Area Forecast Discussion Issued by NWS Spokane, WA
000
FXUS66 KOTX 130402
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
902 PM PDT Tue Mar 12 2024
.SYNOPSIS...
Scattered mountain snow showers will linger over the mountains of
the Idaho Panhandle Wednesday while mostly sunny skies are in the
forecast for central and eastern Washington. High pressure will
build over the Pacific Northwest Thursday bringing an extended
period of warm and dry weather to the region through the middle of
next week.
&&
.DISCUSSION...
As of 9 PM, showers that were enhanced by afternoon
destabilization were decreasing across the Inland Northwest. The
most concentrated shower activity was was over the central Idaho
Panhandle ahead of the primary 500mb trough. For the remainder of
the night, this band currently over Shoshone, Latah, and Benewah
counties will drift to the southeast. Elevations above 3000 feet
in the Idaho Panhandle can expect additional light snow
accumulations with amounts of 1 to 2 inches across southern
Shoshone county up to Lookout Pass. Scattered snow showers will
linger into Wednesday over the mountainous terrain of north Idaho
under the the cold pool left behind the departing upper trough.
Other than some morning valley fog in northeast Washington,
central and eastern Washington will experience mostly sunny skies
tomorrow.
The Winter Weather Advisory for the Cascade Crest is scheduled to
expire at 11 PM. Another inch from a rogue shower will be
possible at the pass, but the most significant snow accumulations
will be south of Stevens Pass. The Puget Sound Convergence Zone
has migrated south of US-2 and will remain south of Stevens Pass
for the remainder of the night. Mid-level winds that determine
the orientation of the PSCZ will be northwesterly as the main
upper trough entering north Idaho drifts to the southeast. /GKoch
.PREVIOUS DISCUSSION...
Tonight: The Convergence zone is setting up and beginning to take
shape in the Cascades. Per the latest HREF and WPC guidance, the
bulk of the heaviest precipitation associated with the convergence
zone has shifted to the south of Stevens Pass. 6-hour snowfall
totals from 6 PM through Midnight are around 5-6 inches at the
Pass and up to 10-12 inches on the south side of the Pass. The 1-
hour snowfall probabilities of 1"/hour peaks between 5 PM and 7 PM
near 70%, falling to 40% from 7 PM through 10 PM. The current
Winter Weather Advisory remains in effect through late this
evening to account for this additional push of snow accumulations.
Afternoon thunderstorms have begun to blossom (as of 1 PM) across
western Washington, northern Oregon, and now some isolated storms in
the Columbia Basin are tracking northeast. Gusty winds 25-30 MPH and
even isolated 35-40 MPH gusts will be common through early
evening when the threat for thunderstorms comes to an end.
Instability across the Basin and into the West Plains has slowly
grown over the last few hours, and we`re seeing the peak of the
daytime heating, destabilization after the clear skies this
morning, and popcorn type storms popping up. The best window will
be this afternoon through about 6 PM local time for lightning,
thunder, gusty winds, and small hail.
Wednesday will see the core of the upper level trough quickly
shifting eastward, filtering cooler air east of the Cascades along
with a drier airmass. A fairly quieter weather day, we may be
faced with early morning lingering stratus in the low-lying areas
and northern Valleys where more precipitation fell and clearing
skies allowed radiational cooling to take place.
Thursday through Tuesday: A drier and warmer weather pattern will
settle into the Northwest. Daytime high temperatures this time of
year are typically low to mid 50F and our highs forecast Saturday
and Sunday will climb about 10F degrees above normal for many lower
elevation locations from Moses Lake, Omak, the West Plains, into
north Idaho. The cluster analysis of the global ensembles is quite
confident of the ridge to maintain position over the
Northwest/British Columbia through Tuesday. By mid to late next
week, there is a small percentage (about 25%) of ensemble members
that introduce a trough pushing through the Northwest. /Dewey
&&
.AVIATION...
00Z TAFS: Gusty southwest winds will continue this evening, with
gusts of 20-30 mph, before abating after 03-05Z. Convective
showers and slight chance thunderstorms (20-30%) will continue
through about 03Z, then start to wane as the primary potential
shifts into the mountains. Brief MVFR conditions are possible.
Overnight into early Wednesday low level moisture is projected to
expand some MVFR/lcl IFR low clouds/stratus/patchy fog,
especially around PUW with a risk for spreading north into the
Spokane area too. The primary threat starts after 08-10Z and
wanes after 16-18Z. Wednesday afternoon, isolated mountain
showers are possible, with marginally breezy conditions at TAF
sites (gusts to 15-20 mph).
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Moderate confidence in MVFR conditions through Tuesday evening,
with gusty southwest winds. Low confidence on thunderstorms
impacting airfields, therefore no mention in the TAFs. Moderate
confidence is MVFR conditions are PUW. Low confidence for low
clouds/fog bringing MVFR/IFR conditions into the Spokane area.
------------------------
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 29 47 28 50 30 53 / 0 0 0 0 0 0
Coeur d`Alene 29 43 26 48 28 52 / 20 20 0 0 0 0
Pullman 30 43 29 49 30 54 / 50 10 0 0 0 0
Lewiston 35 50 32 54 34 58 / 20 0 0 0 0 0
Colville 27 47 25 51 28 54 / 30 0 0 0 0 0
Sandpoint 31 41 27 46 29 49 / 30 30 0 0 0 0
Kellogg 31 39 27 47 30 53 / 60 40 0 0 0 0
Moses Lake 30 54 29 55 32 60 / 10 0 0 0 0 0
Wenatchee 33 51 33 54 36 59 / 10 0 0 0 0 0
Omak 31 53 32 56 35 60 / 0 0 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory until 11 PM PDT this evening for Western
Chelan County.
&&
$$