Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 211153
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
453 AM PDT Thu Mar 21 2024

.SYNOPSIS...
Expect cooler and wetter weather over the next several days. Any
snow will be confined to the higher mountains through Friday, but
snow levels will drop over the weekend into early next week
leading to the potential for lowland snow in north Idaho. An
active weather pattern will continue through next week with a
series of storms bringing mountain snow, and mainly rain in the
valleys except some snow at times overnight for the northern
valleys.

&&

.DISCUSSION...

...MUCH COOLER TEMPERATURES AND LOWERING SNOW LEVELS WITH LIGHT SNOW
POSSIBLE IN NORTHERN VALLEYS OVER THE WEEKEND...

Today and Thursday night: Expect locally gusty westerly winds
today, particularly across northern ID, southeast WA, and the
Waterville Plateau. Enough moisture is in place for chances of
showers through Thursday night as well, though it will mostly be
confined to N ID, extreme eastern WA, and areas adjacent to the
Cascades. Warmer than normal temperatures will continue today as
well, but still cooler than we`ve been experiencing over the last
several days. The more dramatic pattern shift will then develop
later. /KD

Friday night through Sunday: The weekend will welcome a dramatic
change in the weather to cooler and wetter conditions. A cold upper
level trough of lower pressure will push inland off of the eastern
Pacific during this time and replace the warm, dry ridge that we had
in place since late last week. Precipitation type will vary across
the region and is the most challenging part of the forecast. The
general consensus is for a surface low to spin up in the lee of the
Cascades Friday night around Yakima and then generally track
northward toward Wenatchee into the western portion of the Columbia
Basin by Saturday morning. A deformation band will form out ahead
of this surface feature with moisture wrapping around across the
Idaho Panhandle and up across eastern Washington. This deformation
band looks to get hung up across the northern zones before the
low then shifts east across the basin into the Idaho Panhandle
through Saturday night into Sunday morning with wrap around
moisture following the low as it does so. Where the deformation
band ultimately sets up will play a big role as to where the
heaviest precipitation will fall, which will be on the order of
0.5 to 1.0 inches. The generally consensus from the ensembles is
that will take place across the northern half of the forecast
area.

Colder air will funnel south out of Canada, especially so down
through the Purcell Trench in the Northern Panhandle. Snow levels
will drop through Saturday and should begin to see precipitation
transitioning over to snow around Bonners Ferry sometime from
Saturday morning into Saturday afternoon. Timing isn`t great to see
snow accumulating on roads with a daytime arrival of this band. The
impacts for the valleys will be more likely Saturday night into
Sunday morning. Colder air continuing to infiltrate the region from
the north will result in a further lowering of snow levels with a
transition to snow in the valleys generally north and along the
Highway 2 corridor. How much snow will actually accumulate on roads
is a big question mark, especially the further south we go as road
temperatures will be starting out quite warm. Where the heaviest
precipitation under the deformation band will also play a role. In
general, the best potential for snow to accumulate and have travel
impacts will be in the northeast corner of the forecast area from
the Pend Oreille River Valley over into the Northern Panhandle. The
mountain passes will also likely see roads becoming snow covered:
Stevens Pass, Loup Loup Pass, Sherman Pass, 4th of July Pass, and
Lookout Pass being the top contenders. Below is some probabilistic
snow accumulations over the weekend off of the National Blend of
Models (NBM):

*Chances of at least 1" of snow: Sandpoint = 66%, Colville = 20%,
 Spokane = 18%, Coeur d`Alene = 36%

*Chances of at least 2" of snow: Sandpoint = 53%, Colville = 13%,
 Spokane = 7%, Coeur d`Alene = 18%

*Chances of at least 4" of snow: Sandpoint = 26%, Colville = 2%,
 Coeur d`Alene = 2%

*Chance of at least 6" of snow: Sandpoint = 10%

*Chances of at least 8" of snow: Stevens Pass = 18%, Sherman Pass
 = 10%, Lookout Pass = 50%

Temperatures will cool to below normal. The forecast was generally
adjusted to be a bit colder than the NBM for Saturday based on the
fact the precipitation under the deformation band will make it
difficult warm up in the afternoon, especially the northern half of
the forecast area. Valleys in the Northeast Mountains to the
Northern Panhandle will have a difficult time warming above 40
degrees.

Sunday night through Thursday: The weather pattern looks to remain
progressive and active with snow levels generally hovering between
2500-4000 feet. Multiple shortwave disturbances will push across
with the next arriving on Monday, another around Wednesday, and
then one toward the end of the week. There is the potential for
wet snow in the northern valleys next week, primarily during the
colder overnight hours when snow levels will more likely be down
around that 2500 foot mark. Expect winter travel conditions over
the mountain passes. Wester flow with a more zonal flow pattern
will favor heavier snow over the Cascade passes and for Lookout
Pass in the Idaho Panhandle. Temperatures will remain below
average for mid to late March. Gone are the days of 70 degree
temperatures...for now...no worries though, as we are still in
March and the warmer weather will soon return at some point. /SVH

&&

.AVIATION...
12Z TAFS: Chances for light rain will continue today, with the
best chances at the KCOE and KPUW terminals. Occasionally breezy
southwest/west surface winds are also anticipated today.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence of
VFR conditions across most of the Inland NW through 12Z Fri. /KD

------------------------

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        57  39  59  40  46  34 /  20  10  40  70  80  70
Coeur d`Alene  54  38  56  39  44  32 /  40  20  50  70  90  80
Pullman        54  39  60  40  49  36 /  20  10  40  70  80  70
Lewiston       63  43  66  45  54  39 /  10  10  20  50  80  70
Colville       58  35  55  36  43  33 /  60  10  50  70  80  80
Sandpoint      50  37  46  35  38  29 /  50  30  70  80  90  80
Kellogg        50  41  54  41  44  33 /  60  30  60  80  90  80
Moses Lake     65  40  63  42  56  37 /   0   0  20  60  70  40
Wenatchee      62  43  58  42  50  37 /   0  10  20  60  70  40
Omak           63  40  59  42  49  36 /   0  10  30  60  80  60

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&

$$


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