059
FXUS65 KBOI 210411
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1011 PM MDT Sun Sep 20 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Mostly dry with warming temperatures through Thursday.

- Chance of showers and thunderstorms Tuesday, mostly across
  higher terrain of southwest Idaho.

- Cooler temperatures heading into next weekend with a chance of
  precipitation across SE Oregon and portions of SW Idaho
  Friday.

&&

.SHORT TERM /Through Tuesday Night/...
Issued 221 PM MDT SUN SEP 20 2026
Broad upper ridging will keep warm and dry conditions over the
region on Monday. Temperatures will warm several degrees from
today`s highs, reaching 5-10 degrees above normal. An eastward
shift in the ridge axis on Tuesday will allow for a closed low
to lift northeastward through the Great Basin. This will bring a
20-30% chance of showers and thunderstorms to higher terrain
along the northern NV border, the w-central Idaho mtns east of
McCall- Lowman- Prairie and the mtns in Baker County Tuesday
afternoon. Potential inhibiting factors for development would
be daytime cloud cover and eastern track of the low/dynamic
center. Temperatures are mostly unchanged on Tuesday with a few
degrees of cooling anticipated across w-central Idaho zones.

&&

.LONG TERM /Wednesday through Sunday/...
Issued 221 PM MDT SUN SEP 20 2026
A ridge will remain over the area through Friday with above
normal temperatures. A trough moves into the Pacific NW sometime
on Friday or Saturday with cooler temperatures and increased
chances (15 to 25 percent) of precipitation next weekend.
Precipitation chances will be highest north of Burns OR to
McCall ID, with generally dry conditions near the NV border.
Temperatures around 10 degrees above normal Wednesday and
Thursday, before falling to near normal on Friday, and 5 to 10
degrees below normal on Saturday and Sunday.

&&

.AVIATION /06Z Monday through Tuesday/...
Issued 957 PM MDT SUN SEP 20 2026
VFR. Patchy mountain valley fog overnight through Monday
morning, mainly near KMYL. Surface winds:
mainly variable or S-SE 5-10kt overnight through morning, then
E-SE 5-15 kt in the afternoon. Winds aloft at 10kft MSL:
variable 5-15kt.

KBOI...VFR with clear skies. Surface winds: SE 5-10kt overnight
through morning.

&&

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

OR...None.

&&

$$

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AVIATION.....JY
SHORT TERM...DG
LONG TERM....KA