122
FXUS65 KBOI 010251
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
851 PM MDT Sun Aug 31 2025

.DISCUSSION...Virga showers are moving into Harney County this
evening, still a 10-20% chance of a stray lightning strike in
the area tonight. Otherwise, conditions are warm and hazy from
wildfire smoke. Temperatures will be hot tomorrow, about 10-15
degrees above normal with cumulus buildups over higher terrain.
A 10-20% chance of showers over the Owyhee Mountains is expected
tomorrow afternoon, thanks to some increasing moisture from the
south. No updates necessary to the forecast.

&&

.AVIATION...Generally VFR. Smoke layers aloft through around
20kft MSL. A 10-20% chance of virga showers/thunderstorms in
Harney County (KBNO) this evening, tapering off by early
morning. The Owyhee Mountains will also see a 10-20% chance of
virga showers/thunderstorms tomorrow afternoon. Surface winds:
S-E 5-15 kt with localized gusts to 25 kt in the Lower Snake
Plain tomorrow afternoon. Winds aloft at 10kft MSL: S-SE 10-20
kt.

KBOI...VFR. Smoke layers aloft creating hazy skies. Surface
winds: E-SE 8-10 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Tuesday night...A strong ridge
continues across the Pacific Northwest. Cumulus clouds are
beginning to develop over the terrain, with the greatest
coverage at 2 PM MDT across Harney County. This area and the
higher terrain of Baker County have the best chance for
thunderstorm development through 6 PM MDT, with probabilities
around 15 percent. Any storms that do form will be high based
and capable of producing gusty outflow winds up to 40 MPH with
little rainfall. Conditions remain stable enough to limit
thunderstorm activity across southwest Idaho this afternoon and
evening, though cumulus buildups can still be expected over the
mountains.

Hot temperatures are expected on Labor Day, with the Upper
Treasure Valley forecast to reach near 100 degrees with
increasing southeasterly winds ahead of a thermal trough. This
would be about 15 degrees above normal for early September.
Cumulus development is again expected over the higher terrain,
with a slight chance of thunderstorms (around 15 percent) from
the Owyhee Mountains south to the Nevada border.

By late Monday into Tuesday, the ridge axis shifts eastward
over southwest Idaho, allowing southerly flow aloft to set up.
This will draw deeper moisture northward, pushing precipitable
water values above 0.75 inches. Hot surface temperatures
combined with dynamic lift from an approaching weak embedded
shortwave Tuesday afternoon and evening will create favorable
conditions for thunderstorm development (20-30% chance) across
southeast Oregon and areas south of the Snake Plain in Idaho.
The threat for thunderstorms will continue into Wednesday
morning as the shortwave lifts from south to north across east
central Oregon. These storms will be capable of producing gusty
outflow winds up to 45 MPH.

Smoke from fires in central Oregon has increased across the
region today as it is being recirculated around the ridge from
the east. Strengthening southerly flow Monday into Tuesday
should keep additional smoke from the Emigrant Fire northwest of
the area. However, smoke from larger fires in eastern
California will be transported northward, and as a result,
little improvement in smoke and haze is expected through
Tuesday.

LONG TERM...Wednesday through Sunday...Guidance continues to
support a low center tracking through central Oregon through
Wednesday. With added forcing from this feature, and sufficient
moisture coming in from southerly flow aloft, have opted to nudge up
precipitation chances come Wednesday evening (10-20% across eastern
Oregon and higher terrain in southwest Idaho). While deterministic
guidance doesn`t show much Wednesday afternoon, ensemble guidance
seems to be picking up on the chances better. While our area will
remain under an upper-level ridge beyond Wednesday, this ridge will
begin to break down by late week. As a trough begins to move onshore
late in the week, temperatures will begin to cool and precipitation
chances will begin to increase area wide, with a 10-30% (10-20%)
chance of showers (afternoon thunderstorms) across much of our area
Friday through Sunday. Temperatures will be around 5-10 degrees
above normal Wednesday through Friday, before cooling to near normal
Saturday and Sunday.

&&

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

&&

$$

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