Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 120439
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
939 PM PDT Mon Mar 11 2024

.SYNOPSIS...
Another round of rain and snow lingers on through Tuesday evening
bringing additional mountain snow to the region and lowland rain.
High pressure will build over the Pacific Northwest Thursday into
next weekend bringing warmer temperatures and dry weather.

&&

.DISCUSSION...
Happening now: Afternoon rain showers across eastern Washington into
northern Idaho are increasing in coverage but are more of the
isolated to widely scattered shower type. Conditions are more
favorable today for rain showers and rain/snow mix in higher
elevations while our snow accumulations remain in the mountains
above 3000-3500 feet.

Tonight through Tuesday night: The negatively tilted upper level
trough will slide southeast through Oregon and Idaho tonight through
Tuesday. The plume of moisture as seen from satellite off the West
coast this afternoon will continue to push moisture east. The Inland
Northwest will remain in a west to southwest flow pattern aloft
which will favor our Cascade Crest area (Stevens Pass) for
persistent precipitation accumulations as well as our Idaho
Panhandle mountain pass area (Lookout Pass). Given our temperatures
aloft today are cool but not as cold as we will see tomorrow (-21C
compared to -32C Tuesday), there is very little chance (less than
10%) for thunderstorms today.

The band of precipitation associated with the cold front will push
east bringing widespread showers across Washington and north Idaho.
By Tuesday morning, the band will be well into Idaho and moving into
Montana, leaving the Waterville Plateau and part of the Columbia
Basin in a shadow. As the upper low pivots across the Cascades
Tuesday afternoon and evening, a convergence zone of precipitation
will setup in the Cascades. Organized enough for several hours, the
HREF guidance carries a 20-25% chance for 1"/ hour of snow at
Stevens Pass between 5 pm and 10 pm. The snow accumulations have
changed slightly and will continue to change given the convective
nature of a convergence zone, but a range of 12-18" for Stevens Pass
seems reasonable with the 90th percentile at 12-14" and the 25th
percentile at 7-8". Timing will also take into consideration the
cold core aloft that will aid in producing quicker snowfall rates.
Shifting east, Lookout Pass in Idaho will experience slightly lower
rates but still be impacted by the cold upper level system through
Wednesday morning.

Wednesday the upper level system will dig south and we will be faced
with building high pressure from a ridge from the west. While clear
skies won`t be widespread until Thursday, temperatures will be on
the rise Thursday through the weekend. Normal high temperatures for
mid March range from low to upper 50s and by Saturday most of the
Inland Northwest will see temperatures reaching a few degrees above
normal and continuing a warming trend into early next week of above
normal temperatures. /Dewey

&&

.AVIATION...

06Z TAFS: spotty shower exit ahead of an incoming band incoming
band of more stratiform low elevation rain that is filling in on
radar and expected to have its impact spread over 08Z Tuesday
with the back edge potentially clearing the aviation area near 15Z
Tuesday. MVFR or brief IFR ceilings and visibilities and mountain
obscurations possible the stable precip. Gusty southwest winds
follow with the passage of the back edge of the boundary and is
followed up with some surface based convective showers between 20Z
Tuesday and 02Z Wednesday with stabilization and decreasing clouds
after. /Pelatti

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Moderate to high confidence in MVFR conditions with precipitation
onset in more stratiform rainfall tonight mainly between 08-15Z
Tuesday along with the Tuesday afternoon and evening gusty
southwest winds. /Pelatti

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

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        37  48  29  47  28  50 /  80  80  30   0   0   0
Coeur d`Alene  36  45  29  43  25  47 /  90  90  50  10   0   0
Pullman        37  47  29  43  28  48 /  80  80  40  10   0   0
Lewiston       41  55  35  50  32  53 /  60  70  20  10   0   0
Colville       34  46  26  47  25  50 /  80  80  40   0   0   0
Sandpoint      36  41  30  41  27  44 /  90  90  60  20   0   0
Kellogg        37  43  30  40  26  45 /  90  90  70  30   0   0
Moses Lake     36  53  29  53  29  55 /  70  30   0   0   0   0
Wenatchee      36  50  32  52  33  54 /  80  20   0   0   0   0
Omak           38  52  30  53  32  54 /  80  30  10   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Weather Advisory from 8 PM this evening to 11 AM PDT
     Tuesday for Central Panhandle Mountains.

WA...Winter Weather Advisory until 11 PM PDT Tuesday for Western
     Chelan County.

&&

$$


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