790
FXUS65 KBOI 121759
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1159 AM MDT Sat Sep 12 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Warm and mostly dry today ahead of a strong cold front late tonight
  with scattered showers, isolated thunderstorms, high
  elevation snow, and gusty westerly winds.

- Breezy and much cooler Sunday, with lingering showers in
  northeast OR and the central ID mountains.

- Unsettled cool conditions through the middle of next week,
  then a warming and drying trend likely for the weekend.

&&

.SHORT TERM /Through Monday Night/...
Issued 327 AM MDT SAT SEP 12 2026
Warm and dry conditions will continue for most of the day today,
with valley high temperatures climbing to the mid 80s. A strong
low pressure system will move into the Pacific Northwest this
evening, with an associated cold front moving through the
region overnight. The cold front will initially track into
southeast Oregon by the late evening, bringing elevated
southwest winds with gusts up to 45 mph and scattered showers
over Baker County and northern portions of Malheur/Harney
County. The front will then progress into southwest Idaho
overnight, bringing wind gusts around 35 mph (ridgetop gusts up
to 45 mph) and scattered showers northeast of the Snake River
Valley. Instability remains weak with surface CAPE values less
than 100-150 J/kg, especially given the timing of the frontal
passage, but a 10-20% chance of thunderstorms will accompany
showers. The best chance for thunderstorms will be over Baker
County, OR into Valley County, ID during late evening. Models
continue to track the bulk of the moisture and the low center
north and west of the region, which further decreases potential
for precipitation accumulation. Current forecasts only show
0.25-0.50 inches of precipitation by Sunday morning, a
significant reduction compared to previous forecasts.
Temperatures will drop for Sunday by about 15-20 degrees, with
snow levels dropping down to 6,500-7,500 feet MSL. Minimal snow
will fall over higher terrain, with accumulations of less than
an inch primarily over the Wallowa/Seven Devils Mountain
Ranges. Troughing will continue through Monday, with cool
conditions lingering. Patchy valley fog will form in mountain
valleys on Sunday and Monday morning.

&&

.LONG TERM /Tuesday through Saturday/...
Issued 327 AM MDT SAT SEP 12 2026
A long wave trough will deepen into the Intermountain West
through Wednesday, bringing cool temperatures and a low chance
of showers on Wednesday into Thursday. The trough will then move
east as a ridge of high pressure will develop over the western
US by the latter half of the week. Some model disagreement
delays the trough`s exit out of the region, which would keep
cool and wet conditions lingering through the end of the work
week. However, the bulk of model solutions keep the ridge of
high pressure for the weekend, bringing above normal
temperatures and dry conditions likely for Friday into Saturday.

&&

.AVIATION /18Z Saturday through Sunday/...
Issued 1150 AM MDT SAT SEP 12 2026
VFR with increasing clouds aloft. Cold front arrives late with
increasing showers across eastern Oregon and w-central ID. A 10%
chance of lightning. Localized MVFR and mountain obscuration in
showers. Surface winds: SE-SW 5-15 kt, with gusts to 25-30 kt
this evening in eastern Oregon and Owyhee Mountains. Winds aloft
at 10kft MSL:
W-SW 20-35 kt.

KBOI...VFR. Surface winds: SE 5-12 kt. Shifting to SW-NW 10-15
kt with gusts to 25 kt around 09z/Sun with cold front.

Sunday Outlook...Generally VFR. Showers and 10% chance of
lightning across E Oregon and w-central Idaho. Localized MVFR
and mountain obscuration in showers. Patchy mountain valley fog,
mixing out by late morning. Snow levels 6500-7500 ft MSL by
Sunday morning. Surface winds Sunday: SW-NW 5-15 kt, with PM
gusts around 20-25 kt.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 9 PM MDT this evening for IDZ423-426.
OR...None.

&&

$$

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AVIATION.....JDS
SHORT TERM...SA
LONG TERM....SA