791 FXUS66 KSEW 081702 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 902 AM PST Sun Dec 8 2024 .SYNOPSIS...A low pressure system will continue to produce areas of precipitation through Sunday afternoon, including snow in the mountains, and rain in the lowlands. A couple of dry days will follow on Monday and Tuesday as high pressure builds back in. The pattern will return to unsettled on Wednesday through next weekend with several systems passing through bringing additional chances of precipitation. && .SHORT TERM /TODAY THROUGH TUESDAY/...The latest forecast remains on track with no updates this morning. Precipitation continues across western Washington this morning from a surface trough just off the coast. A previous cold frontal boundary yesterday has brought snow levels down to around 3,000 feet as of yesterday. This has transitioned the precipitation to snow in the mountains, with a lot more still to fall in the Cascades and Olympics today. The heaviest of this will be concentrated in the Cascades, where showers will likely linger longer post front through the evening (via convergence zone). Still expecting another half inch to an inch and a half of liquid through the day today in this region (equivalent to an additional 6 to 12 inches at Snoqualmie/Stevens/White Passes). Some of the highest peaks may see as much as 2 feet of snow. Will continue the winter headlines in place, and again the heaviest of the snow will fall through around noon before tapering down this afternoon. Rates may reach 1-2 inches an hour (especially in convergence/convective areas). For lowland areas, the activity will continue to produce rain showers throughout the day. Coverage is not expected to be as widespread today. This will limit QPF to around a tenth to a quarter of an inch for most areas (half an inch along the coast). Additionally, for beaches along the Pacific Coast, waves are expected to remain below 20 ft (closer to 16 ft) - below the threshold needed for a high surf advisory. The breezy south winds in the Cascades will diminish going into the afternoon as well, and they will be light out of the south everywhere else. Moving ahead, the trough/low will move inland today and again fill over the Northern Plains. A ridge will follow the trough - expect high pressure to begin building back in Monday and Tuesday. Cloud cover (with some patchy fog) will slowly decrease Monday with some sunshine by the afternoon. The polar jet will bring some cooler Canadian air in, which will knock high and low temperatures down into the mid 40s/low 30s respectively. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Majority of the models are now showing a shortwave trough following the ridge Wednesday into Thursday with an associated frontal system. This will increase precipitation chances Wednesday into Thursday (but it does not appear the precipitation will be heavy at this time). A more prominent trough appears to develop next weekend, but there`s no good agreement at this time on where it will go inland, or how strong it will be. Temperatures will remain relatively steady with lows in the mid 30s, and highs in the 40s. HPR && .AVIATION...An upper level trough will move through the area midday. Northwesterly flow aloft will become northerly behind the trough. Surface high pressure building offshore will move inland tonight and Monday. Mostly MVFR ceilings expected into the afternoon hours. Ceilings will improve to VFR mid afternoon. Ceilings will then lower back down to MVFR with pockets of IFR 06z-09z tonight. MVFR ceilings with isolated IFR ceilings are expected to persist through most of Monday morning. KSEA...MVFR ceilings improve to VFR mid afternoon. Ceilings are expected to lower to MVFR around 06z tonight and continue through Monday morning. Surface winds southerly 8 to 12 knots will ease to 4 to 8 knots after 21z. Winds become variable 5 knots or less after 06z tonight. Felton/27 && .MARINE...Surface high pressure will rebuild across the waters today and move inland tonight. The ridge will remain over the waters into Wednesday. Another front will reach the area late Wednesday into Thursday. Small craft advisory winds over portions of the coastal waters as well as the Central and Eastern Strait of Juan de Fuca will ease below 20 knots late morning/early afternoon today. Winds remaining below 20 knots through Wednesday. Possible small craft advisory winds coastal waters with the next front late Wednesday or Thursday. Seas 10 to 15 feet subsiding Monday morning to less than 10 feet. Seas building back over 10 feet, 10 to 12 feet, Wednesday night and Thursday. Felton && .HYDROLOGY...Shower activity today will not be hydrologically significant with snow levels lowering. The flood watch for the Skokomish river in mason county will be cancelled with this forecast package. Next round of precipitation later in the week at this point looks like it will only cause minor rises on area rivers. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Winter Storm Warning until 4 PM PST this afternoon for West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes. PZ...Small Craft Advisory until 6 AM PST Monday 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-Grays Harbor Bar. Small Craft Advisory until 6 PM PST this evening for West Entrance U.S. Waters Strait Of Juan De Fuca. && $$

626 FXUS66 KPQR 081713 AFDPQR Area Forecast Discussion...UPDATED National Weather Service Portland OR 912 AM PST Sun Dec 8 2024 Updated Aviation Discussion .SYNOPSIS...An upper level shortwave on the backside of yesterday`s trough will push through the area today, bringing a renewed round of scattered rain showers, except snow showers for elevations above 3000 ft. High pressure and low-level offshore flow returns Sunday night and lingers through at least Tuesday night, bringing a return to dry weather with widespread valley fog and low stratus. Unlike our last stretch of dry weather, high pressure will break down quickly with increasing chances for rain late Wednesday into Thursday. && .SHORT TERM...Sunday through Tuesday night...Post-frontal rain showers will continue on Sunday, except snow showers for elevations above 3000 feet. Patchy morning fog is also being observed, but the coverage of fog is not widespread enough to warrant any dense fog advisories. Locations that are experiencing fog will likely see fog lift by mid morning. Hi-res model guidance suggests showers will increase in coverage this afternoon in response to an upper level shortwave and associated vort max trailing behind yesterday`s trough passage. Although there will be minimal impacts in the lowlands, there will be some impacts in the Cascades. Expect winter driving conditions on US26 near Government Camp and on US20 at Santiam Pass today with several more inches of snow falling before showers diminish across the area Sunday night. Showers will be diminishing in response to the return of high pressure, which will bring another stretch of dry weather Sunday night through at least Tuesday night. With a strong surface temperature inversion developing and minimal low-level mixing, expect widespread valley fog and low clouds to develop Sunday night and then linger through most of the day Monday. The HREF backs this up well, showing a 50-75% chance for widespread dense fog across the Willamette Valley and western Portland/Vancouver metro away from the Gorge. Low clouds will likely linger the entire day for the southern Willamette Valley and possibly the central valley too. Used the NBM 90th percentile to boost the cloud cover forecast for the Willamette Valley during that time to better reflect the overcast conditions expected. The persistent fog and/or low clouds will lead to chilly daytime high temps in the upper 30s to lower 40s for most of the central/southern valley and mid 40s elsewhere. Lowered high temps in the central/south valley Monday and Tuesday by nudging towards the NBM 10th percentile. Temps will be a bit warmer at the coast, generally in the low to mid 50s. For those of you who will be in or near the western Columbia River Gorge, expect east winds to return. This will keep fog away and temps slightly warmer, however wind will make it feel colder with wind chill temps dropping into the mid to upper 20s. Used the NBM 90th percentile for forecast winds and wind gusts in the western Gorge and eastern Portland/Vancouver metro to increase winds and better reflect topographical effects. While the KTTD-KDLS pressure gradient never looks to exceed -3 to -6 mb (depending on what model you look at), suspect winds will be slightly stronger than typical for a pressure gradient of this strength due to the strong temperature inversion and stable conditions that will in place. Currently suspect wind gusts up to 50 mph in Corbett and 30-35 mph in Troutdale. It is worth noting winds will not be as strong as the last round of east winds, and the duration of windy conditions will be shorter. This is due to a fairly quick return to onshore flow late Wednesday into Thursday, which is discussed below in the long term discussion. -TK .LONG TERM...Wednesday through Saturday night...Ensemble guidance is generally in good agreement with regards to how the upper-level pattern will progress for the middle to end of next week but a fair amount of uncertainty is present trying to resolve the finer details. The ridge of high pressure is expected to at least flatten to start Wednesday with a broad upper-level low in the Gulf of Alaska nudging southeastward. Almost all ensemble guidance show an attendant cold-frontal boundary then beginning to push either towards or into the Pacific Northwest as Wednesday progresses but many of the grand ensemble members differ on exact timing. This introduces forecast uncertainty as to when dry weather will end and the upper level flow pattern will become zonal. The latest cluster analysis reveals around a 20% chance for rain beginning Wednesday morning, a 25% chance rain holds off until Wednesday afternoon, and a 55% chance rain holds off until late Wednesday night or Thursday. NBM 6-hr PoPs reflect this well by peaking Thursday at 65-80%. Chances for rain then remain in the forecast on Friday and Saturday. The good news is rain amounts do not look high enough to warrant any hydro concerns, temps look to be seasonable, and the Cascades will continue to see more snow. There is also the potential for breezy south to east winds on Saturday (south in the Willamette Valley, east in the western Columbia River Gorge and eastern Portland/Vancouver metro), however model spread is large with a 25-30 mph difference between the NBM 10th-90th percentile for 24-hr max wind gusts. This is due to uncertainty regarding the exact strength, track and timing of a surface low that looks to be somewhere over the northeast Pacific around that time. Despite the high uncertainty, there is a 15-30% chance for max wind gusts over 40 mph from 10pm Fri-10pm Sat according to the NBM, except a 60-70% chance for the coast, western Columbia River Gorge, eastern Portland/Vancouver metro, and high Cascades. Chances for wind gusts over 55 mph are generally under 5%, except 25-35% for the coast and western Gorge.-TK/Schuldt && .AVIATION...Post-frontal showers continue over most of the area, mainly north of KSLE. Expect these showers to end around 00Z Monday. Overall, mostly VFR conditions through the TAF period, with MVFR conditions at times (15%-30% chance of MVFR conditions at every hour). Expect generally southerly winds with the exception of locations within the Northern Willamette Valley which will see east/northeast winds. While winds will likely keep the area mostly clear of IFR/LIFR fog, it still could manifest within the Southern and Central Willamette valley (KSLE and KEUG) as well as secluded, inland areas (KUAO and KHIO). PDX AND APPROACHES...VFR with a 20-40% chance of MVFR conditions through the TAF period. Vicinity showers will come to an end this around 00Z Monday. /42 && .MARINE...Winds begin to decrease this morning as seas continue to build to 14 to 17 ft at 14 seconds for today. Hazardous seas conditions are expected to continue through today, therefore the Hazardous Seas warning will remain in effect until 7PM today. As this front fully dissipates late today, high pressure will build in starting Monday afternoon. This ridge will cause winds to shift to the east-southeast. Areas near the coastal gaps and Columbia River Bar may experience locally elevated winds. Seas will slowly fall, remaining as Small Craft seas until Monday morning, then falling below 10 ft thereafter. Seas will then remain around 6 to 8 ft that 12 seconds until Wednesday. Another weather disturbance will arrive Thursday. ~Hall/Muessle && .BEACH HAZARDS...As a front has passed, elevated seas remain through today. With these seas increasing to 13-15 feet and a long period 14 second swell, there is a high risk for Sneaker Waves today. These waves have the capacity to rush up further inland along beaches with a lot of power. They can easily dislodge logs, and sweep people off of their feet. Be sure to monitor the ocean swells, keep animals and children close, and be cautious if exploring jetties. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Winter Weather Advisory until 4 PM PST this afternoon for ORZ126. WA...Winter Weather Advisory until 4 PM PST this afternoon for WAZ211. PZ...Hazardous Seas Warning until 7 PM PST this evening for PZZ210- 251>253-271>273. Small Craft Advisory from 7 PM this evening to 7 AM PST Monday for PZZ210-251>253-271>273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland x.com/NWSPortland

447 FXUS66 KMFR 081624 AFDMFR Area Forecast Discussion National Weather Service Medford OR 824 AM PST Sun Dec 8 2024 .DISCUSSION...Main update this morning was to pull back the expiration time of the Dense Fog Advisory. Conditions have improved for many valleys west of the Cascades, but webcams show that areas of low visibilities continue east of the Cascades and over some of the major highways. Instead of having the advisory go until 1 pm PST, will let it expire at 10 am or earlier if needed. Otherwise, the rest of the forecast remains on track and no other updates are needed. Skies should clear for most areas by this afternoon, leading to a seasonable day with sunshine for most. We`ll be going back in a pattern very similar to that of last week with cold temperatures and persistent fog/freezing fog in the valleys and sunshine and warm temperatures outside of the valleys. This pattern will continue through mid-week, before a more appreciable change in the weather arrives and continues into the following week. For more details, see the previous discussion below. /BR-y && .AVIATION...08/12Z TAFS...Ceilings and visibilities are fluctuating over most area terminals this morning. Roseburg has stayed at LIFR, while Medford and Klamath Falls have bounced around between MVFR, IFR, and LIFR. North Bend looks to have settled at VFR. Building high pressure will keep widespread clouds from building over northern California and southern Oregon, although ceilings may persist in low-lying areas. Clear skies will help fog return to low- lying areas this evening into early Sunday morning. Other areas should remain at VFR through the TAF period. -TAD && .MARINE...Updated 800 AM PST Sunday, December 08, 2024...Even with Saturday`s cold front out of the area, steep westerly swell will continue to build in area waters. Additionally, a thermal trough will bring gusty northerly winds to waters south of Bandon this afternoon and evening. These conditions are expected to support steep seas in all waters through Monday afternoon. Below advisory seas are expected from Monday afternoon and through most of the week. Long-period westerly swell will move into area waters early Tuesday morning and continue through Tuesday evening. Local areas of steep seas are possible, but an advisory is not currently needed. Active weather remains in the forecast for the end of the week, with gusty winds and steep seas possible over the weekend and beyond. King tides may also play a role in marine conditions over next weekend. -TAD && .PREV DISCUSSION... /Issued 404 AM PST Sun Dec 8 2024/ DISCUSSION... Overview: For the most part, we will have a break in precipitation starting today with only small chances for isolated showers over northwestern parts of the forecast area (e.g. Douglas County). Not expecting much rainfall from these this afternoon. Fog and freezing fog will be the main concerns for weather impacts over the next few days. Our next chance for widespread precipitation will start Thursday morning and continue through the weekend. Otherwise, seasonable temperatures expected through this stretch with occasional breezy wind speeds. Further Details: We will transition towards a long wave trough over the CONUS today/tonight. This will engulf the CONUS for the next few days until the next Pacific trough disturbs this pattern. There are inconsistencies between models and the handling of the next trough, but the general consensus is a troughing pattern over the PacNW through the weekend starting Thursday. The NBM essentially has PoPs over most of the area starting Thursday morning, and this continues through the weekend. The problem is we will likely see breaks in precipitation through this stretch, so there will likely need to be changes to the extended forecast to account for these timing and coverage details. For now, too much inconsistency exists to be certain on changes in the extended, but there will likely need to be changes beyond Thursday to better account for timing so please stay tuned. Saturday into Sunday could be the most impactful day(s) in the forecast outside of fog/freezing fog. This system will be coming in on top of King Tides, so we may have river/creek and coastal impacts slightly exaggerated in association with the King Tides. The probability for 1.00" or greater of rainfall over 24 hours will be around 30 to 60 percent for westside areas Saturday into Sunday. Chances are highest across Curry County and southern Josephine County where these probabilities are 50-60 percent at this time. Regarding snowfall through this same stretch, the probability for 6.0" or more over 24 hours will be around 50-60 percent for both the Cascades (around Crater Lake area) and areas around southern Siskiyou County including Mount Shasta and the Marble Mountains. The latter of which could create impacts over roadways and passes next weekend. Cascade snowfall may be too high in elevation for impacts, but we can reevaluate this in the coming days given the inconsistencies between long range models. -Guerrero && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Dense Fog Advisory until 10 AM PST this morning for ORZ021>024- 026-028>031. Beach Hazards Statement from Monday evening through Tuesday afternoon for ORZ021-022. CA...Dense Fog Advisory until 10 AM PST this morning for CAZ080-081- 083>085. PACIFIC COASTAL WATERS...Small Craft Advisory until 1 PM PST Monday for PZZ350-356-370-376. && $$ MNF/JWG/TAD

570 FXUS66 KEKA 081219 AFDEKA AREA FORECAST DISCUSSION National Weather Service Eureka CA 419 AM PST Sun Dec 8 2024 .SYNOPSIS...High pressure is building in today bringing breezy northerly winds and clearing skies. Lighter winds and clear skies are expected Monday and Tuesday. Wednesday may see some increasing clouds with chances for rain Thursday and Friday. Saturday a stronger storm system is possible. && .DISCUSSION...High pressure is building towards the west coast this morning as the upper level trough in the Pacific Northwest moves inland. Widespread fog and low clouds are in place across many of the valleys this morning. Some of it is likely dense, but confidence is low on exactly where. These low clouds are expected to clear out this morning. Northerly winds are expected across the area with 10 to 20 mph winds along the coastal areas and over the higher terrain. Tonight there will be some fog in the interior valleys, but it is expected to be more limited and more likely to be in the northern areas as drier air moves in. Winds will become northeast and help keep the coastal areas clear overnight. Monday is expected to see mainly clear skies and dry conditions. Highs are expected to warm into upper 50s to mid 60s. Some of the Trinity River valleys that see fog overnight may be slow clear and see temperatures only warm to around 50. Monday night and Tuesday conditions are expected to be fairly similar to the previous day. Wednesday the ridge starts to flatten and the flow becomes more zonal. The clusters are showing different solutions with the main difference being how flat the ridge gets which translates to how far south the precip is expected to make it Wednesday night and Thursday. Two of the clusters bring some light rain all the way down to Lake county while the other two keep it farther north. Even the wetter solutions keep totals under an inch in the north through 4pm Thursday. Chances of rain increase on Friday, but amounts generally still remain below an inch. Friday night into Saturday the potential for a stronger storm increases. The probably over 1 inch increases to around 35 to 55 percent. Tho majority of the ensembles now show a fairly strong system. This weather system will also likely bring strong winds. Currently the NBM is showing a 30 to 70 percent chance of wind gusts exceeding 40 mph on Saturday, but this is mainly limited to Humboldt and Del Norte counties with lighter wind elsewhere. In Trinity county this could come with lower snow levels possibly impacting highway 299. At this point all we can say is this is a possibility shown in some models, but confidence is low on it. MKK && .AVIATION...MVFR to IFR ceilings are possible for coastal terminals into the mid morning. Beyond that, VFR conditions are forecast and northerlies will begin to pick up today as high pressure builds into the area. It could be particularly gusty around KCEC with potential gusts from 15 to 20 knots. Periods of MVFR visibilities could affect Ukiah into the morning, but VFR conditions are expected through the day. && .MARINE...Advisory level northerlies are expected to continue into Monday morning. Winds are forecast to peak this afternoon with gusts of 25-30 kts possible nearshore and gales possible in the lee of Cape Mendocino. Steep wind waves will be associated with these winds. At the same time, a large mid-period westerly swell will build in, increasing significant wave heights to 14 to 15 ft. Conditions will improve into early this coming week. JB && .BEACH HAZARDS...A long period westerly swell is forecast to fill in Tuesday, peaking around 8 ft at 16 seconds. This will result in a moderate risk of sneaker waves Tuesday into early Wednesday. Be cautious visiting beaches and jetties Tuesday, as relatively large and unexpected waves could sweep in without warning. Stay much farther back from the water and never turn your back on the ocean. There is, also, a possibility for coastal flooding late this coming week and into next weekend. Southerly winds are forecast to pick up and accompany a period of higher tides. When this occurs at the same time, it makes coastal flooding more likely. More details on coastal flooding will be available when models come into better focus. JB/JLW && .EKA WATCHES/WARNINGS/ADVISORIES... CA... None. NORTHWEST CALIFORNIA COASTAL WATERS... Small Craft Advisory until 3 PM PST Monday for Pzz450-455- 470. Small Craft Advisory until 3 AM PST early this morning for PZZ475. Gale Warning until 9 PM PST this evening for PZZ475. && $$ 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

749 FXUS66 KMTR 081843 AFDMTR Area Forecast Discussion National Weather Service San Francisco CA 1043 AM PST Sun Dec 8 2024 ...New AVIATION... .SYNOPSIS... Issued at 204 AM PST Sun Dec 8 2024 Slightly cooler conditions today before breezier conditions begin on Monday. Chilly temperatures are expected Monday and Tuesday morning with widespread inland lows in the 30s. Chances for light rain increase midweek, with the best chances for accumulating rain Friday into the next weekend. && .UPDATE... Issued at 959 AM PST Sun Dec 8 2024 Mix of foggy and hazy conditions have been reported through the Bay Area this morning. Satellite shows fog starting to dissipate within the North Bay while hazier conditions persist over the South and East Bay. We are still seeing some reduced visibilities across the Bay Area from fog/haze so drivers are advised to leave extra time to reach their destinations and to slow down. Fog/haze should continue to dissipate through the remainder of the morning as temperatures warm and increased mixing is able to occur in the lowest levels of the atmosphere. Otherwise the forecast remains on track. Winds are expected to strengthen slightly this afternoon before gusty offshore flow returns to portions of the Bay Area on Monday. && .SHORT TERM... (Today and tonight) Issued at 204 AM PST Sun Dec 8 2024 High clouds, haze, and patches of fog blanket the region as a weak cold front comes through the region. No appreciable precipitation is expected tonight, as low temperatures drop into the low to mid 40s in the coldest interior valleys, up to near 50 along the coast. High clouds will clear out through the day, but linger into the evening hours, contributing to a slightly cooler day today with the interior valleys reaching the upper 60s, with the coastal and Bayshore regions seeing highs in the lower to middle 60s and the higher elevations in the middle to upper 50s. && .LONG TERM... (Monday through Saturday) Issued at 204 AM PST Sun Dec 8 2024 Later on Sunday into Monday, a shortwave trough over British Columbia deepens as it digs into the intermountain West, combining with a high pressure system over the Great Basin to create favorable conditions for gusty offshore winds in the North Bay interior Mountains, East Bay Hills, and Santa Cruz Mountains. Gusts in the North Bay interior mountains reach 30-40 mph, especially in eastern Napa County, while those in the East Bay and Santa Cruz Mountains reach 20-30 mph. Widespread fire weather concerns are not expected, although dry conditions continue in the interior Central Coast. Clear skies will return to the region as upper level ridging takes hold. High temperatures remain relatively similar through the midweek, with a slight cooling across the North Bay into the northern San Francisco Bay Area on Tuesday. With the clear skies promoting more radiational cooling late Monday into Tuesday, low temperatures reach the low to mid 30s in the inland valleys, with the coldest temperatures taking hold in the Sonoma County valleys and southern Monterey County; temperatures below freezing are expected in areas close to the border with San Luis Obispo County. Confidence in the necessity of a Frost Advisory continues to increase, and one is likely to be issued sometime later today. Low temperatures will warm up through the rest of the week as high clouds return to limit radiational cooling. The forecast looks a lot more interesting towards the latter part of the week as rain chances reenter the picture. Some scattered rain chances arrive later Wednesday into Thursday, with the possible arrival of a shortwave trough. Confidence is quite low, given that the European ensemble model mean shows the shortwave coming into the West Coast, while the American and Canadian ensemble means showing zonal flow continuing through the period. In contrast, confidence is increasing for an upper level low coming to the western United States on Friday into the next weekend. It`s a little too far out to place much faith in forecast storm totals, but as things stand, significant rainfall is possible across the North Bay. Speaking probabilistically for a moment, for the period from 4 AM Friday to 4 AM Sunday, there`s a 40-60% probability of at least 1 inch of rain across the North Bay, with the highest probabilities in the higher elevations of Sonoma and northern Napa Counties, while probabilities for 1 inch of rain across the northern San Mateo Peninsula, the Santa Cruz Mountains, and the Santa Lucia range range from 20% to 40%. It`s a good reminder that we are entering the climatic peak of our rainy season, and to expect more storms as the pattern gets more active. && .AVIATION... (18Z TAFS) Issued at 1043 AM PST Sun Dec 8 2024 Across the Bay Area, vis ranges from VFR to IFR due to haze and fog. Where winds have begun to pick up, conditions have improved some; however, where the inversion has not mixed out, visibility remains reduced. The ADJLAV seems to have tracked this best so far this morning, which was used to help time the mixing, increase in winds, and visibility improvement. Though if winds remain light to non- existent, visibilities may stay reduced this afternoon and evening. Moving on to tonight, expect KSTS and KAPC to tank again in terms of vis and cigs thanks to fog development. Near SFO and the surrounding terminals, KHAF, KOAK, KLVK, and KSJC, guidance shows we could see a repeat of lower vis overnight and into late tomorrow morning. This would be reliant on how quickly the offshore winds develop. Vicinity of SFO...Webcams and KSFO show lingering haze near and around KSFO this morning. The question becomes, when will the winds increase enough to mix this out? Latest thinking is that we may see vis bounce around for a few hours, but not improve to VFR until closer to 21Z. Confidence is medium on timing of improvement. SFO should be VFR this evening and during the overnight hours. Tomorrow morning there is some uncertainty in the forecast. Should winds remain light and moisture elevated, guidance shows the possibility of reduced vis tomorrow morning. Confidence was too low to add any hints of that at KSFO. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR conditions are expected for the next 24 hours. Guidance shows the winds should hold at KSNS and keep them at VFR, but as previously noted, haze could pop up later this afternoon. && .MARINE... (Today through Friday) Issued at 959 AM PST Sun Dec 8 2024 Strong northerly winds and rough seas will continue through the day. Winds will decrease substantially overnight, allowing seas to abate by mid-day Monday. Gentle, shifting wind and a moderate NW swell will persist through the remainder of next week. && .MTR WATCHES/WARNINGS/ADVISORIES... CA...Frost Advisory from midnight Monday night to 9 AM PST Tuesday for CAZ506-510-513>516-518-528. PZ...Small Craft Advisory until 9 AM PST Monday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM. && $$ SHORT TERM...DialH LONG TERM....DialH AVIATION...KR MARINE...KR Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea

229 FXUS66 KOTX 081758 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 958 AM PST Sun Dec 8 2024 .SYNOPSIS... A weather system will bring moderate to heavy mountain snow to the Cascades and mountains of north Idaho today. The weather will be seasonably cold and dry Monday and Tuesday. A series of disturbances will bring periods of mountain snow and valley rain or snow Wednesday afternoon onward. && .DISCUSSION... Today: The Inland Northwest experienced a break in the precipitation most of the night, but will see a return of snow and rain prior to sunrise this morning. As of 3 AM, a cold upper trough over Vancouver Island was crossing the Washington Cascades. Regional radar and WSDOT web cameras showed heavy snow along the Cascade Crest, and the High Resolution Ensemble Forecast (HREF) suggests snowfall rates in excess of an inch per hour through 9 AM for Stevens Pass. A Winter Storm Warning remains in effect through 4 PM for the mountainous terrain of western Chelan county for an additional 6 to 10 inches of accumulation with the heaviest snow occurring this morning. A Winter Weather Advisory is in effect for the mountains of the Central Idaho Panhandle including Lookout Pass on Interstate 90 where 5 to 10 inches are expected by the end of the afternoon. A Winter Weather Advisory is also in effect for elevations above 4000 feet for Garfield and Asotin counties where 2 to 5 inches will accompany west winds gusting as high as 40 mph over terrain exposed to west winds. Our lowlands will also have a quick shot of light snow today. The opportunity for accumulation will be brief from mid morning into early in the afternoon for the valleys of the Idaho Panhandle and adjacent portions of Washington. The probability of an inch of accumulation will be less than 20 percent for the Spokane metro, Sandpoint, Kellogg, and Pullman. The Camas Prairie above 3500 feet will receive accumulations up to two inches around Winchester and Craigmont. Tonight: Periods of light snow will be mainly limited to the the southern and central Idaho Panhandle and parts of far southeast Washington tonight. Dry and cold northerly flow aloft should disperse low clouds from north central Washington and some of northeast Washington overnight. Places that clear out will likely dip into the teens by Monday morning including places like the Methow Valley, Republic, Colville, and Metaline. Lows in the 20s will be common elsewhere including the Columbia Basin, central Washington, Spokane metro, and most of north Idaho. Monday and Tuesday: A sharp upper level ridge will build along the Washington/Oregon coast Monday and Tuesday bringing dry and stable weather to our region. The HREF holds onto a low cloud deck over the central and southern Idaho Panhandle, Palouse, and Spokane area Monday and spreads it into the Columbia Basin and valleys of northeast Washington and north Idaho Monday night into Tuesday. Light boundary layer flow out of the south suggests that any low clouds that aren`t scrubbed out today and tonight will likely expand Monday night and Tuesday. Even high resolution models struggle with cloud layers near the ground, so this scenario is low confidence. But if the low clouds develop Monday and Tuesday, folks under this low cloud deck will experience a raw and chilly day with highs only reaching the mid 20s to low 30s. Our air mass early this week is colder than what we experienced most of last week. /GKoch Wednesday through Saturday: Other than being in general agreement that the Pacific Northwest will trend toward an unsettled weather pattern, there is a high degree of uncertainty on how the weather will evolve for the latter half of the week. For Wednesday and Thursday, ensembles have backed off on the precipitation potential with 65% of ensembles from the ECMWF, GEFS, and Canadian suites holding on to some degree of an upper level ridge into Thursday. Examining their deterministic counterparts, the latest GFS shows a weak wave moving through on Thursday with primarily mountain snow. Meanwhile the ECMWF depicts an amplifying ridge over the Inland Northwest on Thursday as an upper level trough approaches the west coast and then moves through on Friday. These significant differences result in a very low confidence forecast for the Wednesday through Friday timeframe. Given the expected moist boundary layer and widespread stratus/fog conditions early week, any ripple in the upper level flow would be enough to produce light precipitation for the lowlands. This will continue to be monitored over the upcoming days. For the weekend, there does seem to be slightly better agreement that a stronger system will move into the Pacific Northwest although the specific details in the exact strength and track does remain uncertain. Despite the high uncertainty, this will be the period to watch for the potential for heavy mountain snow and widespread light lowland snow. Right now, the NBM is giving the Spokane area, the Okanogan Valley, and Wenatchee area about a 20 to 30 percent chance for 1 inch of snow for Saturday and Sunday. /vmt && .AVIATION... 12Z TAFS: Precipitation this morning is limited to near the Cascade crest, extreme eastern Washington, and north Idaho and will diminish into the afternoon hours. Models try to quickly redevelop fog and low stratus tonight for the Columbia Basin, Spokane area, and other northern valleys. The general expectation is fog to form in the Palouse this evening near Pullman and spread north and west into the Columbia Basin and Spokane area overnight. Differentiating fog and low stratus is quite challenging from a forecast perspective but the current thinking is SCT low stratus for Lewiston and OVC low stratus for Coeur D`Alene and Pullman. FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: The forecast for the low cloud deck is a low confidence forecast. The wind in the 1500 to 4000ft layer that helped disperse clouds the last 12 hours will weaken through the day and overnight suggesting the redevelopment of fog and low clouds, but our inversion under the cold upper trough won`t be nearly as strong as the inversion that locked low clouds over the Inland Northwest all last week. Stratus under weak inversions sometimes develops in several layers before high pressure arrives and stabilizes the air mass. So, as the surface winds diminish tonight, we may see some places in north Idaho and the eastern third of Washington experience fog while other nearby locations have a 1500-3500ft cloud layer. And other spots may bounce between multiple cloud layers until Monday night when high pressure begins to strengthen. ----------------------- 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 26 32 26 33 26 / 40 0 0 0 0 0 Coeur d`Alene 36 27 33 25 34 25 / 70 10 0 0 0 0 Pullman 37 28 35 24 36 26 / 70 40 0 0 0 10 Lewiston 45 32 42 27 39 30 / 50 30 0 0 0 0 Colville 35 17 31 17 31 20 / 30 0 0 0 0 10 Sandpoint 35 26 32 25 34 24 / 70 10 10 0 0 10 Kellogg 35 27 33 25 36 27 / 100 30 10 0 0 10 Moses Lake 39 22 34 23 32 26 / 10 0 0 0 0 0 Wenatchee 41 28 34 23 30 29 / 10 0 0 0 0 0 Omak 35 23 32 20 29 25 / 10 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 4 PM PST this afternoon for Central Panhandle Mountains. WA...Winter Weather Advisory until 4 PM PST this afternoon for Northeast Blue Mountains. Winter Storm Warning until 4 PM PST this afternoon for Western Chelan County. && $$

597 FXUS66 KPDT 081743 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 943 AM PST Sun Dec 8 2024 Updated Aviation Discussion .AVIATION...18Z TAFs...VFR conditions expected to begin the TAF period. Winds breezy this morning through early afternoon with gusts 20-30 knots all sites except YKM. Tonight through tomorrow morning light winds with VFR CIGs and VIS expected initially. Fog/mist and low clouds may begin redeveloping, with most likely locations YKM and ALW. Sites ALW and PDT have a level of uncertainty though regarding potential fog and low stratus due to southerly winds expected overnight and into the morning. For now have put low stratus at ALW alongside mist and left PDT out of low stratus and fog. Finally, uncertainty with fog development at PSC, so have utilized VCFG for now, but will refine this to likely or unlikely fog later this afternoon with next update based on ongoing trends and latest forecast updates. Goatley/87 && .PREV DISCUSSION... /issued 317 AM PST Sun Dec 8 2024/ SHORT TERM...Sunday through Tuesday... Bottom Line Up Front 1. Mountain snow through Sunday afternoon. 2. Return of high pressure will bring stagnant air, fog and low cold temperatures, stratus back to the area. Current nighttime satellite shows some freezing fog lingering around Yakima proper and the adjacent valley area. A special weather statement has been issued for the area so be advised and drive with caution. Satellite also shows some low clouds lingering over the Northern Blues with a few spotted areas in Kittitas as well. Otherwise, clear skies can be seen across the vast majority of the region thanks to the upper level system that began to makes its way across the region today. The leading edge of the system was able to scour out the cold pool allowing clear skies to return. The break in the system will however be short lived as models are in firm agreement showing the back edge of the upper level system has already begun to swing its way into the Cascades. This portion of the system will continue to bring precipitation to the mountains and coupled with the orographic lift and the moisture, will lead to some heavier snow showers through the day. Hence the Winter Storm Warning already in place now through 4 PM Sunday afternoon for the WA Cascades and then the Northern Blues. Over 80% of the raw ensembles for the HREF are in agreement with over 10 inches of snow accumulation across the WA Cascades as well as along the Northern Blues above 4500 feet. Mainly Tollgate to Ski Bluewood, however, the I-84 corridor will see between 4 to 8 inches. Models show the precipitation to dwindle after 4 PM with only some scattered showers remaining through the evening. Right on the heels of the system, a strong upper level ridge will make its way back over the region. Clusters show very strong agreement with the ridge beginning to push its way onshore Sunday night before settling over the region by Monday morning. Northwest flow aloft will bring in yet another cold pool, shut off the winds and leave the region under stagnant air. NBM shows temperatures will again dive into the upper 30s with a few isolated locations along the foothills seeing the low 40s. With this set up, the region will once again be under the influence of the daily inversion which will lock the region in with stratus and areas of fog will return. Especially through the Valleys and the Basin. Confidence in the return of stratus and fog is high (80%+). Bennese/90 LONG TERM...Wednesday through Saturday...The extended period begins with a ridge over the Pacific Northwest. However, this ridge will move eastward on Wednesday as a weakening upper trough and cold front approach. THese features will move across the area Wednesday night into Thursday and bring precipitation. The deterministic guidance keeps Friday mainly dry, while the NBM does not. By Saturday, a stronger low looks to be approaching the coast somewhere between British Columbia and the Washington and the associated trough and cold front will move onshore in the Pacific Northwest bringing another round of precipitation. Where the precipitation falls and how much will be dependent on the strength and location of the low, and there is considerable uncertainty with that at this time. Latest model guidance has slowed down the precipitation with the Wednesday system, so have backed off POPS a bit during this period. By Thursday still have slight chance to chance over most of the region, though higher POPS across the Cascades. Liquid equivalent QPF looks to be on the lighter side, with no more than a few hundredths in most places on Wednesday and maybe up to 0.10 in the higher peaks of the Cascades. On Thursday, QPF is still fairly light, with a few hundredths over much of the higher terrain and 0.10 to 0.20 liquid equivalent across the Blue Mountains and up to 0.30 to 0.50 across the Cascades. THis will translate in perhaps a few inches of snow. Snow levels will range from around 200-2500 feet in the north to 3500-4000 feet in central Oregon. By Saturday, the ensemble clusters are favoring the more amplified ECMWF solution (39%), though even in the clusters there are a range of solutions from a trough in the west to a ridge. && .PRELIMINARY POINT TEMPS/POPS... PDT 45 28 42 23 / 40 40 0 0 ALW 45 32 41 25 / 50 40 0 0 PSC 49 29 38 27 / 20 20 0 0 YKM 47 24 40 22 / 20 0 0 0 HRI 49 30 39 26 / 20 20 0 0 ELN 45 26 38 22 / 20 0 0 0 RDM 42 19 41 19 / 0 0 0 0 LGD 40 27 37 20 / 80 60 0 0 GCD 40 27 38 18 / 40 50 0 0 DLS 50 32 42 29 / 30 10 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Winter Storm Warning until 4 PM PST this afternoon for ORZ502. WA...Winter Storm Warning until 4 PM PST this afternoon for WAZ030- 522. && $$ SHORT TERM...90 LONG TERM....77 AVIATION...87

401 FXUS65 KREV 080909 AFDREV Area Forecast Discussion National Weather Service Reno NV 109 AM PST Sun Dec 8 2024 .SYNOPSIS... * A dry cold front will bring cooler temperatures for Monday with a period of gusty northeast to east ridge top winds. * After high pressure ridge briefly returns Tuesday, another weak weather system will begin to displace this ridge by midweek. * Some signals for a wetter storm system by next weekend, but confidence is low on exact timing and impacts. && .DISCUSSION... Latest web cameras show no fog around Susanville or along US-395 near Honey Lake. The KSVE airport was reporting visibility of 3-5 miles and with a swath of cirrus moving overhead, the potential for significant freezing fog redeveloping through this morning is low (less than 20%). While the initial trough passage on Saturday helped to flatten the persistent ridge, a back door dry cold front passage tonight into Monday will shift winds to north and northeast, and also bring cooler highs only in the upper 30s-lower 40s for Monday. The latest track of the upper low associated with this front takes it farther east more quickly, resulting in a shorter period of gusty NE-E Sierra ridge top winds from Monday morning-evening, with peak gusts near 55 mph. While a high pressure ridge may bring back inversion conditions and patchy fog Monday night and Tuesday in similar areas of northeast CA/northwest NV that received fog last week, lesser coverage and persistence is expected. By midweek, the transition to a more progressive pattern begins with a weak shortwave falling apart as it reaches the Sierra. Although this system only brings minimal precipitation chances and only a modest uptick in winds, it will help displace the high pressure ridge that produced the largely stagnant weather pattern since Thanksgiving. Looking ahead to next weekend, medium range guidance still opens the storm door for a Pacific weather system reaching the Sierra. The latest blended guidance continues to lean toward 0.50-1.0" of liquid near the crest, which would correspond to about 6-12" of snowfall for the higher elevations and main Sierra passes. The more aggressive scenarios have eased back to 2-3" liquid along the crest (down about 1" from yesterday), but only about 10% of the ensemble scenarios currently support these higher-end totals (yielding 2 or more feet of snow near the crest). While Tahoe basin areas could still see snowfall exceed any of November`s storms, it wouldn`t surpass them by very much, with a slight majority (50-60%) of the blended guidance projecting 3-6" down to lake level. The limiting concern from this latest batch of guidance is a more northerly storm track favoring the Pacific Northwest. This would leave only the southern edge of moisture reaching the Sierra from Tahoe northward, with even less snow reaching Mono County and limited precip (but increased winds) spreading into western NV. Snow levels aren`t as low in western NV with these projections, coming in around 5000-5500 feet for Saturday but snowfall amounts in this scenario would be rather sparse. There`s another potential storm in line for the December 16-17 time frame, but again confidence is lower on whether it takes more direct aim at the Sierra or tracks farther north. MJD && .AVIATION... VFR conditions with generally light winds will prevail through midweek, although increasing NE-E FL100/ridge top winds with gusts to 45 kt will produce increased turbulence near/west of the Sierra crest from Monday morning through Monday evening. At KSVE, MVFR visibility of 3-5 SM has been observed but no ceilings reported since 06Z. The potential for IFR/LIFR conditions with FZFG through 18Z is low, only about 10-20% chance. MJD && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$

854 FXUS66 KSTO 080913 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 113 AM PST Sun Dec 8 2024 .SYNOPSIS... Slightly cooler and breezier weather enters the area today through Tuesday. Dry weather continues through mid-week before unsettled weather potential returns towards the end of the week. .DISCUSSION... Low visibilities are once again being observed around the southern Sacramento and northern San Joaquin Valley`s this morning. At the time of this discussion, Mather and McClellan AP`s were reporting visibilities down to 1/4 mile, while Stockton and Modesto AP are down to 1.25 and 2.0 miles, respectively. A Dense Fog Advisory is once again being considered for the southern Sacramento and northern San Joaquin Valley`s. A slight shift in the upper level wind pattern will occur today and winds will increase, and as a result fog development should be mitigated from widespread to isolated, tomorrow morning. A shortwave is forecast to move through the PacNW today and slightly lower our heights, and orientate them into a north to south gradient. We should see wind speeds begin to pick up later this morning, which will help clear the stagnant air around the area. Northerly winds will be the strongest along the I-5 corridor and in the foothills and mountains in the canyons and gaps. The National Blend of Models (NBM) currently showcases around a 30-60% chance of wind gusts reaching at least 30 mph or more along the I-5 corridor today and around 40-90% chance tomorrow along I-5 and in the foothills and mountains. As a result of the slightly lowering heights and northerly winds, resultant high temperatures will lower tomorrow into the low to mid 60s for the Valley. Wind gusts should weaken Tuesday afternoon, and temperatures will once again slightly fall into the mid to upper 50s across the Valley, with cooler upper 30s to low 50s for the higher elevations. The shortwave will continue to translate eastward into the northern Great Plains Tuesday and Wednesday, and ridging will rush in and build across our area and help keep us dry and sunny for the middle of the work week. Surface winds will remain from the north, although be much lighter with speeds generally less than 10 mph across the Valley floor. .EXTENDED DISCUSSION (Thursday THROUGH Sunday)... Ensembles continue to paint a trough beginning to develop in the Gulf of Alaska by Thursday and dig into northern California by the end of the week. The most recent run of the NBM has backed down on potential snow amounts for the northern Sierra and Southern Cascades, with probabilities of seeing around a foot of snow from the system have decreased to around 50% by Sunday afternoon. The changes in probabilities are related to the discrepancies in strength of the trough, track, and snow levels, which Cluster Analysis is still showing differing solutions. Snow levels according to the NBM remain roughly around 5000 feet and higher, although trends have shown a slight increase in elevation for higher snowfall totals. Rainfall totals remained relatively unchanged however, with around a 40 to 75% chance of 1 inch of rainfall or more for NorCal, with the highest probabilities in the Sierra and Southern Cascades, and from Redding northward. While details remain fuzzy this morning regarding track and potential precipitation impacts, confidence in a wet end-of-week and weekend continue to increase. With this system, high temperatures are forecast to fall into the mid to upper 50s and low 60s for the Valley. Stay tuned to the forecast for updates as we move through the week and details become more clear. && .AVIATION... Areas of MVFR with local IFR/LIFR possible in BR/FG in the Southern Sacramento and Northern San Joaquin Valleys through 18Z-20Z Sunday. Otherwise, VFR over interior NorCal next 24 hours. Northerly wind gusts 15 to 25 kts in the Sacramento Valley and through the Delta after 12Z-15Z Sunday. Northeast to east wind gusts 20 to 30 kts in the foothills/mountains, mainly after 06Z Monday. Elsewhere, surface winds less than 12 kts. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$

868 FXUS65 KMSO 081829 AFDMSO Area Forecast Discussion National Weather Service Missoula MT 1129 AM MST Sun Dec 8 2024 .DISCUSSION... KEY MESSAGES: - Snow showers have formed across the region this afternoon and may put down a quick few inches of snow in isolated locations. A quick moving Pacific cold front scoured out the majority of valley inversions across the Northern Rockies last night. In the wake of the cold front, snow showers are developing this afternoon. The bulk of snow accumulations will be confined to area mountains and mountain passes. A secondary shortwave of energy is moving through the northwesterly flow pattern this afternoon and overnight, that will bring another round of light to moderate snowfall. A cooler air mass is in place at all levels, so the threat for freezing rain or drizzle is not be a concern with this system. Snow-levels will lower to most valley floors in western Montana, and down to 2500 feet in north-central Idaho, including Lemhi county, by Monday morning. Some of the snow showers will be capable of becoming transitory bands this evening after sunset and overnight. These bands are not expected to be overly strong or stationary, though they could still put down a quick 1 to 2 inches. Probabilities for valley accumulations are quite low, around 10%, but isolated areas could see accumulating snow if impacted by one of the bands. The mountains and mountain passes could see anywhere from 3 inches on the low end, to 6 inches on the high end, by Monday morning. Scattered snow showers will remain in the forecast through the day Tuesday, with isolated low impacts to area roads. By Wednesday, a short lived ridge of high pressure will build over the region and will last for about a day and a half. Since the recent cold front has scoured out valley cold pools, it will take time for the next ridge to build up the low level moisture needed for fog, and this ridge won`t be around that long. So we expect fog impacts in the middle of the week to be more isolated and right along the river corridors. Any fog affecting area airports will not persist all day, but will generally break up by early afternoon, if it gets that bad at all. Ensembles agree very well on another short wave coming through Thursday evening causing another round of light mountain snow. And, in general, the pattern remains active with low to moderate impacts from mountain snow through the rest of the extended. && .AVIATION...Conditions are more unstable today behind a cold front from last night. With northwest winds aloft of 25-35 knots, we expect any resulting showers to organize into bands. However, a lack of a stable layer around 10,000 ft means the bands will not be stationary. As a result, any snow impacts from these bands are expected to be short lived and transitory in nature. Terminals KMSO, KHRF, and KBTM are most likely to be affected by showers through 09/05Z. Patchy fog in valleys affecting KGPI and KMSO may occur through mid-morning before dissipating. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...None. ID...None. && $$

141 FXUS65 KBOI 081623 AFDBOI Area Forecast Discussion National Weather Service Boise ID 923 AM MST Sun Dec 8 2024 .DISCUSSION...Satellite imagery at 8 AM MST continues to show fog, in many places dense, in the basins and valleys. 12Z Boise raob showed the inversion much weaker than yesterday but still not scoured at low elevations. We are confident that it will scour around midday (3 PM MST at the latest) for several reasons: Coldest air aloft has not yet arrived but models bring it in around noon. Cooling aloft will increase vertical mixing. MOS statistical forecasts, which depict the fog and stratus nicely this morning, remove it between 11 AM and 2 PM MST (MET MOS is an exception and keeps it until tonight). Finally, models show moderate west/northwest boundary layer winds later today which will help sweep the fog and stratus out. The current Dense Fog Advisory will continue until 11 AM MST, with improvement expected soon after. Remainder of forecast is on track as described below. && .AVIATION...Areas of IFR/LIFR low clouds and fog, clearing 18z to 21z/Sun. Mountains obscured. Scattered snow showers developing this afternoon through this evening. IFR/LIFR fog and stratus may redevelop overnight across the Snake Basin and mountain valleys. Surface winds: W-NW 5-15 kt this afternoon, strongest near KTWF/KJER where gusts 25-30 kt will develop. Winds aloft at 10kft MSL: W-NW 25- 35 kt. KBOI...VLIFR in fog, improving to IFR around 18z/Sun before clearing around 20z/Sun with VFR conditions. 20% chance of snow showers this afternoon and evening. Fog and low clouds redeveloping overnight. Light surface winds, becoming NW 5-10 kt this afternoon. && .PREV DISCUSSION... SHORT TERM...Today through Tuesday night...A cold front has moved through the area with low clouds and fog lingering over the valleys. A dense fog advisory has been issued for the Treasure Valley and Weiser River Basin due to slick roads and poor visibilities. Cooler air will continue to move into the area from the NW this afternoon, which will help clear out the fog and stratus around midday. A weak shortwave moves over the area late this afternoon and evening, with scattered showers developing this afternoon across eastern OR and southwest ID. Showers taper off late this evening as drier air moves in from the NW. A ridge builds over the West on Tuesday with a strengthening inversion. Areas of fog and stratus will develop across the lower elevations below 4000 feet on Tuesday and Wednesday. Temperatures will be within a few degrees of normal, falling to below normal in the fog and low stratus conditions, and above normal in the mountains by Wednesday. LONG TERM...Wednesday through Sunday...Dry weather on Wednesday with a ridge in place, but with increasing mid-high clouds. Ensembles continue to depict an active pattern Thursday through Saturday, but with some deviations. The trough on Thursday appears weaker in the deterministic models, with the GFS/EC/Canadian keeping the track to the north. Though the West Central and Wallowas may see light snow showers, the rest of the area seems drier until Saturday. The Saturday system is the stronger of the two, but is looking to weaken significantly as it moves inland from the Pacific. Precipitation chances on Thursday are still 20-40% through the area despite the deterministic model trends, and on Saturday 30-50% in valleys and 60-70% in mountains. Precipitation amounts are still forecast to be on the lighter side, with a little too much disagreement for a proper range this far in advance. Temperatures remaining within a few degrees of normal. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Dense Fog Advisory until noon MST today IDZ012-014-033. OR...Dense Fog Advisory until noon MST today ORZ064. && $$ www.weather.gov/Boise Interact with us via social media: www.facebook.com/NWSBoise www.twitter.com/NWSBoise DISCUSSION...LC AVIATION.....ST SHORT TERM...KA LONG TERM....JM

673 FXUS65 KLKN 081017 AFDLKN Area Forecast Discussion National Weather Service Elko NV 217 AM PST Sun Dec 8 2024 .SYNOPSIS...Quiet and dry weather will persist early next week with below normal temperatures as a northerly flow pattern sets up over forecast area. A gradual warming trend expected by midweek as high pressure develops, while winds remain light throughout the period. Uncertainty remains in a more active weather pattern returning for late next week. && .SHORT TERM...Today through Monday night Current water vapor satellite imagery shows mid to high level cloud cover as a trough of low pressure is moving across the forecast area. A few light snow showers are expected mainly across the Jarbidge Wilderness area, but probability of significant snow accumulations of an inch is 10 to 20%. The attendant cold front will push southeastward across northern Nye and White Pine Counties during the morning hours today, with no precipitation anticipated given the lack of moisture available. In the wake of the cold front, cooler temperatures are expected, with highs mainly in the upper 30s to the lower 40s across the northern part of the state and upper 40s and lower 50s across the central part of the state. During the day, northwest winds of 10 to 20 mph will bring breezy conditions to central and eastern Elko County. Overnight lows will range from the single digits to the teens under partly cloudy skies. During the day on Monday, the aforementioned trough will move southeast across Utah, while a ridge of a high pressure strengthens along the west coast. Northwest winds of 10 to 20 mph will bring breezy conditions to central and eastern Elko County, and parts of White Pine and Nye Counties. Daytime highs today will be in the lower 30s and mid 40s. Another chilly night is in store, with overnight lows ranging from the single digits to the teens, which will be seven to nine degrees below normal for this time of the year. Apparent temperatures will be near zero degrees in the coldest valleys. With clear skies, light winds, and a strong inversion, patchy freezing fog may develop in the valleys across northern Nevada each night. Any fog that forms is expected to dissipate by late morning. && .LONG TERM...Tuesday through next Sunday Quiet to start the long term period. Upper level ridging and surface high pressure combine for warmer than normal temperatures and light winds (less than 10 mph). That ridging shifts off to the east by Thursday, opening the area to a much less straightforward forecast. Current long term model guidance indicates scattered shower chances across the forecast area starting Thursday and continuing through the end of the forecast. POPs at any given time remain on the low end, peaking at 50% in northern Elko county on Saturday but remaining below 30% for the rest of the period. Additionally, POPs at any given time are highest near the Idaho border and lowest in northern Nye county. PW values during this time remain below 0.3 inches during this period, indicating this system may end up drier than current model guidance. Additionally, theres currently a large amount of conflict in timing and location guidance, which makes it likely these widespread low POPs evolve to higher POPs over a much smaller area. && .AVIATION...VFR conditions will prevail at all terminals through the next 24 hours. Winds this afternoon will gradually shift northerly with speeds generally between 8KT and 12KT, occasional gusts around 18KT. Mid and high level clouds will also dissipate as the upper shortwave progresses east. && .LKN Watches/Warnings/Advisories... None. && $$ 90/94/92