806
FXUS65 KBOI 152334
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
534 PM MDT Sat Aug 15 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Fire weather risk continues due to thunderstorm activity today.

- Thunderstorms could bring outflow winds up to 50 mph. In
  addition, heavy rain may also increase the risk for flash
  flooding, especially for vulnerable burn scars today.

- Temperatures near normal through Tuesday, then a few degrees
  of warming expected by late week.

&&

.SHORT TERM /Through Monday Night/...
Issued 208 PM MDT SAT AUG 15 2026
Strong thunderstorms are continuing to develop across the area
bringing heavy rain, small hail and gusty outflow winds to 50
mph. Despite the storms producing rainfall, lightning fire
starts are still a risk especially across the lower terrain.
High confidence (40% chance) in thunderstorms moving through the
Treasure Valley between 3 PM and 6 PM bringing brief heavy
rain, lightning and wind gusts up to 50 mph. Increased risk for
flash flooding on the recent burn scars especially the Wapiti
remains elevated through this evening. Please monitor the latest
weather information if you live or are traveling near the large
burn scars.

Convective activity will taper off late tonight as diurnal
cooling takes over and the primary shortwave exits to the
northeast. On Sunday, an upper level ridge builds over the Great
Basin, initiating an overall drying and warming trend. Moisture
will be significantly limited compared to Saturday, though
leftover instability will keep a slight chance (15 to 25
percent) of afternoon showers and thunderstorms over the higher
terrain of central and south-central Idaho. High temperatures on
Sunday will rebound to around 2 to 5 degrees above normal
across the lower valleys.

By Monday, residual monsoonal moisture around the western
periphery of the ridge will lead to an increase in mid-level
cloud cover and an expanding threat of afternoon and evening
showers and thunderstorms. The best coverage on Monday will be
focused over the higher terrain of northeast Oregon and
central/south-central Idaho, though isolated storms cannot be
ruled out for lower elevation valleys. Gusty erratic winds and
localized heavy downpours will once again be the main threats
with storm development on Monday. Temperatures Monday night will
remain mild, staying in the upper 50s and 60s for low
elevations.

&&

.LONG TERM /Tuesday through Saturday/...
Issued 208 PM MDT SAT AUG 15 2026
An upper-level shortwave trough will continue to move east through
the Pacific Northwest and Northern Rockies Tuesday and early
Wednesday. Shower and thunderstorm chances will be limited to the
higher terrain of central Idaho as this passes through. This
disturbance will suppress the upper-level ridge building in the
Great Basin on these days, however Wednesday afternoon onward the
ridge will amplify over the area. As the Desert Southwest ridge
builds, southwesterly flow aloft will overspread the region,
increasing temperatures and moisture gradually late week.
Additionally, models agree on a Pacific low pressure system slowly
moving onshore late week going into the weekend. This pattern will
support the influx of monsoonal moisture once again, with shower and
thunderstorm chances increasing by Friday and further Saturday.

&&

.AVIATION /00Z Sunday through Monday/...
Issued 528 PM MDT SAT AUG 15 2026
Scattered showers and thunderstorms through the late evening,
especially north and east of the Snake Plain and through the
Magic Valley of Idaho. Heavy rainfall, small hail, and wind
gusts to 40-45 mph with the strongest storms. Brief reductions
in visibility in blowing dust possible as well this evening.
Surface winds variable around 10 kt, except vrb 30g40 kt near
thunderstorms. Light diurnal winds overnight, favoring an ESE
direction. Winds aloft at 10kft: SW 10-20 kt.

KBOI...Showers moving to the northeast of the terminal by 01Z,
with lingering gust front winds around 20-25 kt. Drying with
diurnal SE winds developing this evening less than 10 kt.

Sunday Outlook...VFR area-wide with isolated
showers/thunderstorms across central/south-central Idaho in the
afternoon and evening. Brief MVFR/IFR possible along with gusty
winds near thunderstorms. Winds less than 10 kt elsewhere, along
with areas of smoke near KBKE/KBNO.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 9 PM MDT this evening for IDZ400-420-
     423-424-426.
     Flash Flood Watch until 9 PM MDT this evening for IDZ013.
OR...Red Flag Warning until 9 PM MDT /8 PM PDT/ this evening for
     ORZ672>675.
&&

$$

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AVIATION.....MC
SHORT TERM...JDS
LONG TERM....CH