944
FXUS65 KBOI 181721
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1121 AM MDT Tue Aug 18 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Temperatures warming through the end of the week with lower
  elevations around 100 degrees Thursday and Friday.

- Increased chance of showers and thunderstorms over higher
  terrain this weekend and into next week.

&&

.SHORT TERM /Through Thursday Night/...
Issued 418 AM MDT TUE AUG 18 2026
An amplifying Four Corners ridge will turn up the heat across
the region through Thursday. Today a weak wave passing to the
north and the lingering of mid-level moisture will feed
afternoon cumulus development across higher terrain of SW Idaho.
A few of the cu will see enough growth to drop light rain and
maybe a rumble of thunder in the w-central ID mtns north and
east of McCall and along the ID/NV border south of Twin Falls.
The heat will continue to build Wednesday and Thursday with
temperatures pushing to around 100 across lower elevations.
Wednesday is dry across the board. Increasing mid-level moisture
on Thursday will support a 5-10% chance of thunder south of
Twin Falls. Would expect gusty winds and little rain from any
cells that develop.

&&

.LONG TERM /Friday through Tuesday/...
Issued 418 AM MDT TUE AUG 18 2026
The upper ridge will hold through Friday bringing another day
of 100 degree heat to lower elevations. A trough lingering off
the West Coast will push inland late Friday, moving through the
Interior NW on Saturday. Cooling aloft and increased moisture
will support a 20-30% chance of showers and thunderstorms across
higher terrain of e-central Oregon and SW Idaho Friday,
shifting to mostly SW Idaho for Saturday and Sunday. Given
precipitable water content in the 70-75th percentile, wouldn`t
be surprised to see the coverage and probability of
showers/storms increase some as we get closer to the weekend.
Clouds and cooling aloft will help bring temperatures back to
near normal over the weekend. Models show the upper ridge
rebounding early next week as the trough exits to the east. This
will likely bring a return of above normal temperatures.
Southeast Oregon remains dry into early next week while the
western edge of monsoon moisture keeps a 10-30% chance of
showers/storms over SW Idaho.

&&

.AVIATION /18Z Tuesday through Wednesday/...
Issued 1120 AM MDT TUE AUG 18 2026

VFR with mid-high clouds across far SE Oregon and southern Idaho.
Scattered afternoon cumulus in mtns with isolated
showers/thunderstorms north and east of KMYL and higher terrain
south of KTWF. Surface winds: W-NW 5-15 kt. Winds aloft at 10kft
MSL: W-SW 5-15 kt, becoming W 5-20 kt by 00z/Wed.

KBOI...VFR with scattered high clouds through this morning.
Light surface winds with variable direction becoming NW in the
afternoon.

&&

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

OR...None.

&&

$$

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AVIATION.....CH
SHORT TERM...DG
LONG TERM....DG