Conditions improve for the latter half of the week as swell dominated seas gradually lower. Expecting showers over the waters through mid-week as well which could further reduce visibilities (fog/low clouds expected as well) over the next couple days. && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 10 PM PST this evening for ORZ030-031. CA...None. PACIFIC COASTAL WATERS...Small Craft Advisory until 1 AM PST Wednesday for PZZ356-376. Small Craft Advisory until 10 AM PST Wednesday for PZZ350-370. && $$

162 FXUS66 KEKA 090804 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 1204 AM PST Tue Dec 9 2025 .SYNOPSIS...Areas of dense fog and low chances for coastal drizzle for portions of the North Coast through mid week. Generally dry weather and a warming trend are expected to prevail across NW CA this week, with record warmth likely for the interior. && .DISCUSSION...Pocket of fog and overcast skies are expected along the coast. Fog visibilities are being observed along the North Coast early this morning. Light drizzles to the occasional light shower can be expected to continue along the North Coast, mainly in Del Norte today. Latest guidance only yields trace amounts of measurable rainfall, but persistent light drizzle may lead to a few hundredths accumulating along portions of the North Coast. It will remain dry elsewhere with increasing high temperatures. The persistent ridge of high pressure southwest of the region responsible for blocking Pacific storm systems will strengthen and nose eastward through the workweek. Significant warming will occur as a result. The current forecast yields interior high temperatures reaching 10-20F above climatological norms midweek through the weekend. NBM shows a high probability (70 to 80%) for the warmer interior valleys to exceed 70 F Thursday and especially Friday (80 to 90%). When looking at NBM probabilities for exceeding 75F, the Ukiah area shows probabilities of 50% for Thursday and Friday. This would likely break the high temperature record of 72F from 1958 for Ukiah on Friday if the forecast holds. Ensembles and clusters are hinting at the weaken of the stubborn ridge through the weekend. Precipitation chances start to increase through the latter portion of the weekend. However, any meaningful breakdown of the ridge or zonal flow may not occur into early next week, leading to a further increase of rain chances. JJW/DS && .AVIATION...(06Z TAFs)...The set up for fog could bring or prolong LIFR conditions through the TAF period and well into Tuesday morning for the coastal terminals. KCEC has been under a persistent LIFR regime since 21z. KACV has faired a bit better with inconsistent improved periods of MVFR yet dominated by IFR mostly. Subsidence is compacting and stratifying layers of clouds near the ground and up to 1000ft with most ceilings at KCEC around 300ft. Conditions are expected to lift a bit as fronts approach Tuesday and possibly overnight into Tuesday morning. Light drizzle could be a hindrance to visibility along with the fog with calm winds. && .MARINE...Generally light winds are forecast through Tuesday morning, with south winds forecast north of Cape Mendocino and west- northwest winds forecast south of the Cape. Another mid-period northwest swell will fill in this afternoon and evening, peaking at 7-9 ft at 13 seconds overnight into Tuesday. Combined seas may briefly exceed 10 ft in some areas. Northerly winds are also likely to trend northward Tuesday and Wednesday. Northerly wind gusts of 15- 25 kts are possible south of Cape Mendocino Tuesday and Wednesday afternoons and steep wind waves of 5-7 ft are possible. Additional mid-period northwest swells will continue to fill in through the week, keeping seas elevated. JB && .BEACH HAZARDS...An increased threat of sneaker waves is expected for the Del Norte, Humboldt, and Mendocino coastlines this Thursday. A mid-period westerly swell generated by a storm currently located near 45N,160W will enter the coastal waters early Thursday morning. A lack of local wind waves will allow this swell to dominate the sea state over an existing swell, creating beach conditions that could look deceivingly calm. Forecast confidence continues to grow as the swell passes NOAA/NDBC buoys Wednesday morning. Remember to never turn your back to the ocean, and to avoid steep beaches, jetties, outcroppings, and rocks during these events. DS && .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

873 FXUS66 KMTR 091154 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 354 AM PST Tue Dec 9 2025 ...New AVIATION, MARINE... .KEY MESSAGES... Updated at 132 AM PST Tue Dec 9 2025 - Tule fog and stratus will clear this afternoon - Quiet weather with warmer temperatures through Friday - Light rain possible next week && .SHORT TERM... Issued at 132 AM PST Tue Dec 9 2025 (Today and tonight) Another round of morning clouds and patchy fog across the Bay Area. The coverage is less than yesterday and these clouds will clear in the afternoon as temperature climbs a few degrees warmer than recent days. The prolonged ridging pattern continues with the amplitude notching up over the next few days. The Eastern Pacific high now extends a ridge across northern California, and there is even a somewhat uncommon cut off high way up at 250 mb directly over the Bay Area. This is the jet stream altitude where the average wind speed this time of year is around 60 knots. We`ll be lucky to break 10 knots on the 12Z sounding. This vertically stacked dome of high pressure is leading to widespread subsidence, calm winds, stagnant surface air, and warmer than normal temperatures. && .LONG TERM... Issued at 132 AM PST Tue Dec 9 2025 (Wednesday through Monday) While the ridge has been the main scapegoat for the ongoing Tule Fog, the increasing ridge intensity will compress this cool moist layer closer to the surface and limit it`s horizontal spread to the Central Valley and colder interior valleys across the Bay Area. Air quality may also suffer as a result. The 850 mb temperature will climb to around 17C by Wednesday, and park there until Friday. That`s around 10C warmer than normal, close to the average for June. Surface temperatures will respond and warm up to 10F above normal, pushing some clear areas of the Bay Area and Central Coast to the mid 70s. This heat will peak on Thursday with noticeable cooling by the weekend. Despite the warm afternoons, the dry atmosphere (PW 0.3- 0.5") and long December nights will still bring morning temperatures into the 40s. The ridge axis will finally move through this weekend, allowing the pattern to become more zonal. This opens the door for some rain next week. While zonal flow doesn`t support strong storms or atmospheric rivers, it looks likely that we`ll at least end the dry streak sometime next week, possibly as early as Monday. && .AVIATION... (12Z TAFS) Issued at 349 AM PST Tue Dec 9 2025 Higher confidence in clearing out of the fog and stratus today for North Bay terminals. Day-to-day change gradually improving as high pressure builds aloft. Patchy stratus invof SF Bay providing lower confidence there, but based on persistence forecast KOAK likely to remain VFR. Vicinity of SFO...Patch of stratus and fog moving along the peninsula likely to persist through sunrise, clearing to VFR in the few hours following. Lower chance of stratus overnight into Wednesday morning compared to this morning. Medium confidence in cigs holding off until just before sunrise Wednesday. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...High confidence in VFR through the TAF period. Light drainage offshore winds overnight with light onshore flow during the afternoons. && .MARINE... (Today through Sunday) Issued at 349 AM PST Tue Dec 9 2025 Northwest winds increase to a strong breeze today into mid week across the outer waters. Gentle breeze persists across the inner coastal waters. A new, long period northwesterly swell is expected by midday Wednesday, lasting into the early weekend. && .BEACHES... Issued at 132 AM PST Tue Dec 9 2025 Long period swell will impact the coast Wednesday - Friday. This energy brings strong rip currents, an increased risk for sneaker waves, and large breaking waves. NW swell around 8 feet with a 15 second period will translate to breaking waves up to 15-20 feet. These conditions may warrant a Beach Hazards Statement, particularly with the warm weather likely luring more people to the Beach. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement from Wednesday morning through Friday evening for CAZ006-505-509-529-530. PZ...Small Craft Advisory until 9 PM PST this evening for Pt Pinos to Pt Piedras Blancas 0-10 nm. && $$ SHORT TERM...Flynn LONG TERM....Flynn 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

258 FXUS66 KOTX 091221 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 421 AM PST Tue Dec 9 2025 .KEY MESSAGES... - Decreasing winds Tuesday morning. - Heavy mountain rain will bring a risk for flooding in the Cascades and the Idaho Panhandle, especially in steep areas and near burn scars. && .SYNOPSIS... An active weather pattern will impact the area through the week. A series of warm and wet weather systems will result in periods of heavy mountain rain, lowland rain, high mountain snow, and gusty winds. && .DISCUSSION... ...STRONG ATMOSPHERIC RIVER RIVER EVENT RETURNS TONIGHT THROUGH THURSDAY BRINGING POTENTIAL FOR FLOODING, AS WELL AS ROCK AND MUD SLIDES IN THE CASCADES AND IDAHO PANHANDLE... Today: The Atmospheric River responsible for the steady rains and windy conditions over the past 24 hours will slide south into Oregon today, before lifting back north over the region. This will allow conditions to dry out, along with a rapid decrease in winds between the early to late morning hours as pressure gradients relax. Significant rains over the past 24 hours along with snow melt in the Cascades and ID Panhandle will lead to continue rises on area rivers, while small streams are likely to fall with the break in the rain. Tuesday Night through Thursday: The next atmospheric river lifts north as precipitable water values increase to 250-300% of normal. An initial warm front will help produce widespread precipitation initially for Tuesday Night. But after the front passes, rain is expected to become mainly focused again over the Cascades and ID Panhandle for Wednesday and Thursday as strong downslope for off the Cascades dominates across most of Central and Eastern Washington. Snow levels at the onset will range from 3500-4500 feet allowing for mountain snow to initially fall Tuesday evening with 2-4 inches of wet snow over the mountain passes including Stevens, Loup Loup, and Sherman. Lighter amounts up to 2 inches are possible for Lookout Pass. Snow levels rapidly rise to 7000-9000 feet by Wednesday morning. The atmospheric river remains nearly stationary Wednesday into Thursday, aimed at the Central and Northern Cascades into the ID Panhandle producing heavy rain. The ECMWF, GFS, and Canadian Ensembles are producing another 3-6 inches of rain in Western Chelan county, with up to 6-10 inches along the Cascade crest. For the ID Panhandle 1-4 inches is forecast. This combined with snow melt will lead to sharp rises on rivers and streams. In the Cascades river rises will be monitored closely for the Stehekin, Wenatchee, and Entiat Rivers as well as the small streams. For the ID Panhandle the St Joe and Coeur d`Alene Rivers are the main concern as well as small streams. Another concern for the Cascades will be rock/mud slides, especially so in steep terrain and near newer burn scars including the Pioneer above Stehekin, Sugarloaf, and Labor Mountain burn scars. A flood watch remains in effect through Thursday afternoon for Chelan, Benewah, Kootenai, and Shoshone counties. Another story will be the abnormally warm temperatures. The next atmospheric river brings an increase in southwest winds, with very mild 850mb temperatures of 5-9C. This may allow high temperatures to reach the mid 50s to mid 60s over much of the Columbia Basin, and down into the LC Valley, which would be near records for Wednesday. And Wednesday Night lows will only drop into the upper 30s and 40s, except mid 50s for the LC Valley. These temperatures are as much as 20 to 25 degrees above normal. Thursday Night through Monday: The atmospheric river lifts norths and weakens heading into Friday but enough moisture and upslope flow lingers in the Cascades and ID Panhandle for more precipitation but with decreasing intensity. Snow levels also come down a bit, but still high around 4000-6000 feet. On Sunday into Monday ensembles show another round of precipitation moving in as moist precipitable water plume around 175-200% of normal takes aim at the area from southwest to northeast. This is likely to be another mild system with rain and high mountain snow, but amounts looks much less compared to those this week. JW && .AVIATION... 12Z TAFs: Winds will decline through the morning. An atmospheric river is bringing showers to the KPUW through 14z before shifting south. There has been enough downslope flow off the Cascades to dry out the boundary layer, with VFR conditions favored for the majority of Central and Eastern Washington through the day on Tuesday. But then another round of rain moves in Tuesday evening as the atmospheric river lifts north again, with widespread CIGS of MVFR expected to develop, locally to IFR. .FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate to High confidence on VFR conditons through Tuesday. Moderate confidence on the IFR-MVFR reforming overnight. Low confidence on the timing of occurring. JDC ----------------------- 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 49 39 53 47 52 42 / 10 100 60 70 60 30 Coeur d`Alene 48 38 53 47 51 42 / 20 100 90 90 80 50 Pullman 50 40 55 49 52 46 / 70 100 70 60 80 50 Lewiston 56 46 62 54 60 50 / 70 100 40 50 60 40 Colville 48 32 47 37 47 32 / 10 100 50 70 60 30 Sandpoint 47 34 48 44 48 37 / 30 100 90 90 90 50 Kellogg 49 37 51 47 49 44 / 80 100 100 90 90 70 Moses Lake 52 40 58 47 56 40 / 30 90 20 40 40 10 Wenatchee 49 39 55 45 52 43 / 30 100 60 70 60 20 Omak 47 36 47 38 47 35 / 10 100 40 60 50 20 && .OTX WATCHES/WARNINGS/ADVISORIES... WA...Flood Watch through Thursday afternoon for Central Chelan County-Wenatchee Area-Western Chelan County. Wind Advisory until 7 AM PST this morning for Lower Garfield and Asotin Counties-Northeast Mountains-Spokane Area- Upper Columbia Basin-Washington Palouse. ID...Flood Watch through Thursday afternoon for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-Northern Panhandle. Wind Advisory until 7 AM PST this morning for Central Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse- Lewiston Area-Northern Panhandle. && $$

100 FXUS66 KPDT 091207 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 407 AM PST Tue Dec 9 2025 .UPDATED AVIATION...12 TAFs...While an ongoing rain shadow keeps rain pinned along the mountains, VFR conditions will prevail during overnight hours for all sites with light rain currently over KDLS. Through most of the day Tuesday, rain is forecast to develop for all sites. KDLS, KPDT, and KRDM may reach to MVFR conditions or lower as VSBYs and/or CIGs drop from the low clouds and potential mist Tuesday morning into early evening hours. KPSC may see MVFR conditions around early Tuesday evening as light rain arrives starting late Tuesday afternoon(<30% confidence). Southwest to west gusty winds are expected to be at 20-30kts or higher for most sites overnight into Tuesday morning. However, winds gusts up to 30kts could return for KBDN late Tuesday morning and for KRDM early Tuesday evening. Feaster/97 && .PREV DISCUSSION... /issued 329 AM PST Tue Dec 9 2025/ .DISCUSSION... Key Points: 1. Significant rainfall leading to flooding in some areas through the week. *Flood Advisory and Warnings Active* 2. Breezy conditions through Thursday 3. Warm temperatures will continue through the long term Current radar shows much of the incoming rainfall to be mostly on the west side of the Cascades with some spill over in portions of Kittitas and Yakima Counties as well as over the higher peaks of the Blues. Winds are expected to begin settling through the morning with ground observation showing gusts to be between 25-35 mph still. Winds are expected to settle after 3-5 AM as the passage of the front continues to move east. Today through Thursday afternoon...Models show a relatively strong atmospheric river has set up along the coast of WA and OR and persisting through Thursday. This will bring widespread significant rainfall to the region with QPF totals for today through Thursday afternoon totaling to nearly 3 inches along the eastern slopes with higher amounts along the crests. Models also show nearly 1-1.5 inches of precipitable water which is substantially higher than the normal. CAMs raw ensembles (HREF) show the crests to the eastern slopes through Ellensburg and the Dalles as well as the eastern mountains through the Grande Ronde Valley and into Wallowa Valley will see 0.05-1 inch or more of precipitation today (Tuesday)with 80- 90% confidence. This will continue through the day with ensembles showing up to another inch of precipitation in the aforementioned areas again Wednesday. However, backing off along the eastern mountains and the Grande Ronde Valley where only 0.25-0.5 inches are expected (60-80%). NBM raw ensembles show 25-65% chance of the lower elevations such as the Basin and foothills of the Blues will see 0.25-0.30 inches in a 48 hour period and central OR will see 0.10 inches. With the significant rainfall across the WA Cascades, many rivers are expected to reach/exceed bankfull through tomorrow. Naches at Naches, Yakima at Horlick and Easton are all exceeding action stage and into minor so a Flood Warning has been issued for those locations. All other rivers in the area are still at or nearing action stage and are continuing to be monitored as the event continues to unfold. Models show another cold front to make its way across the region beginning Tuesday night and persisting through Wednesday bringing another round of breezy conditions. Pressure gradients along the Cascades with this front are not as strong as the previous with only 7-9 mb gradient. Winds will be from the southwest between 15-25 mph sustained with gusts to 40 mph and will affect the wind prone Gap areas as well as the eastern slopes, Horse Heaven Hills and the Northern Blues of WA. After Wednesday, models show a more zonal flow will rest over the region bringing winds back to a more diurnal flow. Lastly, models show that not only did this AR tap into an abundance of moisture, but also in a abu-tropical flow that will bring with it increasing temperatures. With the influx of warm air, temperatures are expected to be 10-15 degrees warmer than seasonal average today increasing to 15-25 degrees above seasonal average Wednesday. Short term raw ensembles show elevations below 3500 feet will see temperatures in the low to mid 50s Tuesday, with the exception of Kittitas Valley where temperatures will be in the mid to upper 40s (70-90% confidence). Moving to Wednesday, raw ensembles show the same areas beginning to see temperatures in the low to mid 60s with Kittitas Valley now seeing low to mid 50s (60-80% confidence). Temperatures will steadily decrease as we move into the later portion of the week, however, temperatures are expected to stay 10- 20 degrees above climatological normal. Essentially saying temperatures will remain in the low to mid 50s. 90 && .PRELIMINARY POINT TEMPS/POPS... PDT 56 45 65 51 / 100 90 40 20 ALW 54 46 64 54 / 90 90 60 30 PSC 56 44 66 53 / 80 90 20 20 YKM 50 39 60 48 / 80 100 60 50 HRI 57 46 66 52 / 90 90 20 20 ELN 46 35 56 44 / 70 100 70 70 RDM 57 44 63 37 / 70 50 10 0 LGD 51 41 58 45 / 100 100 50 20 GCD 51 45 58 40 / 90 70 10 10 DLS 56 48 63 55 / 100 100 70 60 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Wind Advisory until 7 AM PST this morning for ORZ041-044-507-508- 510. WA...Wind Advisory until 7 AM PST this morning for WAZ024-027>029-521. Flood Watch through Friday morning for WAZ026-027-521>523. && $$ SHORT TERM...90 LONG TERM....90 AVIATION...97

511 FXUS65 KREV 090903 AFDREV Area Forecast Discussion National Weather Service Reno NV 103 AM PST Tue Dec 9 2025 .KEY MESSAGES... * Dry weather and near record warmth expected this week. * Hazy skies and minor reductions in air quality possible each morning across lower urban valleys. * Next week may bring periods of increased winds and precipitation chances, but confidence remains low. && .DISCUSSION... A strong upper level ridge off the CA coast and extending across much of CA-NV will keep dry conditions going through at least this weekend, with the main storm track remaining over the Pacific Northwest. Unseasonable warmth will prevail with 850-700 mb layer temperatures rising by about 3-4 degrees C compared to yesterday. While light winds will limit mixing, this low level warmup will allow highs to climb above 60 degrees across most lower elevations west of US-95 and also into many Sierra communities today through Thursday. Record highs at Reno and South Lake Tahoe airports are well within reach, especially today (65 and 58 degrees, respectively) and Thursday (64 and 59 degrees), while Wednesday`s current records of 67 at KRNO and 63 at KTVL will be a bit more of a challenge to reach. A slight westward shift of the ridge axis from Friday-Sunday will bring a slight cooling, but highs will remain 10-15 degrees above average. While we`re in this strong ridging pattern, cloud cover will be limited to occasional passing swaths of cirrus mainly north of I-80. Due to low-level inversions, expect valley haze (and patchy fog for valleys around Truckee) each morning this week before dispersing by the early afternoon hours. For next week, medium range guidance has been hinting at a potential change to a more active weather pattern with periods of increasing winds and valley rain/mountain snow. However, the majority of the ensemble data is now trending toward a longer delay before this change occurs. A weakening trough passage could still make a small dent in the prevailing ridge next Monday or Tuesday, but the most likely result is low-end (15-30%) light shower chances from the Sierra crest northward to the OR border and an uptick in SW winds mainly for higher elevations. Then after this system exits, signals are pointing toward a rebuilding ridge through at least the middle of next week. Given daily fluctuations with wetter/drier trends as each ensemble guidance run arrives, the confidence in the evolution of next week`s overall weather pattern remains on the low side. MJD && .AVIATION... Minimal weather concerns for aviation this week as high pressure maintains VFR conditions and light breezes. Conditions remain favorable (50-70% chance) for patchy FZFG formation at KTRK during the next few mornings, mainly between 10-16Z. Haze from valley inversions could produce minor reductions in slantwise visibility each morning this week, primarily for W NV sites. MJD && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

986 FXUS66 KSTO 082153 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 153 PM PST Mon Dec 8 2025 .KEY MESSAGES... - Periods of low clouds, mist, fog and unseasonably cool temperatures continue in the Central Valley, Delta and lower foothills this week, with some warming by late week - Increasingly mild temperatures with sunny skies and dry weather are expected over higher terrain this week && .DISCUSSION... ...Today - Sunday... Eastern Pacific high pressure ridging continues a stagnant pattern across the region, with a strong inversion keeping fog and low stratus over the Valley and Delta and into the lower foothills. Patchy fog has primarily been observed over the northern Sacramento Valley and in the foothills (1500-2000 feet). Fog in the Valley has diminished this afternoon, but lingers in the foothills where the low clouds intersect the terrain. This pattern is expected to continue with low clouds persisting and some patchy fog reforming in the Valley again tonight. Winds remain generally light and variable. This pattern is expected to persist through the week and even into the weekend as the high pressure ridge continues to build. Dry weather continues across the region. The exception to this is periods of mist and sprinkles at times with the low clouds and fog, which may wet the ground. The low clouds continue to keep temperatures unseasonably cool in the Valley and Delta, while higher terrain experiences sunny skies and above normal temperatures. The building high will bring warming temperatures to the area, especially over higher terrain. Stratus and fog will limit this warming for portions of the the Valley and Delta that remain covered, though, so there may be little change in those areas this week. The northern Sacramento Valley has the best potential for seeing some clearing and increasing temperatures. ...Next Week... A pattern change is projected for early next week, but there remains quite a bit of uncertainty in the timing and intensity of this system. Current forecast shows the potential for precipitation north of I-80, especially for the mountains. The best chances expected over the mountains of Shasta County, but little to no impacts are expected at this point. Stay tuned for forecast updates. && .AVIATION... Lingering low cigs and mist across the Central Valley continue into this evening with IFR/LIFR conditions, although some sites may very briefly see MVFR/VFR visibility around 22-24Z, mainly for TAF sites north of Sacramento. Another round of BF/FG and low stratus returns after 03Z with areas of IFR/LIFR ceilings once again expected to persist through the day. Light and variable surface winds less than 12kts. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

689 FXUS65 KMSO 091023 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 323 AM MST Tue Dec 9 2025 .DISCUSSION... KEY MESSAGES: - Significant Atmospheric River, potentially historic, to bring heavy rain, leading to hydrological concerns and flood risk. - Gusty winds this morning across northwest Montana, with risk for power outages from downed trees. - Brief burst of accumulating snow late tonight into Wednesday morning for northwest Montana valleys near the Continental Divide - Heavy, wet snow across backcountry and high elevations areas above 5000-8000 feet this week. The first plume of anomalous moisture from an ongoing atmospheric river event is currently peaking over western Montana and north central Idaho. Rainfall rates of 1.50 to 2.00 inches in 6 hours have been noted in the higher terrain of north central Idaho overnight, with notable rises in small streams and creeks. This first moisture plume will sag southwards through the morning as a cold front passes through the region. While this introduces a brief lull in the heaviest precipitation intensities for northwest Montana, widespread precipitation will continue further south, especially through Idaho County. Gusty southwest to west winds will develop this morning as the cold front passes, with widespread gusts to 40 mph still anticipated, mainly for valleys of western Montana, with higher speeds in exposed terrain. Snow levels will briefly lower across the region to roughly 3000 feet in northwest Montana and 5000 feet in north central Idaho. The next surge of anomalous moisture will arrive into the region late tonight and continue into Thursday. This second surge looks similarly strong to the ongoing wave, however it appears to be more prolonged, peaking for a 24 hr period (or possibly longer). Before warm air scours out the cold air Wednesday afternoon, snow levels will dip low enough (3000-4000 feet) to produce winter impacts late tonight into Wednesday morning. High-resolution guidance indicates a quick burst of moderate to heavy snow is possible for northwest Montana, including Seeley Lake and Marias Pass. Snowfall rates of 0.5" to 1" per hour may create slick conditions and reduced visibility for the Wednesday morning commute. Even the Flathead Valley could see a brief transition to wet snow. Looking ahead, confidence is increasing that anomalous moisture will persist through the remainder of the week (Thursday- Saturday). A complicating factor is an arctic airmass that is forecast to bank up along the Northern Continental Divide. While strong westerly winds aloft will likely keep the arctic front from crossing the divide, this setup introduces a classic overrunning scenario, potentially creating winter conditions (snow and ice) that extend into the valleys of northwest Montana by Thursday morning. The interaction between this dense, shallow cold air and the overriding subtropical moisture will be a critical focal point for the extended forecast. && .AVIATION...Widespread mountain obscuration will persist through the forecast period as deep moisture continues to stream into the Northern Rockies. While the heaviest precipitation from the initial atmospheric river plume is shifting south into Idaho County this morning, widespread low ceilings (MVFR) remain across the terminals. A cold front sweeping through this morning will turn surface winds to the west-southwest. Expect widespread gusts of 25 to 35 kts at valley terminals (KMSO/KGPI), with gusts exceeding 40-50 kts over exposed terrain. This interaction with the terrain will generate moderate to severe mechanical turbulence and areas of Low Level Wind Shear (LLWS). A brief lull in precip intensity is possible this afternoon, but ceilings will struggle to lift significantly. Conditions deteriorate rapidly again late tonight (after 06Z Wednesday) as the second moisture surge arrives. Snow levels will briefly crash to between 3000-4000 feet late tonight. This will introduce a period of IFR conditions due to heavy, wet snow, particularly for KGPI and locations along the Northern Continental Divide. Snowfall rates of 1 inch/hour are possible in these bands before warm air scours out the cold air Wednesday afternoon. && .HYDROLOGY...Recent rainfall has already primed regional soils and triggered rises on waterways, and the incoming second surge will further exacerbate these conditions. This next wave is forecast to deliver an additional 2 to 5 inches of liquid precipitation to the terrain of north-central Idaho and northwest/west-central Montana, with valleys receiving between 0.50 and 2.00 inches. Consequently, cumulative storm totals by Thursday morning are projected to reach localized amounts of 5 to 9 inches of liquid. To place this in context: if these forecast 72-hour totals verify, this would represent a historic rainfall event with an Average Recurrence Interval (ARI) of 50 to 100 years (a 1% to 2% chance of occurring in any given year). The primary concern, however, extends beyond pure rainfall intensity. This system is driven by a warm, subtropical airmass that will drive freezing levels well above 6,000 to 8,000 feet by Wednesday. This will induce a significant rain-on-snow event, rapidly ripening and melting the existing low-to-mid elevation snowpack. The combination of heavy, prolonged rainfall and snowmelt contribution is expected to overwhelm small creeks and streams first, followed by significant rises on mainstem rivers. Given this setup, numerous Flood Watches remain in effect. Residents in steep terrain should also remain alert for rock and mudslides, particularly in north-central Idaho and northwest Montana where the ground is deeply saturated. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...Flood Watch through Thursday afternoon for Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower Clark Fork Region...Potomac/Seeley Lake Region...West Glacier Region. Wind Advisory until 8 AM MST this morning for Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower Clark Fork Region. Wind Advisory until 11 AM MST this morning for West Glacier Region. Winter Weather Advisory from midnight tonight to 11 AM MST Wednesday for Potomac/Seeley Lake Region...West Glacier Region. ID...Flood Watch through Thursday afternoon for Lower Hells Canyon/Salmon River Region...Northern Clearwater Mountains...Orofino/Grangeville Region...Southern Clearwater Mountains. && $$

750 FXUS65 KBOI 090954 AFDBOI Area Forecast Discussion National Weather Service Boise ID 254 AM MST Tue Dec 9 2025 .SHORT TERM...Today through Thursday night...Warm, moist air mass, with an atmospheric river extending across the eastern Pacific along 45N then E-SE-ward through our CWA, will continue through Wednesday. The atmospheric river will produce moderate to locally heavy rain in the northern third of our CWA, i.e., Baker County/OR, and Idaho north of the Snake Basin, with snow level staying above 8000 feet MSL. Northern rivers will run higher but should stay safely below flood stage, with most cresting Friday. The atmospheric river and steady rain will shift slowly north Wednesday and Thursday allowing our CWA to dry out. High temps today will be several degrees warmer than yesterday as yet another warm front passes through, and Wednesday looks warmer still, reaching 60 degrees in many southern valleys. Only slight (1-3 degree) cooling Thursday. On the other hand, partial clearing will allow colder nighttime lows and patchy fog in wind-sheltered southern valleys. Winds through Thursday will be light to moderate southeast through southwest, strongest in south- central Idaho this afternoon with gusts 30 to 35 mph. .LONG TERM...Friday through Tuesday...Come Friday, a building ridge will have pushed the jet stream and Pacific moisture plume north of our area. With high pressure setting in beneath the ridge, we will be looking at dry conditions with partly cloudy skies through Sunday. While the ridge will keep our area dry, it will introduce its own subset of hazards. Model soundings show valley inversions developing under the subsidence aloft, This is also marked by mixing heights below 2000 ft AGL. With the added surface moisture, thanks to the AR event in the short-term, fog and low stratus will likely be in play Friday- Sunday. Another consequence of the inverted conditions is increased uncertainty with regard to temperatures. While a warmer airmass will be in place, colder air could get trapped in the valleys. For now, am maintaining temperatures 10-15 degrees above normal (at the higher end of that range on Friday, gradually decreasing toward the lower end by Sunday). The added caveat would be in the inversion influence, by both the cooler air trapping and fog/low stratus. This could tamper down temps below the inversion... and un-luckily for us, are not captured well by the guidance, especially this far out. Beyond Sunday, unsettled conditions will make their way back into the forecast. A shortwave and its associated cold front is set to flatten down the ridge early this coming week. However, the timing of the first system is still tricky to pin down. While the GFS and Euro ensemble suites agree on a system early next week, they diverge on the timing. The Euro suite brings the system in earlier Monday, whereas the GFS suite is lagging a little behind and holding off until late Monday/early Tuesday. In either case, this supports increasing precipitation chances come Monday, increasing further through Tuesday. && .AVIATION...Precip continuing across far E-Oregon and much of SW-Idaho. VFR conditions in light precip and MVFR/LIFR ceilings in heavier rain and high-elevation snow. LLWS through the morning. Snow Levels: 6.5-7.5 kft MSL north of the Snake Plain, 8-9.5 kft MSL in/south of the Snake Plain. Surface winds: SW-SE 5-15 kt SW with gusts to 20-35 kt outside of the Treasure Valley. Winds aloft at 10kft MSL: W-NW 40-55 kt. KBOI...Generally VFR with light rain continuing through this evening, periods of MVFR ceilings this afternoon. Threat of LLWS through the morning. Surface winds: SE 8-12 kt this morning, becoming northerly up to 10 kt this afternoon. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...None. OR...None. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.x.com/NWSBoise SHORT TERM...LC LONG TERM....NF AVIATION.....NF

421 FXUS65 KLKN 090839 AFDLKN Area Forecast Discussion National Weather Service Elko NV 1239 AM PST Tue Dec 9 2025 .KEY MESSAGES... Updated at 1217 AM PST Tue Dec 9 2025 * Quiet conditions and seasonally warm temperatures continue thru the week under high pressure. * Potential for precipitaton returns early next week. && .UPDATE... Issued at 1217 AM PST Tue Dec 9 2025 The current forecast is on track and no significant updates are required. && .DISCUSSION... (This evening through next Monday) WEATHER PATTERN OVERVIEW: The quiet weather pattern continues today as a ridge of high pressure remains stationed offshore of the southwestern United States. Northwest flow over the ridge axis will bring periods of mid and high level clouds thru the short term, particularly across northern Nevada, but no precipitation is expected. Latest numerical model output continues to depict dry weather thru the week as any chances for precipitation have been curtailed by the latest model runs. Highs each afternoon will warm to well above normal levels with the warmest readings occurring during the middle to latter portions of this week. Highs will generally range in the low 50s to low 60s with overnight lows mostly in the 20s to low 30s. Record to near record warmth is forecast across the region. Breezy afternoon winds are expected today and Wednesday across the northern portions of Elko and Humboldt counties with wind gusts to 25 mph. Potential for precipitation returns early next week though confidence is low due to substantial disagreement between various numerical models. FORECAST CONFIDENCE & DEVIATIONS: Confidence in the forecast continues to be high in the short term as an upper level ridge remains the dominant weather feature. Decreased confidence early next week as indicated previously. && .AVIATION... VFR conditions will persist through the next 24 hours along with light winds. && .LKN Watches/Warnings/Advisories... None. && $$ DISCUSSION...92 AVIATION...92