592
FXUS66 KOTX 242307
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
407 PM PDT Sat May 24 2025

.KEY MESSAGES...

- Warm through Sunday with widespread Minor HeatRisk.
  Temperatures warming into the 80s and low 90s by Sunday. Water
  temperatures remain cold.

- Scattered showers with a 10-30 percent chance of thunderstorms
  Sunday night into Memorial Day. Brief wind gusts to 40 mph and
  downpours possible near storms.

- Breezy winds in the 30 mph range across the Basin and Cascade
  Valleys for Sunday night into Monday.

&&

.SYNOPSIS...
Warm temperatures will be in place through Sunday with highs
into the upper 70s and low 90s. There is growing potential for
showers and thunderstorms from Sunday night into Memorial Day.
Warmer and drier weather is then expected to return for much of
next week.

&&

.DISCUSSION...
Tonight through Sunday afternoon: High pressure aloft will promote a
stable weather pattern over the Inland NW delivering warm and
dry conditions through the beginning of the holiday weekend.
High temperatures this afternoon are already running 5 to 10
degrees warmer than this time yesterday which will push
afternoon temps in the 70s to 80s today then 80s on Sunday. A
few locations in the lower Columbia Basin and Snake River Valley
will be close to 90F. The air mass is dry which will allow for
effective cooling at night with Sunday morning lows in the 40s
to lower 50s.

Sunday late afternoon through Monday: An upper-level trough and
associated cold front will slowly traverse the Inland NW
bringing an increasing risk for showers and thunderstorms while
knocking down temperatures 10+ degrees. The change in air masses
will also promote breezy conditions with wind gusts of 20-35
mph though a few gusts could be locally stronger near
thunderstorms Sunday evening.

The initial threat for isolated surface based convection and
thunderstorms will come along the spine of the Cascade Crest
Sunday afternoon and early evening. HREF indicates a 50% chance
for surface based CAPES of 400 J/kg or more along the Cascades
which will have the greatest probabilities for cell development
given the terrain and low convective inhibition (CIN). Coverage
looks be isolated but any cells that do develop could become
organized with 0-6km shear in excess of 40kts. HREF also showing
modest probabilities for SB CAPE in excess of 400 J/kg over the
Blue Mountains but with higher CIN and much lower chances for
cells to develop based solely on heating.

By Sunday evening, the threat for showers and thunderstorms increases
as the cold front slides east of the Cascades providing a
lifting mechanism. Convection will become more elevated in
nature starting in south-central WA just prior to sunset and
increasing throughout the night as the boundary limps eastward.
Main concerns will be lightning strikes and gusty outflow winds
as the rain cooled air and cooler marine air overtake inverted V
profiles (ie dry lower levels) with DCAPES in excess of 600
J/kg. HREF is showing widely scattered probabilities of 40-50%
for wind gusts in excess of 30 mph coming through the Cascade
Gaps and spreading across the Columbia Basin and into the
Palouse. Brief gusts around 30 mph seem plausible given the
cooling but if showers or storms produce rain cores prior to the
marine air arriving, would not rule out isolated gusts to 45
mph. HREF has a 5-15% for this to occur in spots. Folks out
camping for the holiday weekend should be prepared for a
potentially active Sunday night as this front comes through with
gusty winds, lightning, and showers.

As for rainfall, amounts will generally be less than a tenth for
much of the Basin given the dry lower levels and quick nature
of the cells. The slow movement of the front and training cells
from south to north will place the Okanogan Highlands, Okanogan
Valley, and areas just south on the Waterville Plateau and Upper
Basin the greatest chances for wetting rains and pockets near a
quarter of an inch.

90% of the ensembles suggest the front will push east into
W Montana Monday morning with passing showers and a few weak
thunderstorms coming through the Idaho Panhandle and E WA.
Monday will be dry for much of the region with cooler
temperatures and breezy west to southwest winds gusting 20-30
mph. The midlevel shortwave and best 500 mb cooling will track
over northern WA and N Idaho and this is where we anticipate
cumulus buildups and threat for afternoon convection. CAPEs are
not very impressive (200-300 J/kg) but still capable of a few
cells producing brief downpours and lightning strikes. Highs on
Monday will lower back into the 70s. Lakes may become a bit
choppy given the steadier winds from cool air advection.

Tuesday through next weekend: There is decent agreement in the ensembles
that shortwave ridging will return for Tuesday and Wednesday
delivering another warming and drying trend. This will be
interrupted by another shortwave and cold front on Thursday.
This feature will need be monitored closely in the coming days
for another round of thunderstorms and gusty winds. In its wake,
shortwave ridging returns to end the work week with another
period of warming and drying before yet another Pacific wave
arrives over the weekend or early next week. Confidence is not
very high for specific timing into the weekend system with large
spreads in the models. /sb

&&

.AVIATION...
00Z TAFS: High pressure aloft will deliver VFR skies and light
winds through 18z Sunday. Heads up, there will be an increasing
risk for showers and embedded thunderstorms across Central WA
Sunday evening (after 02z) with the threat shifting slowly
eastward early Monday morning.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
in VFR conditions. Moderate confidence for convection to move
into Central WA Sunday evening and night with the passage of a
cold front.

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

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        49  84  54  71  46  74 /   0   0  20  50   0   0
Coeur d`Alene  48  84  53  71  47  73 /   0   0  10  40  10   0
Pullman        48  82  51  67  45  70 /   0   0  20  40  10   0
Lewiston       53  89  58  75  51  78 /   0   0  20  30  10   0
Colville       43  83  50  72  43  76 /   0   0  40  50  20   0
Sandpoint      48  83  52  72  48  74 /   0   0  10  40  20   0
Kellogg        52  82  54  68  49  72 /   0   0  10  20  20   0
Moses Lake     50  90  57  78  47  80 /   0   0  60  20   0   0
Wenatchee      56  87  58  76  51  80 /   0   0  60  10   0   0
Omak           51  87  55  77  48  80 /   0   0  60  30  10   0

&&

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

&&

$$