Area Forecast Discussion
Issued by NWS Spokane, WA

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000 FXUS66 KOTX 242256 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 256 PM PST Wed Feb 24 2021 .SYNOPSIS... Another frontal system will bring snow to northeast Washington, the Palouse, and north Idaho on Thursday along with gusty afternoon winds. Windy weather will likely continue into Thursday night and Friday from Wenatchee across the Columbia Basin onto the Palouse. Heavy mountain snow will also fall in the Cascades and Panhandle mountains Thursday into Friday. Quieter weather is expected this weekend. && .DISCUSSION... Tonight: Mostly clear skies this evening will be followed by increasing clouds ahead of our next frontal system. Look for temperatures to tumble quickly this evening which is an important element of the forecast. As precipitation spreads across northeast Washington and the Idaho Panhandle early in the morning, readings in the upper 20s and low 30s will set the stage for morning snow in places like Spokane, Coeur d`Alene, Sandpoint, Colville, Kellogg, and Pullman. Thursday: There is decent model agreement that bands of snow will blossom just before sunrise across northeast Washington and far north Idaho and expand across the Spokane metro, the Silver Valley, and the Palouse in the 7-10AM time frame. Strong warm frontal lift combined with cold air aloft will contribute to the potential for moderate to heavy snow rates for a few hours in the morning. For some early commuters, the most significant snow may fall after they arrive at work, but for those out the door closer to mid morning, a winter-driving experience may await them. *Lowland Snow Amounts: At this time, 1-3 inches for Spokane, Pullman, Moscow, and Colville looks like a good bet in the morning. Amounts up to 4 inches will be possible around Coeur d`Alene, Deer Park, Sandpoint, Priest Lake, and the Silver Valley. Precipitation intensities should diminish by early afternoon as temperatures climb above freezing and accumulation efficiency in the lowlands decreases significantly. *Mountain Snow Amounts: The Cascades and the mountains of the Idaho Panhandle (especially along and south of I-90) will receive moderate to heavy snow Thursday, Thursday night, and Friday. Stevens Pass will likely get 2 to 3 feet of new snow on top of what they have gotten earlier this week. Lookout Pass on I-90 will have a good shot of 12 to 18 inches occurring Thursday and Thursday night. Folks with plans to recreate in the mountains or plan to go over the passes should check Avalanche conditions through the Northwest Avalanche Center or the Idaho Panhandle Avalanche Center as we continue to add another layer of heavy snow on top of what we have received in recent days. *Wind: Mild south or southwest winds will increase Thursday afternoon as a warm front surges into northeast Washington and far north Idaho. Forecasting the magnitude of warm front winds is tough because winds aloft don`t always translate to the surface. At this time, it looks like may be a strong enough pressure gradient across the Cascades to produce gusts of 40 mph or more in the Wenatchee area and Waterville Plateau Thursday afternoon. Elsewhere, gusts to 35 mph seem likely for the Palouse, West Plains and Moses Lake area. Afternoon pop up showers could generate a few higher gusts in eastern Washington, but showers shouldn`t be widespread. Friday: Overnight Thursday into Friday could be windier than Thursday afternoon. A clipper moving down the spine of the Canadian Rockies Friday morning has the potential to increase our surface gradient and winds aloft. If those winds surface overnight, we may see some gusts in the 40 to 50 mph range. The models don`t have much of a nocturnal inversion Friday night so this is a possibility, but forecasting overnight winds can be very tough. Shallow inversions can keep winds just above the ground. Friday afternoon could be another graupel/snow shower day. Afternoon warming combined with cold temperatures aloft (-35 to -38C at 500mb) will promote showers similar to what we experienced yesterday (Tue). /GKoch Saturday: Lingering mountain snowfall and possible morning fog/stratus. Light to moderate snow in the morning will dwindle down throughout the day. Northerly flow is expected to funnel down the Okanogan valley causing somewhat breezy winds into the Columbia Basin. Winds are expected to calm Saturday evening. Relatively clear skies for much of the region, especially Saturday PM. For the rest of the period, the forecast uncertainty is larger than usual. This is due to a split flow pattern aloft which has resulted in several different model solutions. Additionally, for the rest of the period, every morning currently holds the potential of fog/low stratus development. Sunday: Cascade crest snow is almost certain to occur at some point Sunday, maybe beginning as early as Saturday evening. A few model solutions suggest snow for the northern mountains and/or Idaho Panhandle, as well. Lowland precipitation is currently an uncommon solution for Sunday, but it cannot be ruled out. Monday: Could be quite impactful or not at all. At least light mountain precipitation is currently expected, with the Cascades being the most likely area to receive precip. On the other hand, it is a possibility that most of the forecast area receives precipitation Monday; it is more likely for Monday than it is for Sunday. If this happens and falls in the morning while temperatures are near or below freezing, the Monday morning commute may be impacted. Otherwise, Monday may be breezy. Tuesday: Morning looks like it will be mostly precip-free. Most precip, if any, will likely be light mountain snow, which could potentially pick up in intensity Tuesday PM. RC && .AVIATION... 18Z TAFS: A bank of low clouds between Spokane and Pullman should erode this afternoon as the late February sunshine does its work lifting the stratus into a cumulus deck. Look for increasing clouds overnight with rapid precipitation development across northeast Washington and north Idaho between 12-15z. Snow accumulations of 1 to 3 inches are expected between 15z-20z at KGEG, KSFF, KCOE, KPUW, and KSZT before air temperatures climb above freezing. Low ceilings will also accompany the arrival of the snow as well as a brief period of low level wind shear in the morning for KGEG, KSFF, KCOE, and KEAT. /GKoch && .PRELIMINARY POINT TEMPS/POPS... Spokane 27 40 31 41 25 40 / 0 100 40 20 10 10 Coeur d`Alene 26 40 30 40 22 38 / 0 100 60 40 10 10 Pullman 26 39 30 37 25 36 / 0 90 90 60 30 20 Lewiston 26 45 35 44 30 43 / 0 70 70 60 40 30 Colville 27 42 27 42 21 40 / 20 80 20 10 0 0 Sandpoint 25 37 30 38 23 36 / 10 100 70 40 20 10 Kellogg 22 36 29 35 23 35 / 0 100 100 80 40 20 Moses Lake 32 50 34 49 29 49 / 10 30 10 0 0 0 Wenatchee 30 46 32 43 29 44 / 20 30 20 20 20 10 Omak 28 45 30 45 26 43 / 20 30 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory from 7 AM to 1 PM PST Thursday for Coeur d`Alene Area-Idaho Palouse. Winter Weather Advisory from 4 AM to 1 PM PST Thursday for Northern Panhandle. Winter Weather Advisory from 7 AM Thursday to 4 PM PST Friday for Central Panhandle Mountains. WA...Winter Storm Watch from 10 PM PST this evening through Friday evening for East Slopes Northern Cascades. Winter Weather Advisory from 7 AM to 1 PM PST Thursday for Spokane Area-Washington Palouse. Winter Weather Advisory from 4 AM to 1 PM PST Thursday for Northeast Mountains. Wind Advisory from 1 PM to 8 PM PST Thursday for Waterville Plateau-Wenatchee Area. Winter Storm Watch from Thursday morning through Friday afternoon for Northeast Blue Mountains. && $$

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