Moscow, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

475
FXUS66 KOTX 302328
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
328 PM PST Mon Dec 30 2024

.SYNOPSIS...
Cooler temperatures are forecast this week with light lowland
snow expected on Wednesday. Another round of moderate to heavy
snow in the mountains on Friday with snow transitioning to rain
from south to north in the valleys.

&&

.DISCUSSION...
Tonight through Wednesday Night: A weak low over Vancouver Island
will slide southeast into Eastern WA and N Idaho tonight. There
isn`t much lift with this wave, but with a weak wave crossing the
Cascades into SE Washington tonight there is a chance of showers
mainly in the upslope favored areas of the palouse, southeast
Washington, Central Panhandle Mountains, and Camas Prairie.
Stevens Pass will continue to be favored for additional snow
showers where a Winter Weather Advisory still in place through 10
PM PST this evening. The other story tonight will be areas of fog
and freezing fog developing. The HREF shows this to be most
prevalent across the Upper Columbia Basin, West Plains, and then
extending west into the Moses Lake area and Waterville Plateau
Tuesday morning. On Tuesday a short wave ridge moves over the
region before the next system moves in Tuesday Night into
Wednesday. Temperature profiles are colder with this wave, but
precipitation amounts light with most areas picking up 1 inch or
less of snow. Timing of snow looks to reach Central WA close to
the start of the New Year, before tracking east into Eastern WA/ID
Panhandle late in the night into Wednesday morning. Wednesday
afternoon light snow shifts into the ID Panhandle with conditions
expected to dry out Wednesday evening and overnight although can
not rule out some light precipitation Wednesday Night due to weak
low level isentropic ascent and stratus over the region. JW

Thursday to Monday: The active pattern continues, with Friday the
wettest day of the period. A deep trough approaches the coast
Thursday. A weak impulse slides by the area during the day ahead
of it, but at the same time the warm front leading the offshore
system begins to lift into the area. Light precipitation chances
linger over the area in the morning and increase in the afternoon,
though overall the best risk will be around the Cascades and ID
Panhandle mountains. Any precipitation that falls will be mostly
in the form of snow, but a rain/snow mix will be possible over the
deeper Columbia Basin into the L-C Valley. Some moderate
accumulations are possible around Stevens Pass, with up to 5
inches, and lighter amounts of 1-3 are possible toward Lookout
Pass. Elsewhere snow amounts are expected to be less than an inch
and in most cases away from the mountains less than a half inch.

Thursday night the warm front continues to lift in, with a plume
of moisture coming north with it with PWATs around 150-200% of
normal. Precipitation chances will continue to rise through the
night, becoming more likely around the Cascades and deeper
Columbia Basin overnight. Then heading into Friday the occluding
front, with supporting upper trough on its heels, brings some the
best lift. This will combine with the moisture plume to bring a
good chance of precipitation throughout the region. The chances
remain high throughout the day, then the chances start to decrease
in the lee of the Cascades Friday night into Saturday morning.

Precipitation type will be somewhat tricky as is often the case
in this part of the country. Yet overall milder air coming into
the Columbia Basin will bring a rain/snow mix over the Moses Lake
area east to the Palouse and north toward the foothills of the
northern mountains, including the Spokane/CdA area. All rain is
more likely over the deeper Columbia Basin and L-C Valley and even
much of the Palouse and Moses Lake area by Friday afternoon. Snow
will be more likely around the Cascades to Waterville Plateau and
across the northern mountains and above about 3500-5000 feet
around the Central Panhandle. Just how persistent the cold air
holds on in these areas will influence how much snow falls in
these areas. Some rain will start to mix in to the Waterville
Plateau and Wenatchee Valley and perhaps even the Methow valley in
the afternoon. Right now the forecast shows about 5-10 inches in
the mountains and 1-3 inches over the Cascades valley and northern
mountain valleys. If anything accumulates around the upper
Columbia Basin, Spokane/CdA area and higher Palouse it generally
looks like less than a half inch. Rain amounts around 0.30 to 0.60
inches will be possible.

From Saturday through Monday the area transitions to a more west-
northwest flow. Precipitation chances remain the likely or higher
category across the Cascades and the eastern third of WA and ID
Saturday morning as the upper trough is still shifting through.
This will remain as mountain and western basin snow and a
rain/snow mix over the upper Columbia Basin to Spokane/CdA area
and Palouse, with rain toward the L-C Valley. Some light to
moderate accumulations are still possible around Stevens and
Lookout Pass. Then later Saturday and continuing into Sunday and
Monday the best chances for precipitation retreat to the mountain
zones, though the risk does not entirely end elsewhere, but the
risk is slight to moderate.

Temperatures are forecast to be near to slightly above normal,
with highs in the 30s and low 40s and some 20s in the sheltered
northern Cascade valleys. Lows will be in the 20s and 30s, with
some teens in the sheltered mountain valleys. /Solveig

&&

.AVIATION...
00Z TAFS: A moist boundary layer and low level upslope flow will
continue to promote IFR/MVFR stratus over NE Washington into the
ID Panhandle as well as the Okanogan Valley into Tuesday. Drier
conditions in Central WA will promote VFR conditions through much
of tonight. Overnight models are in good agreement that the
stratus will expand westward into the Columbia Basin with IFR
conditions spreading into Moses Lake near 12z. With light boundary
layer winds on Tuesday the stratus is likely to persist through
the day around the Moses Lake area up into NE Washington and the N
Idaho Panhandle.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence has
decreased somewhat with the evoluation of stratus tonight with
degree of development/expansion across the Columbia Basin and
around KGEG. This is due to larger temp/dew point spreads across
Central WA this afternoon, and also incoming cloud cover with a
mid level wave that could slow the stratus expansion. Yet the
HREF model gives a 50% chance of IFR conditions at MWH as early as
06z, increasing to 80% at 11z. The forecast leans towards the
later timing given the drier boundary layer to initially start the
tonight period in the Columbia Basin. Also some clearing of the
stratus around KGEG and some snow cover could allow patchy ground
fog to develop this evening allowing the incoming mid clouds leads
to lower confidence in fog impacting the TAF site this evening
with the overnight hours more likely for fog. At 12z Tue the HREF
has a 70% chance of CIGS below 250 feet at KGEG. 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        27  33  28  32  28  35 /  20   0  20  60  30  30
Coeur d`Alene  28  33  25  32  26  35 /  10   0  10  60  30  40
Pullman        29  36  27  33  27  35 /  20   0  30  70  50  50
Lewiston       32  41  32  39  32  42 /  10   0  30  40  30  30
Colville       28  32  24  32  23  33 /  10   0  40  60  30  40
Sandpoint      27  32  26  31  26  32 /  20  20  30  70  50  50
Kellogg        28  33  24  32  26  35 /  30  30  20  70  50  60
Moses Lake     27  35  29  34  29  37 /  10   0  50  50  30  20
Wenatchee      24  32  28  33  29  35 /  10   0  60  40  40  20
Omak           28  31  27  31  26  33 /  10   0  60  50  30  20

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory until 10 PM PST this evening for Western
     Chelan County.

&&

$$