Area Forecast Discussion Issued by NWS Spokane, WA
000
FXUS66 KOTX 282359
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
359 PM PST Tue Nov 28 2023
.SYNOPSIS...
Stagnant conditions with periods of freezing fog and low clouds
will continue through early Thursday. A significant pattern
change at the end of the week will lead to several rounds of snow
for most of the Inland Northwest with the potential for heavy snow
near the Cascades. Much warmer weather will develop early next
week with the wet weather continuing.
&&
.DISCUSSION...
Through Wednesday night:
Generally light winds and stagnant conditions will enable nuisance
freezing fog and areas of low clouds to continue through Wednesday
night. The low stratus deck, in particular, has maintained its
stranglehold across much the Columbia Basin and Cascade-adjacent
valleys, occasionally drifting into the Palouse and Lewiston areas
as well. The areas of freezing fog are likely to expand overnight
tonight. In addition, the Air Stagnation Advisory remains in
effect until late Thursday morning. Daytime temps to run about 5
degrees below normal on Wednesday.
...Much wetter and snowier pattern expected to kick off December...
Thursday through Tuesday: Ensembles continue to have the ridge
flatten and shift East as a trough begins to dig south along the
coast. The Pacific Northwest will impacted by a moisture plume being
pushed into the region by a Gulf of Alaska Low and a high pressure
off the California Coast. Ensembles are bringing a series of
shortwaves through the region starting late Thursday and lasting
into next week. The Inland Northwest can expect several rounds of
precip into to the start of next week. Ensembles are steadily
increasing the amount of precip associated with these waves.
The first wave late Thursday into Saturday will bring widespread
snow to the region with the heaviest snow amounts in the Cascades.
The Cascades mountain passes could see 10 to 15 inches. The amounts
across the Basin are 1 to 3 inches. Northern Valleys are expecting
around 2 to 4 inches. The Idaho Panhandle could get 1 to 4 inches.
Lookout Pass is expected to receive 4 to 8 inches. Morning commutes
should expect snowy conditions.
The second wave will be Sunday into Tuesday. Temperatures will be
a warming trend with the Southerly flow pattern. It will change
the precip type across the Basin to rain or a rain/snow mix.
Portions of the northern Basin could see an additional inch.
Cascades will again receive the brunt of the moisture. Pass could
receive another 12 to 18 inches. The northern valleys and Idaho
Panhandle should see an additional 1 to 3 inches. Lookout Pass
could see another 6 to 8 inches. By Tuesday, the warmer surface
temperatures will keep the Basin and valleys in a rain precip type
with snow for the mountains. Snow levels are expected to climb
above 4000ft. Highs for the period will be in the 30s. Highs will
then climb into the 30s and low 40s by Monday. Lows will be in the
upper teens and 20s through Sunday. Lows will then climb into the
30s for the start of the week. /JDC
&&
.AVIATION...
00Z TAFs: IFR/LIFR cloud stratus layer extending from Moses Lake
to Pullman southward into the Lower Columbia Basin is expected to
expand north and east tonight as boundary layer winds are light
out of the south and southwest. None of the models are handling
the north and east extent of this cloud deck currently so forecast
based mainly off satellite trends and expected trend of the
stratus to the north and east overnight. Pullman has already gone
down to a 1/4SM, with the fog, and expected to reach KGEG around
03-04z, and KSFF near 06z. There is lower confidence for KCOE as
the progress may slow with northeast winds still in this area.
KEAT carries lower confidence as well, as the stratus slowly
expand from Ephrata and Moses Lake toward the west. Once the
stratus moves in, it is likely to hang around through the day
Wednesday due to light boundary layer winds although some gradual
lifting of the stratus layer is expected.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS: Low confidence how
long KPUW will stay at 1/4SM. With models showing not much of an
east wind overnight and the low level cold pool quite strong,
forecast keeps at 1/4SM with some indication of a light west-
northwest boundary layer wind keeping the fog in place. Low
confidence for timing when the low cloud deck moves into Lewiston.
High confidence the fog bank will move into GEG this evening, with
moderate confidence of visibility down to 1/4SM. JW
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 19 31 19 33 24 35 / 0 0 0 10 60 80
Coeur d`Alene 21 34 20 34 26 34 / 0 0 0 10 70 80
Pullman 21 36 20 33 26 36 / 0 0 0 10 80 80
Lewiston 26 37 25 36 31 43 / 0 0 0 10 60 60
Colville 15 34 14 34 18 32 / 0 0 0 10 50 80
Sandpoint 20 34 20 35 23 31 / 0 0 0 10 70 90
Kellogg 27 38 24 34 30 34 / 0 0 0 10 80 90
Moses Lake 18 31 18 34 21 39 / 0 0 0 10 30 50
Wenatchee 26 36 25 32 25 36 / 0 0 0 10 30 60
Omak 22 36 22 34 24 36 / 0 0 0 10 20 50
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 11 AM PST Thursday for Central
Panhandle Mountains-Coeur d`Alene Area-Northern Panhandle.
WA...Air Stagnation Advisory until 11 AM PST Thursday for Central
Chelan County-Moses Lake Area-Northeast Mountains-Okanogan
Highlands-Okanogan Valley-Spokane Area-Upper Columbia Basin-
Waterville Plateau-Wenatchee Area-Western Chelan County-
Western Okanogan County.
&&
$$