361
FXUS66 KOTX 310541
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1041 PM PDT Sat Aug 30 2025

.KEY MESSAGES...

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

&&

.SYNOPSIS...
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 ridge building over the US west coast has
warmed temperatures into the high 80s and low 90s, which is ten
degrees higher than normal for this time of year. The low pressure
system sitting just off the PNW coast will meander eastward and into
the area Sunday night. The lift from this low combined with warmer
temperatures has the NBM showing 5-15 percent chance of
thunderstorms in the Cascades, with chances stretching as far east
as Omak. Main impacts from these thunderstorms will be lightning
induced fire starts, gusty outflow winds, and locally heavy rainfall
rates. Most CAMs are showing this to be afternoon into evening and
overnight convection. Sunday, temperatures will warm a bit further,
and by Monday will warm more. Even before the ridge starts
strengthening later in the week, these warming temperatures have the
Okanogan Valley, Wenatchee, Waterville Plateau, upper Columbia
Basin, Spokane/Coeur d`Alene, and lower Garfield and Asotin county
areas seeing widespread moderate to major Heat Risk. Given this, and
the fact that this is a holiday weekend and a lot of people will be
taking to outdoor activities, a Heat Advisory has been issued for
these areas from 1pm PDT Sunday through 8pm PDT Thursday.
Additionally, smoke from fires down south is moving its way
northward into our area, which will result in haze throughout at
least Sunday and Monday.

Tuesday through Thursday: The ridge starts building further over the
Pacific Northwest, and the low pressure system will begin
retrograding westward, allowing heights to build up even further.
When these heights peak on Wednesday, they will be anomalously high
for this time of year. With the subsequent increase in 850mb
temperatures, widespread Major to locally Extreme Heat Risk will be
seen throughout much of the area. Temperatures are projected to get
into the high 90s, with some lower valley areas getting into the
triple digits by Tuesday and continuing through Thursday. Tuesday
and Wednesday look to be the hottest days of this warmup. NBM
probabilities for temperatures reaching 100 degrees currently sit at
over 50 percent for a large part of the area Tuesday and Wednesday.
For the Spokane/Coeur d`Alene area, probabilities of hitting triple
digits sit at 70 percent and above. For Wednesday, these chances
decrease to 45 percent and above, but are still quite high for this
time of year. As these forecasted highs stand, some places could see
monthly records broken for September. Smoke models show a good
chance of haze remaining through the week, introducing the
possibility of a decline in air quality during this extended late
summer season heat wave. There is a very good chance that areas will
get added to the Heat Advisory in the coming days as things warm
further, with some areas possibly getting upgraded to an Extreme
Heat Warning, especially places that are anticipated to see Extreme
Heat Risk, such as Wenatchee. With Major Heat Risk, and temperatures
being this high for an extended amount of time, almost everyone
without access to adequate hydration and cooling will be at risk of
heat-related illnesses.

As temperatures warm, relative humidity will drop. By Tuesday,
values will drop into the low teens. With high lapse rates at 8
degC/km and some local 9 degC/km, all signs are pointing to a hot,
dry and unstable atmosphere for fire weather, which could lead to
increased fire activity. We will keep a close eye on this as things
progress to see if a need arises for any fire weather headlines.

Friday through Sunday: Unfortunately, many long range models are
still showing temperatures in the high 80s and low 90s Friday
through next weekend. Cluster analysis is very agreeable on
anomalously high heights staying over the area Friday and Saturday.
Heat Risk values on Friday still indicate widespread Moderate to
locally Major Heat Risk, which could lead to an extension in any
heat products should temperatures warm further or Heat Risk rises to
Moderate for more areas. On Sunday, agreement splits, with half of
the clusters favoring continued warm conditions and half the
clusters favoring a cooldown with the possibility of some rain. /AS

&&

.AVIATION...
06Z TAFS: VFR conditions will prevail through the period. Areas
of haze will continue to bring visibility 7-9SM locally down to
6SM. Mid and high clouds will stream in from the south with
small chances for spotty sprinkles at times. Winds will swing
around to more of an easterly direction overnight and Sunday.
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 to reach 6SM. /sb

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

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        62  97  64  97  64  99 /   0   0   0   0   0   0
Coeur d`Alene  62  97  64  97  64  99 /   0   0   0   0   0   0
Pullman        61  95  60  96  59  97 /   0   0   0   0   0   0
Lewiston       68 102  68 101  68 101 /  20   0   0   0   0   0
Colville       51  95  54  96  55  99 /   0  10  10   0   0   0
Sandpoint      56  92  59  94  58  96 /   0   0   0   0   0   0
Kellogg        64  94  67  96  67  97 /   0   0   0   0   0   0
Moses Lake     64  96  63  95  63 100 /   0  10  10   0   0   0
Wenatchee      68  95  70  94  70 100 /  10  10  20   0   0   0
Omak           64  97  67  97  67 101 /   0  10  20   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Heat Advisory from 1 PM Sunday 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 Sunday 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.

&&

$$