245
FXUS65 KBOI 170614
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1214 AM MDT Mon Aug 17 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Isolated showers and thunderstorms today and Monday favoring
  higher terrain, with outflows up to 40 mph and local downpours.

- Temperatures near or slightly above normal through mid-week,
  then further warming expected by late week.

- Return of monsoon moisture Friday into the weekend will
  increase shower and thunderstorm chances once again.

&&

.SHORT TERM /Through Wednesday Night/...
Issued 208 PM MDT SUN AUG 16 2026
An upper level ridge centered over the Intermountain West will
maintain warmer and drier conditions across southeast Oregon and
southwest Idaho through the short term period under
southwesterly flow aloft. Mid-level moisture streaming around
the western periphery of this ridge will interact with weak
instability today, generating isolated afternoon and evening
thunderstorms. The highest confidence for storm development
today remains focused over the higher terrain of southwest
Idaho, including the Owyhee Mountains and West Central
Mountains. With low levels remaining quite dry, main threats
with today`s storms will be localized gusty outflow winds up to
45 mph and brief dry lightning strikes.

A weak shortwave trough is shown to move inland across the
forecast area on Monday bringing mid-level Pacific moisture.
Although this moisture is not as extensive as the monsoonal
moisture from the previous couple of days, the incoming dynamic
support, combined with daytime heating, should be sufficient to
support isolated thunderstorm development across the area Monday
afternoon and evening. Given the limited low-level moisture,
storms are likely to produce gusty outflow winds 35 to 45 mph,
along with frequent lightning and little to no rainfall
increasing the risk for further fire starts.

Another trough passage on Tuesday should briefly suppress the
ridge for slightly cooler temperatures, though still above
normal and breezy conditions. Cooler air aloft and lingering
mid-level moisture will maintain a slight chance of afternoon
mountain thunderstorms, mainly over the Central Idaho Mountains,
but overall coverage will decrease compared to Monday.
Temperatures throughout the short term will remain roughly 5
degrees above seasonal averages.

&&

.LONG TERM /Thursday through Monday/...
Issued 208 PM MDT SUN AUG 16 2026
As the Desert Southwest upper-level ridge builds Wednesday,
temperatures will be near normal under dry conditions. Starting
Thursday, flow aloft will be shifting from southwesterly to
southerly as a Pacific low pressure system moves closer to shore.
This will increase precipitation chances Thursday and further
Friday, primarily over higher terrain. Temperatures will become hot
Thursday and Friday under this pattern. Late Friday into the
weekend, the trough will move onshore and then northeast across the
Pacific Northwest states. Showers and thunderstorm chances will
persevere as the trough enhances large-scale lift and carries
moisture. Several degrees of cooling will be likely for Saturday and
Sunday.

&&

.AVIATION /06Z Monday through Tuesday/...
Issued 1201 AM MDT MON AUG 17 2026

Generally VFR. Isolated showers and thunderstorms developing this
afternoon across SW Idaho and far E Oregon, especially around
KTWF/KJER. Erratic outflows around 30 kt possible. Patchy
surface smoke near KBKE/KBNO. Surface winds: variable up to 10
kt, becoming SW-NW 5-15 kt this afternoon. Winds aloft at 10kft
MSL: SW 5-15 kt.

KBOI...VFR. Isolated showers/thunderstorms in SW Idaho Monday
evening, with a 10% chance of hitting KBOI. Possible storm
outflows to around 30 kt in Treasure Valley. Surface winds: SE
4-8 kt, shifting to NW 5-10 kt in the afternoon.

&&

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

OR...None.

&&

$$

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AVIATION.....SH
SHORT TERM...JDS
LONG TERM....CH