477
FXUS66 KOTX 151207
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
507 AM PDT Tue Sep 15 2026

.KEY MESSAGES...
- Scattered showers along the northern Washington mountains,
  and North Idaho Panhandle Tuesday.

- 20 to 40 percent chance of showers and thunderstorms Thursday
  night into Friday over Southeast Washington and the Central
  Panhandle mountains.

- Warmer temperatures Wednesday through Sunday with afternoon
  highs in the mid 70s to low 80s.

&&

.SYNOPSIS...
Cool temperatures will continue Tuesday with scattered showers
over areas of higher terrain. Temperatures rebound into the 70s
and 80s Wednesday through Sunday with mainly dry conditions.
Southeast Washington and the Central Panhandle mountains will be
the exceptions with a 20 to 40 percent chance of showers and
thunderstorms Thursday night into Friday.

&&

.DISCUSSION...
Today through Wednesday: An upper level trough developing over
British Columbia will swing south through the area later this
(Tuesday) morning through the afternoon. It will bring light rain
showers to the Cascades, northern mountains, and northern Idaho
Panhandle. Places such as Omak, Colville, Chelan, and Bonners Ferry
have a 20 percent chance and above at seeing 0.10 inches of rainfall
from Tuesday through Wednesday morning. Forcing associated with the
incoming low combined with modest instability (a couple hundred J/kg
of CAPE) will support a 10 to 15 percent chance of thunderstorms
across areas receiving rain. Soundings show saturated mid and low
levels (RH values greater than 80 percent), and PWATs near 0.7
inches. This indicates that main threats with any thunderstorms will
be isolated heavy downpours. Elsewhere, expect dry conditions.

By Wednesday, the low will shift southward and retrograde slightly
eastward. Rising heights downstream of a ridge off the Canadian
coast will promote a warming and drying trend over the Inland
Northwest. Temperatures on Wednesday will be in the mid 70s, which
is right around normal for this time of year. No precipitation is
expected.

Thursday through Monday: The aforementioned low will then begin
weakening and moving northeastward. While much of the forecast area
will continue seeing a drying trend, the low will brush far
southeast Washington and the central Idaho mountains Thursday night
into early Friday morning. Main areas impacted will be the Lewiston
and Camas Prairie areas. A 10 to 20 percent chance of
thunderstorms will accompany these light rain showers. While
PWATs will still be high, mid and low level moisture will be
lower than on Tuesday, and DCAPE values will be near 1000 J/kg.
This suggests that the main threat with these thunderstorms will
be gusty outflow winds.

After this low weakens and moves completely out of the forecast
area, high heights will dominate the weather pattern, bringing a
warming and drying trend through the weekend starting on Thursday.
Temperatures will progressively rise through the weekend, with mid
range guidance showing high temperatures reaching the 80s by Sunday.
After the brief showers Thursday into Friday, the forecast area sees
near zero chances of precipitation through the weekend. Cluster
analysis unanimously supports this warming and drying trend through
Sunday. Beyond Sunday, however, cluster analysis lowers slightly,
though 75 percent of clusters broadly show a low pressure system
approaching the coast. There is little agreement on track, strength,
and placement, but this does hint at a potential return to unsettled
weather next week. /AS

&&

.AVIATION...
12Z TAFS: All terminals have improved to VFR and are expected
to stay that way through the forecast period. A low dropping
into the area tomorrow brings a small chance of rain (HREF shows
around 10 to 20 percent) at GEG, SFF, and COE around 20Z. MWH
and EAT see chances of rain earlier - around 16Z. EAT has the
highest chances of seeing some rain showers, and these are
included in the TAF. There is a small chance of patchy fog and
lowered ceilings Tuesday morning. While HREF/RRFS probabilities
don`t support it, some BUFKIT soundings show a saturated enough
surface to support fog. There is not enough confidence to
include fog at specific terminals.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Moderate to high
confidence in widespread VFR conditions returning through the
forecast period. Low confidence in patchy fog and lowered
ceilings, which is the highest impact alternate scenario and
would require amendments. /AS

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

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        64  44  72  46  77  48 /   0  10   0   0   0   0
Coeur d`Alene  64  45  72  46  76  48 /   0  10   0   0   0   0
Pullman        65  42  73  44  72  45 /   0  10   0   0   0  10
Lewiston       71  50  77  52  77  53 /   0   0   0   0  10  20
Colville       63  37  75  39  80  42 /  40  10   0   0   0   0
Sandpoint      63  42  71  43  76  45 /  10  10   0   0   0   0
Kellogg        63  45  71  47  76  49 /   0  10   0   0   0  10
Moses Lake     66  45  75  47  79  48 /  10  10   0   0   0   0
Wenatchee      64  51  74  54  80  57 /  20  10   0   0   0   0
Omak           64  45  76  48  80  51 /  60  10   0   0   0   0

&&

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

&&

$$