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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.


&&

$$