588
FXUS65 KBOI 020236
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
836 PM MDT Mon Sep 1 2025

.DISCUSSION...A few virga showers are still moving through the
Upper Treasure Valley and near Burns, OR as of 8:20pm MDT,
otherwise just a few remnant cumulus clouds and hazy skies.
Temperatures peaked at 100F in Boise this evening, just two
degrees off of the daily record. Temperatures look to creep up
to 1-2 degrees below where they were today across the region,
with a 10-20% chance of afternoon showers and thunderstorms
near the Nevada border and over the Owyhee Mountains. Hazy skies
thanks to smoke from Oregon wildfires will continue to affect
the region tomorrow. Updated probability of precipitation for
the showers this evening, otherwise no forecast updates.

&&

.AVIATION...VFR. Smoke layers aloft through 20kft MSL. High
density altitude Tue afternoon due to hot temps. Virga and
isolated showers/thunderstorms near NV border and in SE Oregon
after Tue/20Z, capable of 30-40 kt gusts. Surface Winds:
variable 5-15 kt. Winds aloft at 10kft MSL: S to E 5-15 kt.

KBOI...VFR. Light smoke layers aloft. High density altitude
Tuesday afternoon due to hot temps. Surface winds: E-SE 3-10 kt,
transitioning to NW 3-8 kt around Tue/17Z.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Wednesday night...A strong ridge
remains in place across the Pacific Northwest with the ridge
axis positioned just to the west. This setup will keep
temperatures well above normal and near record levels with highs
in the Treasure Valley expected to reach around 100 degrees
again on Tuesday.

Radar as of 2 PM MDT shows, showers and thunderstorms
developing along the Idaho/Nevada border. Activity is expected
to continue through the remainder of the afternoon across
Owyhee, Twin Falls and Malheur Counties. A few thunderstorms may
also develop over parts of the central Idaho mountains later
this afternoon. Any Storms that do form will be high based and
capable of producing gusty outflow winds up to 40 MPH with
little rainfall.

On Tuesday, the ridge axis shifts eastward over southwest
Idaho, allowing southerly flow aloft to develop. This will draw
deeper moisture northward, with precipitable water values rising
to near 0.75 inches. Combined with hot surface temperatures and
an approaching shortwave from the southwest, the environment
will become more favorable for thunderstorms. The best chance
for thunderstorms (20 to 30 Percent) is across southeast Oregon,
with additional storms possible south of the Snake River Plain.
Storms may initiate later in the afternoon with the latest
guidance slowing the shortwave`s progression through Oregon.
Storms may linger into Tuesday night and early Wednesday
morning, capable of producing gusty outflow winds up to 45 MPH.

Temperatures will cool by 5 to 8 degrees on Wednesday as the
ridge weakens with the shortwave passage. Enough moisture is
expected to linger near the Nevada border to support afternoon
thunderstorms.

LONG TERM...Thursday through Monday...The upper-level ridge
over our area will begin to breakdown late this week. However,
there are some differences in guidance regarding how fast this
breakdown occurs. The GFS solutions have an upper low infringing
on our area as early as Thursday afternoon, with southerly flow
aloft advecting moisture in (PWATs surpassing an inch). The
Euro solutions are significantly slower in bring the trough
onshore. With a blocking pattern going to be in place (dare I
say omega block), am leaning towards the slower timing with the
ridge breakdown occurring over the weekend. In either case,
south to southwesterly flow aloft will act to advect moisture
in, with the GFS (Euro) ensemble mean increasing to 0.9-1
(0.8-0.9) inches by Friday. With moisture lingering around
through Monday, this supports a 20-50% chance of showers and
15-25% chance of afternoon showers Friday through Monday. Heavy
rain may be a concern this coming weekend. Temperatures will
take on a cooling trend, reaching near normal Sunday and Monday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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DISCUSSION...SA
AVIATION.....SH
SHORT TERM...JDS
LONG TERM....NF