484
FXUS65 KBOI 122359
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
559 PM 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 216 PM MDT SAT SEP 12 2026
A strong low pressure system will move into the area this
evening, with an associated cold front putting an end to the
warm and dry conditions we`ll see most of the day. Ahead of the
front, this evening most of the high desert will see peak wind
gusts 25 to 35 mph out of the southwest. Late this evening, as
the front begins to track through Southeast Oregon,
precipitation chances increase near the Blue Mountains, and wind
gusts along ridges and highlands increase to 30 to 45 mph.
Inside scattered showers, an isolated weak thunderstorm is
possible. The front, winds, and precipitation move into
southwest Idaho overnight. Thunder chances mostly subside
overnight while gusts up to 45 mph remain possible along the
highest ridges. Precipitation stays mostly north of our area,
with only a 10- 20% in northern Valley County. The rainfall
forecast continues to trend downwards, but with ~0.1 inches
still possible in the Blue Mtns and Mtns north of McCall.
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 216 PM MDT SAT SEP 12 2026
A broad trough remains in place over the region. This will
allow a weak upper level trough and accompanying dry cold front
to cross the area. Limited moisture will keep precipitation
chances near zero, but the frontal passage will generate breezy
conditions, especially across the Snake River Plain and high
terrain. High temperatures on Tuesday will remain slightly below
seasonal normals behind the front.

By Wednesday, an upper level ridge begins building over the
Intermountain West. Heights and temperatures aloft will steadily
increase through the end of the week, yielding a clear warming
and drying trend from Wednesday through Saturday. Temperatures
will rise to 5 to 10 degrees above normal by Friday and
Saturday. Model guidance shows high confidence in stable
conditions under the ridge, with light diurnal winds and minimal
cloud cover prevailing across the region through the remainder
of the period.

&&

.AVIATION /00Z Sunday through Monday/...
Issued 552 PM 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 near KBKE. Localized MVFR and mountain
obscuration in showers. Lingering clouds but no precipitation on
Sunday. Surface winds: SW to W 5-15 kt, with gusts to 25-30 kt
this evening and early Sunday in eastern Oregon and Owyhee
Mountains. Winds aloft at 10kft MSL: SW 25-45 kt.

KBOI...VFR with BKN mid-level clouds. Surface winds: SE 5-12
kt. Shifting to WNW 10-15 kt with gusts to 25 kt around 09z/Sun
with cold front.

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

&&

$$

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AVIATION.....JR
SHORT TERM...JM
LONG TERM....JDS