585
FXUS66 KOTX 062255
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
255 PM PST Mon Jan 6 2025

.SYNOPSIS...
High pressure will build over the Inland Northwest Monday and
Tuesday with areas of low clouds and fog. A pair of disturbances
will deliver chances for snow mainly to the mountains Wednesday
and again Friday.

&&

.DISCUSSION...

Today through Wednesday: The biggest forecast challenge through
Wednesday is the evolution of the low stratus/fog and temperatures
under the influence high pressure. The morning HREF ensemble
advertises stratus/fog deck building towards the northwest overnight
into Tuesday. Subsidence and very wet soils will promote the
formation of fog, especially in areas that can scrub out a little
more cloud cover in the next couple hours (highway 2 corridor from
Spokane to the Waterville Plateau). Along with weak boundary layer
winds and potential for radiational cooling, the stage appears set
for widespread dense fog. The diurnal spread for temperatures on the
National Blend is aggressive cold with temperatures at night
which does not make sense with the stratus deck. The infamously
cold Methow Valley will likely see temperatures dip into the
single digits and teens tonight before the stratus deck
establishes itself there. Some moisture from systems over the
Pacific deliver some small chances for snow showers overnight
Tuesday into Wednesday near the Cascade crest and in north Idaho.
Snow amounts will be generally around 0.1". db

Thursday to Monday: A relatively benign weather pattern is
interrupted by a system around the end of the work week. A ridge
of high pressure will keep things dry Thursday. An easterly flow
will push the deeper low clouds toward the lee of the Cascades and
central WA, while eastern areas see partly to mostly cloudy skies
especially in the afternoon. Some light drizzle/freezing drizzle
could be squeezed out of the stratus toward the Cascades/western
basin.

Then Thursday night into early Friday morning a warm front lifts
into the area, while a cold front and upper trough pushes by
through during the day Friday. Thursday night clouds thicken, with
a chance of snow coming into the Cascades, while other areas see
patchy fog and maybe some flurries. Friday the chance of snow
comes to a larger portion of the areas. A rain/snow mix changing
to rain comes into the deeper basin, lower Palouse and L-C Valley;
some of the rain/snow mix comes into the Columbia Basin/Spokane/C`dA
Area and higher Palouse in the afternoon to evening. The precip
then begins to decrease later Friday afternoon into Friday night,
with the highest chances remaining near the Cascade crest and over
the Central Panhandle to Palouse southward through the evening.
Overnight the chances largely retreat to the Idaho Panhandle and
higher Palouse southward and to the immediate Cascade crest.

* Snow amounts: Light to moderate snows are forecast for the
  mountains, including the Cascade crest and central Panhandle
  mountains with around 3-7 inches near Stevens Pass and 2-5
  inches near Lookout Pass. The sheltered northeast valleys,
  higher Palouse, Camas Prairie and Blues could see 1-2 inches of
  snow. The remainder or the eastern third of Washington, the
  northern mountains and sheltered Cascades valleys right now are
  projected to see less than 1 inch, if even a half inch. This
  will be monitored for adjustments, should models trend wetter
  and/or colder which could lead to a bit more snow. Models
  currently show only a 30-40% chance of 1 inch or greater in
  Spokane and about a 50% chance toward Coeur dAlene. The deeper
  basin and L-C Valley are not expected to see much snow at all.

The system also comes with some breezy conditions. On average in
the unsheltered areas, winds of 10-15 mph are forecast with gusts
to 20 to 25 mph. Locally higher winds are forecast near the Blue
Mountains and downwind into the Palouse and near the Waterville
Plateau. Speeds of 15-25 mph will be possible, with gusts 30 to
40 mph. The higher speeds are projected to be near the Blues
Mountains.

From Saturday to Monday the area transitions to a northerly flow,
with impulses dropping down from the BC. Precise timing and track
of those impulses is not solid agreement yet, but look for
continued snow shower chances around the mountains zones and
occasionally around the Palouse. However we will have to keep an
eye on the potential for some broader snow shower chances, if the
impulses and instability sync up to bring some convective snow
showers between Saturday night and Sunday night over the remainder
of the eastern third of WA and lower ID. Such a set-up could
bring brief heavier bursts of snow. Confidence is low and
ensembles show the potential for measurable snow at less than 15%
in these locations. These, however, are the tricky kind of
impulses that could drop a quick inch or so of snow in one spot,
but not accumulate at all 10 miles away. Otherwise look for patchy
fog and partly to mostly skies. Temperatures will be near normal
into Saturday, then drop every so slightly below normal into early
next week. /Solveig

&&

.AVIATION...
18Z TAFS: IFR/MVFR stratus will continue through much of the day
for PUW-LWS-EAT. MWH remains on the edge of the stratus deck but
satellite indicates northwest movement of the stratus keeping IFR
conditions present. KGEG-KSFF-KCOE have seen improvements over the
last couple hours as some stratus is scoured out by northeast
winds. KCOE-KSFF have the best chance to be VFR as this occurs.
KGEG has the lowest confidence of clearing out. Rain soaked soils
will promote the northward expansion of fog from the Palouse
toward Spokane as well as the development of radiation fog in
valleys of north Idaho and northeast/north central Washington that
clear out this afternoon.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
for VFR conditions for KCOE until this evening, IFR-MVFR for PUW-
LWS. Lower confidence in the evolution of the stratus for KSFF-
KGEG-KEAT this morning and afternoon.


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

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        29  33  29  35  25  35 /   0   0   0   0   0   0
Coeur d`Alene  27  33  27  35  23  36 /   0   0   0  10   0   0
Pullman        30  35  29  37  25  36 /   0   0   0  10   0   0
Lewiston       33  40  32  42  29  40 /   0   0   0   0   0   0
Colville       24  31  26  34  21  33 /   0   0  20  10   0   0
Sandpoint      25  34  27  35  23  33 /   0   0  20  30   0   0
Kellogg        25  34  27  35  23  36 /   0   0   0  30   0   0
Moses Lake     30  35  30  36  27  37 /   0   0   0   0   0   0
Wenatchee      30  34  30  36  29  35 /   0   0   0   0   0   0
Omak           27  32  28  34  24  34 /   0   0   0   0   0   0

&&

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

$$