Lewiston, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

934
FXUS66 KOTX 150556
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
956 PM PST Thu Nov 14 2024

.SYNOPSIS...
Drier conditions return Friday and Saturday with areas of morning
fog. Heavy mountain will return Saturday night and Sunday with
another weather system moving through the area. There is a chance
of some light lowland snow Sunday morning. Next week looks much
drier with high pressure settling in.

&&

.DISCUSSION...
Tonight through Friday: The period will be brief break sandwiched
between an exiting system and another expected on Saturday.
Lingering showers will continue to bring light snow to the higher
terrains but little to no accumulation expected. With the
abundance of moisture in the boundary layer patchy fog during the
early morning is expected. It is expected to impact morning
commutes. OVernight lows will be in the upper 20s to low 30s.
Friday highs will be in the 40s to low 50s. /JDC

Saturday through Monday: A Winter Storm Watch has been issued for
Saturday through Monday for heavy mountain snow over the Cascade
Passes. Weak ridging will start the day Saturday, before a deep
trough slides into the region with the next round of mountain snow
and lower elevation rain/snow. Saturday will start out dry with
temperatures warming to near 40 before precipitation spreads east
throughout the day. With this system, snow levels will drop to 1500-
2500 feet overnight. Lower elevations mainly north of Highway 2 and
down through the Palouse could see their first snow of the year,
although only light accumulations are expected. Lower elevations
snow will accumulate on grassy surfaces as roadways will likely be
too warm. The forecasted amounts have not changed much since
yesterdays forecast, with Central WA seeing 0.10 to 0.25 inches of
rain, while Eastern WA and ID Panhandle will see 0.5 to 1.0 inch.
Mountain Passes and the higher elevations could see upwards of 2.0
inches of liquid. With snow ratios expected to be 10 to 15 inches of
snow to one inch of liquid, the mountain passes are forecasted to
see some of the highest snow totals of the year so far. Models are
hinting at a convergence zone setting up over Stevens Pass Sunday,
with winds up to 40 mph possible. Snowfall will make travel
challenging through the Cascades and Lookout Pass.

Chance of snow :   6    12   24   36  Sat PM-Mon PM:
-----------------------------------------------
Stevens Pass   :  100%   100%  45%   15%
Washington Pass:  100%   100%  50%    5%
Sherman Pass   :   50%     5%   0%    0%
Lookout Pass   :  100%    80%  10%    0%

With the snow elevation hovering around 1500 to 2000 feet Saturday
night, higher elevations around Spokane/CDA and areas to the west of
Spokane have the best chance of seeing snow. Most areas will see an
inch or less, but cannot rule out localized amounts to 2 inches.
Snow will quickly turn to rain as warming begins to move into the
area.

Winds will also increase on Sunday afternoon in the Columbia Basin
and Palouse area, with southerly gusts up to 35 mph, decreasing
slightly Sunday night. Winds will continue to be breezy with gusts
to 20 mph Monday. /KM

Tuesday through Thursday: Ensembles continue to show a strong
ridge developing over the region. The Inland Northwest is
expected to be in a cold stable pattern. The pattern could bring
air stagnation concerns. Morning fog will also impact the low
lying areas. Highs will be in the upper 30s and 40s. Overnight
lows will be in the upper teens and 20s. /JDC

&&

.AVIATION...
00Z TAFS: A challenging fog/low stratus forecast for tonight into
Friday morning. The boundary layer is moist with dew point
depressions within 3 degrees across much of the region. However,
there continues to be a mix of mid to high level clouds that will
limit radiative cooling and boundary layer winds will trend
northerly, which will tend to downslope off of the higher terrain
and across the basin. Best potential for fog and low clouds will
be in the sheltered mountain valleys from Colville to Sandpoint,
and down to Coeur d`Alene (KCOE). Model guidance generally keeps
low ceilings from forming around KGEG and KSFF, but light
northeast winds may act to advect low clouds into these terminals.
MVFR conditions are expected at KPUW and KLWS by late Friday
morning and into the afternoon as light northwesterly flow in the
boundary layer should pool moisture into these terminals. /SVH

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Confidence is low with the fog and low stratus forecast at TAFs
sites overnight. Model guidance is sporadic with coverage of low
cloud cover and if this will result in low stratus or fog. There
is better consensus with moderate confidence for MVFR conditions
with low stratus at KPUW and KLWS by 18Z. /SVH

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

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        30  43  26  39  32  45 /  30  30  20  20  90 100
Coeur d`Alene  31  43  29  37  32  42 /  40  40  40  40  90 100
Pullman        30  40  26  40  30  43 /  30  50  60  20  80 100
Lewiston       37  46  33  46  38  52 /  20  40  40  10  60 100
Colville       28  43  19  36  26  41 /  50  40  10  40 100 100
Sandpoint      32  41  27  35  30  39 /  80  50  50  50 100 100
Kellogg        32  41  31  35  32  39 /  30  50  60  60  90 100
Moses Lake     30  48  23  39  33  47 /  10  10   0  10  90  80
Wenatchee      34  48  27  38  34  42 /  10   0   0  20 100  80
Omak           33  48  26  38  31  40 /  20  10   0  30 100  80

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Storm Watch from Saturday morning through Monday
     afternoon for Western Chelan County-Western Okanogan County.

&&

$$