Spokane Valley, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

157
FXUS66 KOTX 211207
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
407 AM PST Thu Nov 21 2024

.SYNOPSIS...
Thursday will be cloudy with periods of rain and mountain snow.
Friday will be quite wet with the arrival of a strong warm front
causing snow levels to rise above most mountain passes by Friday
afternoon. The weekend into early next week will feature
seasonably cool temperatures and chances for valley rain and snow
and periods of mountain snow.

&&

.DISCUSSION...

Today and tonight: A diffuse frontal boundary is draped from
southwest to northeast over the Inland NW keeping an axis of
moisture draped overhead. Weaker waves ejecting from the offshore
low are tracking along the boundary resulting in periods of light
to locally precipitation. One such wave is making its way through
Eastern WA and N ID this morning, a second will arrive this
afternoon and early evening. There is good agreement that the most
concentration precipitation will remain over N ID and the eastern
third of WA mainly east of a line from Colville to Moses Lake
though, given the high moisture content of the air mass...hard to
fully remove precipitation all together from the forecast area.
Cooler air remains trapped in our northern valleys with wet snow
still falling at locations like Bonners Ferry, Priest Lake,
Colville, and Republic. Snow levels via the 00z balloon data was
around 4400 feet MSL however closer examination of model soundings
indicate these northern valleys are dealing with a near
isothermal profile around 32-33F. This will result in a mix of
light rain or wet snow with snow more likely when precipitation
rates increase. Given what we are seeing on cams at this hour,
will allow the snow advisories to play out through the morning
hours. The break between waves today will allow the snow levels to
creep northward and the next round of precip should result in a
lower probability for snow to make it to valley floors for these
northern valleys but continue in the mountains. Otherwise it will
be a soggy, grey day across the Inland NW with periods of light
rain or drizzle, light winds, and temperatures in the upper 30s to
40s.

Friday: A second low will rapidly deepen off the WA Coast while pivoting
northward toward Vancouver Island. This will lift a warm front
into the region and briefly usher the atmospheric river currently
aimed at N Cali into the Inland NW. PWATS increase on the order of
200-210% of normal with widespread light to moderate
precipitation expected. There is a 50-80% chance for at least
0.50" of liquid with areas of the Blue Mountains and Idaho
Panhandle forecast to be closer to an inch or more (50-70%
chance). Needless to say, a soaker is on its way. Snow levels will
rise near 6000 feet or higher for the entire event for much of SE
WA and the lower ID Panhandle. For NE WA and N ID, these levels
will briefly nose close to the Canadian border for a shorter
period Friday. Snow levels will be much more of a challenge for
Central WA and in particular, the Cascades where some cold air
damming is expected. Thinking the rain/snow line will reach
Stevens Pass around 4500 feet but be slower to arrive in the North
Cascades and Methow Valley. These areas come with low confidence
with models indicating a 3000 foot layer of air to dance around
the 0C isotherm. Valleys for the most part should be rain or wet,
non accumulating snow but did delay the transition at locations
like Mazama and Winthrop which could receive several inches of wet
snow. Stevens and Sherman Passes will have the potential for 2-5
inches of snow before becoming too warm. Breezy east to southeast
winds will return to the region before shifting to the
south/southwest as the warm front lifts through. Temperatures will
be mild with highs in the 40s and 50s. Some ponding of water in
fields and urban areas with poor drainage is expected. Streams and
creeks will experience increased flows as well...likely more into
Friday night and Saturday but there is low confidence for
flooding. This will also bring the potential for increased flows
on the Palouse, St Joe, and Coeur D Alene rivers with the latest
forecast indicating a 2-3 foot rise but remaining well below bank
full.

Friday night through Saturday: A cold front will press into the
region bringing lower snow levels and end to the feed of
subtropical moisture and high snow levels. Light to moderate
precipitation will continue to develop along the frontal boundary
as it tracks through eastern WA and North Idaho. Snow levels will
lower enough such that rain will transition back to snow for
Lookout Pass with return to winter travel conditions. The Cascade
passes will also be contending with a return to snow showers and
potential for winter driving conditions. The cooler air mass will
be of a maritime nature which will only bring snow levels down
toward 3000. Much of Central WA will dry out and slowly work into
eastern WA. A shift to more west/northwesterly flow aloft will
favor the Idaho Panhandle for scattered showers. Saturday morning
should start off mild with temperatures above freezing; high
temperatures warm in the 40s Saturday afternoon then cool near or
below freezing Saturday night. /sb

Sunday through Thursday: Light mountain snow showers will stick
around through much of next week. High temperatures next week will
be in the 30s and 40s and low temperatures in the 20s to 30s. Snow
levels from the experimental Utah Snow Ensemble show the wet bulb
0.5C level well below both Stevens Pass and Lookout pass the whole
time. Models show the upper low still present off the Washington
coast sending a vort max into the region Sunday morning. With snow
levels around 1000-2500 feet along and north of US-2, a round of
light snow up to an inch is expected. The NBM probabilities of a
dusting of snow are 20-50% in the lowlands and a 50-60% chance of
an inch or more at Stevens and Lookout pass Sunday. 80% of the
ensemble clusters leave the inland NW in cool and showery
northwest flow after the low moves inland Tuesday. /DB

&&

.AVIATION...
12Z TAFS: Widespread IFR to MVFR conditions are expected through
the day Thursday aside from at the Lewiston Airport (LWS) where
VFR conditions are expected to prevail. Another round of
precipitation will move into the region later this morning
bringing light rain.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Confidence is high for the area to remain under a stratus deck
with MVFR conditions at KGEG-KSFF-KCOE. Low confidence on ceiling
heights or dense fog development with probability of less than
half a mile below 20% around KEAT and KMWH.
-----------------------

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        44  37  48  37  43  31 /  60  60 100  80  50  20
Coeur d`Alene  44  37  47  36  42  31 /  70  60 100  90  60  40
Pullman        45  39  49  36  42  31 /  70  80 100  90  60  30
Lewiston       51  43  55  40  48  35 /  40  70  90  80  50  20
Colville       40  32  42  32  41  25 /  50  60 100  80  50  30
Sandpoint      39  34  42  34  39  30 /  90  80 100 100  80  60
Kellogg        43  38  46  36  39  34 /  90  70 100 100  90  60
Moses Lake     46  38  49  36  45  30 /  50  90 100  40  30  10
Wenatchee      38  36  42  32  42  30 /  60  80  90  20  20  10
Omak           38  34  42  33  43  28 /  40  70 100  70  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory until 10 AM PST this morning for Central
     Panhandle Mountains-Northern Panhandle.

WA...Winter Weather Advisory until 10 AM PST this morning for
     Northeast Mountains.

     Winter Storm Warning until 5 AM PST early this morning for
     Okanogan Highlands.

&&

$$