Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 230505
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1005 PM PDT Fri Mar 22 2024

.SYNOPSIS...
The mild spring weather will come to a close. Expect cooler and
wetter weather this weekend. As snow levels gradually fall this
weekend minor impacts from winter weather are forecast in the
mountains, as well as north Idaho Sunday morning. An active
weather pattern continues through next week with a series of
storms bringing mountain snow, and mainly rain in the valleys
except some snow at times overnight for the northern valleys.

&&

.DISCUSSION...
Tonight through Sunday Night: A deep low off the Oregon coast will
send a mid level wave across the region tonight into Saturday
bringing a round of valley rain and mountain snow with snow
confined to elevations mainly above 4000-5000 feet. Low level
easterly flow will provide added lift into the East Slopes of the
Cascades with forecast precipitation amounts between 0.25-0.50
for the Wenatchee area and Okanogan Valley with locally higher
amounts of 0.50-1.00" of precipitation for the East Slopes of the
Cascades. Given the recent warm spell road temperatures over the
mountain passes are expected to remain above freezing through
Saturday evening with minimal travel impacts. The exception is
Sherman Pass where a higher elevation above 5500 feet and a burst
of moderate precipitation may allow snow to accumulate on the
roads Saturday morning with around 2" in the forecast. Saturday
Night into Sunday morning the forecast gets tricky as another mid
level wave comes up from the south while interacting with a short
wave from the north and a modified arctic front that slides into
North Idaho and extreme NE Washington. Snow levels drop down to
the valley floors from Deer Park to Coeur d`Alene up into the
North ID Panhandle and as low as 2000 feet around the Spokane
area Sunday morning, while a burst of lift occurs with the arctic
front bringing a burst of snow. Given the warm ground to start,
snow is likely to only accumulate on grassy surfaces in the lower
elevations but could briefly stick to the roads under any heavier
bands. Most valleys will see an inch or less but locally amounts
of around 2 inches is possible. Here are the latest snow
probabilities from the NBM for Saturday Night into Sunday:

*Chance of at least 1" of snow: Sandpoint = 40%, Colville = 5%,
 Spokane = 0%, Coeur d`Alene = 10%

*Chance of at least 2" of snow: Sandpoint = 10%, Colville = 0%,
 Coeur d`Alene = 0%

*Chance of at least 4" of snow: Lookout Pass = 50%, Sherman Pass =
 20%

As the upper trough passes through on Sunday cooler and drier air
filters in behind it for Sunday Night bringing colder lows in the
mid 20s to mid 30s. JW


Monday and Tuesday: Portions of the Inland Northwest will remain
in a showery environment Monday and Tuesday. Our atmospheric
profile won`t feature as much conditional instability as Sunday
under the cold upper trough, but model soundings suggest enough
shallow instability for convective rain, snow, and graupel both
Mon and Tue. With weak mid and low level flow Monday, chances of
measurable precipitation are generally 30 percent or less for the
eastern third of Washington with probabilities as high as 60 or 70
percent in the Cascades and mountains of central Idaho. The
passage of an upper level disturbance on Tuesday is progged to
increase mid-level westerlies a bit raising shower coverage over
the mountainous terrain of north Idaho and along the Cascade
Crest. The National Blend of Models is generating 1 to 2 inch
accumulations in the mountains on Tuesday including the high
terrain around Lookout Pass along the ID/MT border and at Stevens
Pass on US-2 in the Cascades. Look for seasonal temperatures
Monday and Tuesday with afternoon temperatures in the mid 40s to
mid 50s. Spots like Moses Lake and Omak may touch 60 with sunshine
in the lee of the Cascades.

Wednesday: A moist frontal system on Wednesday will deliver
another round of widespread precipitation Wednesday afternoon into
Wednesday night. Compared to the system this weekend, Wednesday`s
front will move through the Pacific Northwest quicker and with
less total precipitation. Snow levels for north Idaho and
northeast Washington will be higher, too. The NBM pushes snow
levels above 4000 feet by late in the day Wednesday limiting
accumulating snow to the high elevations of north Idaho and
northeast Washington. At this time, it looks like snow
accumulations along the Cascade crest Wed and Wed night will be in
the 4 to 8 inch range with a 70 percent chance of 4 inches at
Steven Pass. Higher snow levels in Idaho cut expected
accumulations to 1 to 3 inches for Lookout Pass with a 30 percent
chance of 2 inches.

Thursday and Friday: The Northwest will likely return to a showery
regime Thursday and Friday following the passage of Wednesday
night`s front with seasonal temperatures and breezy winds. /GKoch

&&

.AVIATION...
06Z TAFS: Spotty rain will continue the next few hours before a
more organized wave moves in around 12Z bringing more widespread
precipitation. Light rain is expected at KEAT, KOMK, KMWH, and
KEPH after 06-10Z before spreading into KGEG, KSFF, KCOE, KPUW,
and KLWS near 12z. Increased moisture in the boundary layer with
the rain will result in MVFR conditions as ceilings lower for
these airports as well. Drier air pushing in from the southwest
Saturday afternoon into PUW/LWS/MWH/EAT should help raise CIGS to
VFR while the Spokane/Coeur d`Alene area up into the northern
valleys remain MVFR conditions as rain showers persist.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high
confidence of CIGS lowering to MVFR with localized IFR conditions
as rain moves in overnight through Saturday morning.

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

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        41  49  33  44  30  48 /  50  80  60  60  10  30
Coeur d`Alene  39  46  32  41  26  45 /  40  80  70  60  20  30
Pullman        43  50  36  45  30  47 /  50  70  60  80  40  50
Lewiston       46  55  41  52  35  54 /  30  70  50  80  40  30
Colville       37  47  34  48  26  48 /  40  90  80  50  10  20
Sandpoint      37  43  31  40  25  43 /  50  80  80  60  20  30
Kellogg        41  46  33  39  28  45 /  40  90  80  80  30  40
Moses Lake     44  56  38  57  35  55 /  60  60  30  30  10  10
Wenatchee      44  54  39  55  36  52 /  80  80  30  20  10  10
Omak           43  51  37  58  35  55 /  50  90  60  20  10  10

&&

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

$$


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