Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 240024

Area Forecast Discussion
National Weather Service Spokane WA
424 PM PST Mon Jan 23 2017

Another weak system will move through the region tonight through
Wednesday and will result in light snow showers or snow flurries.
By midweek a strong ridge will build over the Pacific Northwest.
This will bring dry and cooler weather with an abundance of low
clouds and fog in the valleys.


Tonight through Wednesday...In the big picture, satellite imagery
shows the closed low dropping south along the OR/CAL coast. The
moisture that was wrapping around the low is sagging south as
well. Meanwhile high pressure is nosing into B.C. this afternoon
with a couple of weak short wave disturbances expected to drop
south through the Inland Northwest tonight through Wednesday. Some
mid and upper level moisture is associated with these waves and
with up-sloping into the Panhandle mountains, the Blues and the
Camas Prairie there will be the chance of light snow showers.
Accumulations from tonight through Wednesday afternoon will be
light with the possibility of around a half inch for the
Pullman/Moscow area and maybe 2-3 inches for the St Joe mountains.
The main challenge for the next 2 days will be widespread stratus
and to a lesser extent fog across the region. Some mixing/clearing
will be possible each afternoon, but that will be short lived and
the stratus is expected to reform soon after sunset. Some light
Snow flurries will be possible for extreme eastern Washington and
the Panhandle as these waves move through the region. Model
guidance shows 850 temperatures cooling a few degrees both Tuesday
and Wednesday and with out much mixing to speak of expected
temperatures to cool into the upper 20s and lower 30s which is 4-6
degrees below average. Tobin

Wednesday night through Monday: Ridge of high pressure will build
in and strengthen over the region at the end of the work week.
Before the ridge takes a stranglehold over the region though,
there will be some weak upper level energy that will ride south
across the region on the front side of the ridge. Snow showers
will continue to be possible with this energy over the
southeastern portions of the region Wednesday night through
Thursday, and mainly for the Central Panhandle Mtns, Idaho Palouse
to Northeast Blue Mtns and into the Clearwaters.

The ridge axis will then shift on top of the region Thursday
night. Strong subsidence will ensue and temperatures aloft will
warm, which will strengthen low level inversions region wide.
Lots of fog and/or low stratus cover is expected. The low clouds
will keep diurnal variations in temperature at minimum with many
areas remaining in the 20s to low 30s. Mountain tops will see the
best potential for sunshine and will generally see warmer daytime
temperatures than the valleys that will be stuck under the low
clouds. The southeastern portion of the region may see enough
mixing to clear out the low clouds Friday into the weekend;
however, it looks as if the boundary layer moisture will be deeper
across the northern valleys, western basin and into the east
slopes of the northern Cascades where fog and stratus will have a
much harder time breaking up.

There will be a weak shortwave disturbance that rides up over the
ridge on Sunday. Miner snow chances will be possible over the
mountains of the Cascades, to northeast WA and in the ID
Panhandle. Just enough mixing may break up the low clouds a bit
more with this wave. Air Stagnation will become more of a concern
over the weekend with the potential for stronger inversions. The
shortwave on Sunday may be enough that we will not need to issue
an Air Stagnation Advisory, but the ridge will rebound into early
next week with stagnant conditions likely returning. /SVH


00Z TAFS: Fog and stratus will be the main forecast challenge for
the next couple of days. The fog for most of the TAF sites has
lifted into a stratus deck this afternoon. The exception is
KPUW/KLWS where the winds shifted to light southwest-west and fog
slammed back into those sites...the winds are expected to remain
light out of the west and will keep the fog in place. KLWS may
see the fog dissipate for a brief time early this evening...but it
will be brief. Some light flurries will be possible out of the
stratus deck for KPUW-KLWS as well. Otherwise it will be mainly
stratus for KCOE-KSFF-KGEG-KMWH as the boundary layer moisture
sloshes around the the terrain. A series of weak disturbances will
track south along the ID/MT border through Wednesday and may
result in isolated to scattered snow showers for the eastern TAF
sites. KEAT looks to be in the best shape with mainly VFR
conditions. Tobin


Spokane        25  31  21  30  23  29 /  20  20  10  10  10  10
Coeur d`Alene  25  31  21  31  23  30 /  20  40  20  20  20  10
Pullman        24  32  21  31  25  30 /  20  40  20  20  20  20
Lewiston       27  35  25  34  27  33 /  20  20  10  10  20  20
Colville       27  30  20  30  21  28 /  10  10  10  10  10  10
Sandpoint      27  31  22  30  23  30 /  10  30  20  20  20  10
Kellogg        26  30  20  29  23  29 /  20  40  30  30  40  20
Moses Lake     25  32  18  30  23  30 /   0  10  10  10  10  10
Wenatchee      25  30  20  28  25  27 /   0   0   0  10  10  10
Omak           26  29  18  29  24  28 /  10   0  10  10  10  10



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