676
FXUS66 KOTX 270003
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
403 PM PST Tue Nov 26 2024

.SYNOPSIS...
Seasonal temperatures continue through this week, with light
mountain precipitation expected, mainly over the Idaho Panhandle.
Travel impacts will be minimal this week. Areas of fog will
develop during the overnight and early morning hours each day
through the forecast period. The weather should turn drier for
most locations from late Saturday through Tuesday as a strong
ridge of high pressure builds over the region.

&&

.DISCUSSION...
Tuesday night through Thursday: Satellite imagery this afternoon
reveals a blanket of low clouds across much of eastern Washington
and north Idaho. The exception is for the immediate lee of the
Cascades where drier, westerly winds resulted in some clearing.
Locations under persistent cloud cover have seen very little
variation in the temperatures relative to their overnight lows
with places like Spokane, Pullman, and Coeur dAlene only warming
2 to 3 degrees today.

Outside of widespread low clouds and fog, generally quiet weather
is expected for the next couple days for the Inland Northwest. A
positively titled upper level trough spanning from northeast
California through western Montana is moving eastward as an upper
level ridge in the Gulf of Alaska shifts east. This will
transition the Inland Northwest into a broad northwest flow aloft
with subtle ridging influencing the region.

As the flow shifts to the northwest, moist upslope flow will
support mountain snow showers for the Cascades, northeast
Washington, and the Idaho Panhandle. Snow amounts will be light,
but light road accumulations in the late evening to the early
morning hours may result in slippery travel over Lookout Pass.

Light winds and a moist boundary layer will favor continued
stratus and fog across much of eastern Washington and north Idaho
Wednesday and Thursday. Visibility reductions down to a quarter of
a mile will be possible between Moses Lake and the Spokane area
early Wednesday morning. Those heading out early tomorrow morning
should allow for extra time to get to your destination safely.
/vmt

Friday to Tuesday: Model agreement during this period is very
good in terms of the weather pattern. On Friday and Saturday all
of the ensembles build a ridge over the Gulf of Alaska which
leaves the Inland NW in northwest flow. Embedded within this flow
will be a plume of atmospheric moisture (around 100-150% of the
seasonal normal) which will tease the northern third of WA and the
northern tip of the ID Panhandle. This will certainly result in
considerable cloudiness, as well as a chance of light
precipitation. The forcing for this precipitation will largely
result from weak mid-level warm air advection combined with weak
orographic ascent. Precipitation amounts will generally be a tenth
of an inch or less, with the heaviest amounts expected over the
mountains north of the Silver Valley in north Idaho. Snow levels
will likely be on the valley floors close to the Canadian border
into the Silver Valley. Places like Sandpoint, Bonners Ferry, and
Kellogg could conceivably see up to an inch of snow from Friday
into Saturday morning. Chances of seeing an inch are around 20% or
lower. For Lookout Pass we anticipate seeing snow amounts ranging
from 1-2.5 inches. Similar snowfall amounts are possible near the
Cascade Crest as well which would impact both Snoqualmie and
Stevens Passes.

From Saturday afternoon through Tuesday...the aforementioned upper
level ridge begins to head inland, resulting in drying and
warming conditions, at least above the ground. 850 mb temperatures
are expected to climb from -3 to 0C on Saturday afternoon to +4
to near 0C on Tuesday afternoon. While this warming will certainly
be realized in the mountains, we will likely see the formation of
strong inversions, with plentiful fog and stratus forming below.
Light winds and limited mixing could also result in a potential
air stagnation episode at least for several days. Our temperature
forecast shows highs in the mid 30s to lower 40s for highs with
lows in the 20s, however if we see the formation of widespread
stratus (likely), these highs are probably too warm and the lows
are too cool. By late Tuesday or Wednesday, a plume of significant
precipitable water (150-200% of the seasonal normal) will sag
south toward the international border and could reintroduce
small chances of precipitation into the forecast. fx


&&

.AVIATION...
00Z TAFS: Low stratus and fog continues to blanket much of the
Inland Northwest with widespread MVFR condtions being observed.
Models show stratus lowering and expanding back into MWH through
the night with widespread IFR and LIFR conditions through early
Wednesday morning. Breezier southwest surface winds across the
Blues into the Palouse may allow fog/mist to lift into a low
stratus deck around PUW after 15Z.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
High confidence for IFR/MVFR to continue and to expand back into
MWH tonight. HREF is showing a 70 to 90 percent for conditions at
GEG and MWH between 09-18Z.

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

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        31  36  28  38  26  34 /  10  20  10   0  10  10
Coeur d`Alene  32  36  29  37  26  34 /  30  30  20  10  10  20
Pullman        32  37  28  38  23  34 /  20  10  10  10   0  20
Lewiston       34  44  31  42  29  41 /   0   0   0   0   0  10
Colville       25  34  22  34  21  34 /   0  10   0  10  20  10
Sandpoint      29  34  27  34  25  33 /  30  50  40  30  30  40
Kellogg        32  35  30  36  25  33 /  50  70  60  40  10  40
Moses Lake     29  38  26  36  25  36 /   0   0   0   0   0   0
Wenatchee      29  40  27  36  26  39 /   0   0   0   0   0   0
Omak           26  36  25  36  25  36 /   0   0   0   0   0   0

&&

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

$$