395
FXUS65 KBOI 290842
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
242 AM MDT Sat Aug 29 2026

.KEY MESSAGES...
- Isolated showers and thunderstorms today. Stronger storms
  producing gusty winds possible in SW Idaho.

- Cool and dry Sunday then warmer early next week.

- A deeper low pressure system expected later next week for
  cooler and wetter conditions.

&&

.SHORT TERM /Through Monday Night/...
Upper level low over the Pacific Northwest today will keep mid
level moisture across the forecast area. Sub-cloud moisture
combined with steep low level lapse rates this afternoon should
foster convective development. While widespread severe weather
is not anticipated, isolated strong thunderstorms over southwest
Idaho, mainly south of a Rome-Ontario-Stanley line, could
produce localized outflow wind gusts up to 55 mph along with
brief heavy rain. Convective activity will taper off across
eastern Oregon late this afternoon, while shower and
thunderstorm chances persist across central and southern Idaho
into the evening hours.

A broader upper level trough and cold front will advance from
the Pacific Northwest late Saturday into Sunday morning. Latest
high-res model guidance has significantly lowered the convective
threat ahead of the front across the West-Central Mountains
Saturday evening to the point where most have removed showers
and thunderstorms altogether. The cold frontal passage late
Saturday evening into Sunday morning will usher in cooler, drier
air along with gusty northwest winds across the region. High
temperatures on Sunday will drop 5 to 10 degrees below seasonal
averages with patchy frost possible Sunday and Monday morning
across the higher valleys of southeast Oregon.

Brief shortwave ridging on Monday will allow temperatures to
rebound back toward normal levels, though shower chances will
begin to return to south central Idaho late Monday night with
the approach of the next upper level low pressure system.

&&

.LONG TERM /Tuesday through Saturday/...
The long term period will feature an active and persistent
trough pattern across the western United States. An amplifying
trough off the Pacific Northwest coast will push another
shortwave disturbance inland on Tuesday, bringing increased
chances for showers and thunderstorms, mainly across the higher
terrain.

A stronger closed low will dig along the trough axis Wednesday
through Friday, stalling near the Pacific Northwest coast. This
positioning will keep southeast Oregon and southwest Idaho under
cool, unsettled southwesterly flow aloft. High temperatures will
fall roughly 10 degrees below normal for early September, with
valley highs remaining in the 70s. Tightening surface pressure
gradients and strong mid level winds mixing down each afternoon
will generate widespread breezy to windy conditions Tuesday
through Saturday. Shower and thunderstorm timing will remain
tied to minor individual shortwaves rotating around the parent
trough.

&&

.AVIATION /06Z Saturday through Sunday/...
Issued 1205 AM MDT SAT AUG 29 2026
Isolated to scattered light rain showers and virga across S Idaho
and far SE Oregon will continue overnight into Saturday. Isolated
thunderstorms will also develop with gusty erratic winds 25-45 kt
possible on Saturday. Local reductions in visibility from wildfire
smoke. Surface winds: SE-W 5-15 kt, becoming NW Saturday evening
along a cold front. Localized gusts 15-25 kt overnight, with gusts
20-30 kt Saturday afternoon/evening. Winds aloft at 10kft MSL: SW 15-
25 kt.

KBOI...Overcast mid to high clouds. Occasional light showers/virga
in the vicinity through Saturday, with a 10% chance of a
thunderstorm late afternoon/evening. Surface winds SE 5-15 kt with
gusts up to 25 kt overnight, becoming light and variable to NW by
Saturday morning.

Sunday Outlook...Decreasing clouds and dry. Surface winds W-NW 5-15
kt, afternoon gusts 20-25 kt in S-central Idaho.

&&

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

OR...None.

&&

$$

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SHORT TERM...JDS
LONG TERM....JDS
AVIATION.....ST