Area Forecast Discussion Issued by NWS Spokane, WA
000
FXUS66 KOTX 122157
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
257 PM PDT Tue Mar 12 2024
.SYNOPSIS...
A round of mountain snow and lowland rain showers and storms
through Tuesday evening. High pressure will build over the
Pacific Northwest Thursday bringing warmer temperatures and dry
weather through early next week to the Inland Northwest.
&&
.DISCUSSION...
Today and 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...
18Z TAFS: Gusty southwest winds will accompany the frontal passage
during the late morning and afternoon hours today, gusts 20-30
mph. Surface based convective storms are forecast this afternoon
from about 12 pm through 8 pm for eastern WA and the ID Panhandle.
Airfields most likely to be impacted by brief heavy downpours,
gusty winds, and brief MVFR/IFR conditions due to storms include
GEG, SFF, DEW, COE, CQV, SZT, and PUW. Thunderstorm potential
across the region is around 20-30%. Wednesday morning lingering
moisture could generate fog/stratus resulting in brief IFR
conditions for the northern valleys and DEW.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Moderate to high confidence in MVFR conditions with precipitation
onset in more stratiform rainfall through Tuesday afternoon and
evening gusty southwest winds. Low confidence on thunderstorms
impacting airfields, therefore no mention in the TAFs. Low
confidence for fog bringing IFR conditions into the Spokane area.
/Dewey
------------------------
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 / 50 0 0 0 0 0
Coeur d`Alene 29 43 26 48 28 52 / 70 20 0 0 0 0
Pullman 30 43 29 49 30 54 / 40 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 / 60 0 0 0 0 0
Sandpoint 31 41 27 46 29 49 / 80 30 0 0 0 0
Kellogg 31 39 27 47 30 53 / 80 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 / 10 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.
&&
$$