320
FXUS66 KOTX 221128
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
428 AM PDT Fri Aug 22 2025

.KEY MESSAGES...

- Warm and dry through the weekend and into next week with much
  of Central WA and the L-C Valley in areas of Major HeatRisk
  with isolated areas of Extreme HeatRisk.

- Breezy north to northeast winds Friday.

&&

.SYNOPSIS...
Temperatures will continue to warm through the weekend and remain
well above normal through mid week. Widespread high temperatures
in the mid 90s to low 100s are forecast Saturday through Wednesday
with Moderate to Major HeatRisk for far eastern Washington and
north Idaho. Major to Extreme HeatRisk is expected for central
Washington.

&&

.Discussion...
A very favorable synoptic setup is developing for a
significant late season heatwave for the Pacific Northwest. The
upper level ridge axis currently is positioned over central WA,
OR, and British Columbia sandwiched between two trofs. Over the
next 24 hours, the ridge will amplify in response to the 4-corners
high shifting west. At the surface, high pressure is
strengthening over the northern Rockies which will have an
immediate impact on our weather pattern beginning Friday morning.
Over the next few days, the surface high pressure weakens but the
ridge continues to amplify over the PacNW bringing record
temperatures along coastal areas and near record temperatures to
the interior.

With strengthening high pressure over the northern Rockies, a
surface thermal low will develop Friday over central WA and OR.
This is going to promote increasing winds from the northeast
through Friday morning hours...becoming gusty through N-S valleys
and across the Waterville Plateau. Winds are expected to
subside during the late afternoon hours as the pressure/thermal
gradient relaxes but the northeast component to the wind will
remain throughout the heatwave.

Given the increased fire activity from a few large western Montana
wildfires, the northeast wind could also increase the smoke across
north Idaho and eastern Washington through the weekend. The smoke
models have not picked up on the new activity so we don`t have a
good feel for how much smoke could invade the Inland Northwest but
I think it`s a safe bet we`ll be experiencing hazy skies at the
very least by the weekend, with the possibility of air quality
impacts depending on how active those fires remain.

Through the weekend, temperatures increase resulting in Major to
Extreme HeatRisk for many areas prompting the Excessive Heat
Watch. Since the heatwave extends for several days, overnight lows
will have a harder and harder time recovering resulting in warmer
overnight lows. While very few record high temperatures will be
broken, the Excessive Heat Watch is necessary to capture the
significance of poor recoveries night after night. Overall,
temperatures are about 15 degF above normal for this time of
year.

A useful tool to see how unusual or extreme a weather event is
the EFI (ECMWF Extreme Forecast Index). This tool highlights
coastal areas through the weekend and then the shaded region of
unusual temperatures migrates over the Cascades Sunday and then
farther inland early next week. A few interesting probabilistic
stats for this heatwave...

- 49% chance of exceeding 100 degF at KSFF Monday increasing to
  57% Tuesday and 42% Wednesday
- 2% chance of exceeding 100 degF at KGEG Monday increasing to 6%
  Tuesday and 1% Wednesday
- 92% chance of exceeding 100 degF at KLWS Friday and remains over
  60% through Wednesday
- 34% chance of exceeding 100 degF at KEAT Monday increasing to
  50% Tuesday and 26% Wednesday

Compared to previous forecasts, all of these numbers are slightly
higher so this tells me that there is increasing confidence of a
long-lived significant heatwave through midweek.

How fast the ridge breaks down late next week remains the big
question. No indications at this time that a large sweeping
change is expected but it is important to remember that some of
our most extreme fire events have occurred late in the season
after a prolonged dry spell, particularly after a heatwave. How
vigorously this ridge breaks down will be critical to watch late
next week. /AB


&&

.AVIATION...
12Z TAFS: Winds have shifted to the most part from the
northeast, with KLWS/KEAT shifting a bit later, around 15-20Z.
There is a chance KGEG/KSFF/KCOE will see some gustier winds by
15-16Z, with KCOE having the best chances and having gusts up to
22kts in the TAFs. With KGEG/KSFF, a gust up to 15kts cannot be
ruled out but prevailing winds will be around 10kts. There is
the possibility of smoke from new fires to drift into eastern
WA and northern ID because of the wind shift, but there is not
enough confidence to put smoke or haze in the TAFs right now.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
in increasing NE wind Friday morning. Low confidence that smoke
or haze will move through eastern WA and northern ID.

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

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        55  91  58  95  61  96 /   0   0   0   0   0   0
Coeur d`Alene  57  90  59  95  61  96 /   0   0   0   0   0   0
Pullman        52  91  54  96  58  94 /   0   0   0   0   0   0
Lewiston       61  98  64 102  67 102 /   0   0   0   0   0   0
Colville       45  90  49  94  51  97 /   0   0   0   0   0   0
Sandpoint      52  86  53  92  55  94 /   0   0   0   0   0   0
Kellogg        59  88  61  94  64  94 /   0   0   0   0   0   0
Moses Lake     57  94  60  98  64 100 /   0   0   0   0   0   0
Wenatchee      64  93  68  98  73 100 /   0   0   0   0   0   0
Omak           58  93  60  98  64 100 /   0   0   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
WA...Extreme Heat Watch from Saturday afternoon through Wednesday
     evening for Central Chelan County-Lower Garfield and
     Asotin Counties-Moses Lake Area-Okanogan Valley-Upper
     Columbia Basin-Waterville Plateau-Wenatchee Area-Western
     Okanogan County.
ID...Extreme Heat Watch from Saturday afternoon through Wednesday
     evening for Lewiston Area.

&&

$$