917
FXUS66 KOTX 311121
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
421 AM PDT Sun Aug 31 2025

.KEY MESSAGES...

- 10-15% chance for sprinkles today. 15-30% chance for showers
  and dry thunderstorms Sunday night in Central Washington.

- Hot temperatures next week, locally near 100, with Major to
  locally extreme HeatRisk. Record high temperatures for
  September possible for multiple locations.

&&

.SYNOPSIS...
Today will feature scattered clouds and sprinkles. There is a
risk for showers and dry thunderstorms tonight in Central WA. A
strong ridge of high pressure will begin to build in this
weekend. Hot temperatures return with the ridge that will extend
through next week. High temperatures will climb back into the
upper 90s to near 100 degrees.

&&

.DISCUSSION...

HOT WEATHER WITH WIDESPREAD MAJOR HEATRISK NEXT WEEK...

Labor Day Weekend: A deep low has taken residence along the WA
Coast with height rises ongoing over the Inland NW. Sunday will
be 2-5 degrees warmer than Saturday with areas of North Idaho
and far eastern WA closer to that 5 degree warmer mark and
Central WA closer to 2-3 warmer. The delay in warming over
Central is due to the offshore low wobbling slightly inland and
shifting the ridge axis into Western MT temporarily. As this
occurs, increasing southerly flow will draw mid and high level
moisture into the region. This has been ongoing this evening
with scattered to broken midlevel clouds and even some virga
showers noted on a few of the cams. There is increasing
confidence for a weak wave to swing around the low and track
through Central WA Sunday night into early Monday morning. NAM,
which does well with elevated instability, is indicating upwards
of 300-600 j/kg of elevated CAPE for this wave to work with
with increasing concern for high based showers and thunderstorms
over Central WA Sunday night. More models are latching on to
this and showing a smattering of a few hundredths. Sub-cloud
layers will remain very warm and dry such that wetting rains are
not expected with any convection. Lightning activity is
expected to be isolated due to the forecast strength of this
wave but given the instability present, if this wave is stronger
than expected, would not rule out scattered coverage. Main
concerns with this activity will be new fire starts and brief
outflow winds around 20 mph. The main focus will be over Central
WA roughly west of a line from Republic to Moses Lake however
there is a small threat (~10%) for a few cells to develop in the
evening near the Idaho/Montana border between Libby, Bonners
Ferry, and into NE WA around Ione.

This wave will lift out of the region early Monday morning and the
low over Western WA will start to retrograde into the Pacific.
The ridge axis will slowly retrograde as well and settle back
into the Eastern WA by Tuesday morning. Temperatures on Monday
will be similar to Sunday with widespread 90s. No precipitation
is expected Monday and winds will be light. Areas of haze and
smoke that are present Sunday will likely linger over the region
into Monday given the light winds.

Tuesday through Saturday: A multi-day heat wave is on tap for the
Inland NW under the influence of a strong upper-level ridge.
Temperatures warm another 1-2 degrees going into Tuesday and
remain hot through the week. Several record high temperatures
will be in jeopardy between Monday and Thursday for afternoon
highs and warm overnight lows. High temperatures will be solidly
in the 90s to lower 100s with overnight lows in the 60s and
some 70s. Folks should plan for moderate to major heat risk as
we go through next week and take proper measures to avoid heat
related illnesses such as staying hydrated and seeking breaks in
air conditioning and/or shade during the hottest part of the
day. During the heat wave, some models indicate a midlevel
circulation getting cut off and drifting around under the ridge
around WED-THU. Still not seeing much in the way of
precipitation from this feature but something to monitor. The
one wildcard that could keep temperatures cooler than expected
would be if thicker smoke were to settle into some areas. Smoke
is effective at keeping afternoon temperatures cooler than
forecast but does not trap longwave radiation which is released
at night allow for cooling. This is tough to forecast at this
point though the upcoming heat and drying will be favorable for
increased fire activity for ongoing fires.

There remains a great deal of uncertainty with the
evolution/breakdown of the ridge Friday into the weekend as
several low pressure systems undergo phasing over the Pacific
and into the Gulf of AK. There is moderate confidence that the
ridge axis will shift eastward but low confidence, how far.
Forecast indicates subtle cooling each day but this is largely
driven by the mean starting to lower as spread in potential
daily temperatures expands closer to 10+ degrees. In addition to
temperatures, there is low confidence how this will equate to
precipitation chances heading into next weekend. I am
anticipating some degree of increasing winds, especially in the
lee of the Cascades as the cross Cascade gradient restrengthens
but little confidence in a significant region-wide wind event at
this time. Stay tuned. /sb

&&

.AVIATION...
12Z TAFS: VFR conditions will prevail through the period. Areas
of haze will continue to bring visibility down to 7-9SM with
localized areas decreasing to 6SM. Mid and high level clouds
will stream in from the south with small chances for spotty
sprinkles at times. Local speeds near 10kts expected at KCOE,
KPUW, and over portions of the Columbia Basin.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
High confidence in VFR conditions at the TAF sites. High
confidence in smoke resulting in haze for
GEG/SFF/COE/MWH/LWS/PUW beginning at varying times but low
confidence it will be thick enough to drop visibilities to 6SM.

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

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:/weather.gov/otx/avndashboard

&&

.Preliminary Point Temps/PoPs...
Spokane        97  63  96  64  99  64 /  10  10   0   0   0   0
Coeur d`Alene  95  65  97  65  99  64 /  10  10   0   0   0   0
Pullman        95  60  95  59  97  60 /  10  10   0   0   0   0
Lewiston      100  68  99  68 101  69 /  10  10   0   0   0   0
Colville       95  54  96  55 100  55 /  10  20   0   0   0   0
Sandpoint      91  60  95  58  98  58 /  10  20   0   0   0   0
Kellogg        93  67  96  67  98  67 /  10  10   0   0   0   0
Moses Lake     95  63  93  61  98  63 /  10  20  10   0   0   0
Wenatchee      95  68  93  70 100  72 /  10  20   0   0   0   0
Omak           96  68  98  67 100  67 /  10  20   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from 1 PM this afternoon to 8 PM PDT Thursday
     for Lower Garfield and Asotin Counties-Okanogan Valley-
     Spokane Area-Upper Columbia Basin-Waterville Plateau-
     Wenatchee Area.
ID...Heat Advisory from 1 PM this afternoon to 8 PM PDT Thursday
     for Coeur d`Alene Area-Lewiston Area.
     Air Quality Alert until 10 AM PDT Tuesday for Lewis and
     Southern Nez Perce Counties-Lewiston Area.

&&

$$