022
FXUS66 KOTX 172342
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
442 PM PDT Thu Sep 17 2026

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms over southeast
  Washington and the southern to central Idaho Panhandle this
  evening.

- Warm temperatures through Monday with afternoon highs in the
  mid 70s to low 80s. Temperatures cool to near normal by the
  middle of next week.

&&

.SYNOPSIS...
Shower and thunderstorm chances return to the forecast over
southeast WA and the central ID Panhandle Thursday evening into
Friday. Afternoon temperatures will be warm through Monday with
highs in the 70s to low 80s, and overnight lows will fall into
the 40s to low 50s.

&&

.DISCUSSION...
This afternoon through Saturday: An upper level low pressure system
will track from eastern Oregon today into eastern Idaho by Saturday.
Moisture pushing north ahead of this low will bring up moisture with
up to a 50% chance of showers across the southeast portion of the
forecast area through this evening. Mid level lapse rates also
steepen with an isolated thunderstorm threat with these showers as
well. Best instability will generally be over the higher terrain of
the Blue Mountains in northeast Oregon to the Clearwater Mountains
in the southern Idaho Panhandle. Storms will then be moving into an
environment that won`t be as conducive for continuing to support
thunderstorm development as the push further north into places like
the the Palouse to the Silver Valley. Decaying convection will still
have the potential to produce at least occasional cloud to ground
lightning strikes gusty outflow winds up 30 mph, and brief heavy
downpours. Latest convective allowing model guidance has weakened
the potential outflow boundary produced by the convection this
evening. It`s not completely out of the question that blowing dust
will occur with the winds, but chances look much less likely
compared to what these models were indicating this time yesterday.
Showers are expected to continue into the evening, but the
convective potential will be decreasing as we lose the surface
heating. As such, I expect shower coverage to be less over the
southeast portion of the forecast area, and the potential for
thunderstorms will rapidly decrease as well.

We won`t be as unstable on Friday and Saturday as the low makes its
march eastward across Idaho. The fringes of the southeast portion of
our forecast area will continue to see the potential for diurnally
forced convection in near the Camas Prairie and in the St. Joe
Forest in the Central Panhandle Mountains. Otherwise, it looks like
we won`t be unstable enough for convection to initiate off of the
higher terrain further north and west, e.g. over the Palouse.
Temperatures will remain warm and above average into the weekend.
Cloud cover also will be on the decrease as the upper level pulls
away.

Saturday night through Thursday: Good agreement among the model
ensembles with a ridging of high pressure building in over the
region into early next week. This will keep our temperatures warm
with highs in the upper 70s to low 80s. Models also are generally in
good agreement with the overall longwave pattern with troughing of
lower pressure in the eastern Pacific and ridging of higher pressure
over the Rockies. Where models disagree and uncertainty is
introduced is how close in proximity the trough will be to the
Northwest region. The general consensus is that temperatures
will be cooler starting Tuesday into Wednesday, but how much
cooler is still very much up in the air. Right now it is 50/50
if we see cooler than average temperatures with an increased
chance for showers, particularly over the Cascades, or continue
with a dry forecast with temperatures at or slightly above
normal for Thursday into Friday next week. /SVH

&&

.AVIATION...
00Z TAFS: A low pressure system spinning over eastern Oregon
will spread scattered showers with a isolated embedded
thunderstorms into southeast Washington and the southern Idaho
Panhandle into the evening. Instability parameters are less
likely to support thunderstorms as far north as KPUW with
chances decreasing to a 15% chance. Chances decrease further
north and west into KMWH/KGEG/KSFF/KCOE where spread mid to high
level clouds from convection is all that is expected at these
airport terminals. Thunderstorms will be capable of gusty
outflows of up to 20-25 kts and brief heavy downpours. Isolated
showers in the vicinity of KLWS and KPUW will continue
overnight, but convection is expected to weaken.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: An outflow
boundary is evident on radar in SW Spokane county with south
winds gusting up to 20 kts. This is expected to weaken as it
approaches GEG through 02z but a brief wind shift out of the
south-southwest is an alternate scenario. JW

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

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        52  77  50  79  52  81 /   0   0   0   0   0   0
Coeur d`Alene  50  75  50  77  51  79 /   0   0   0   0   0   0
Pullman        49  73  48  75  48  79 /  30   0   0   0   0   0
Lewiston       56  78  55  81  56  84 /  30   0   0   0   0   0
Colville       43  79  43  81  45  82 /   0   0   0   0   0   0
Sandpoint      45  73  47  76  49  77 /   0   0   0   0   0   0
Kellogg        50  73  50  75  51  77 /  10   0   0   0   0   0
Moses Lake     49  79  50  80  51  82 /   0   0   0   0   0   0
Wenatchee      56  79  58  79  59  80 /   0   0   0   0   0   0
Omak           50  80  52  80  53  81 /   0   0   0   0   0   0

&&

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

&&

$$