355
FXUS65 KBOI 152008
AFDBOI

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

.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/...
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/...
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 /18Z Saturday through Sunday/...
Issued 1148 AM MDT SAT AUG 15 2026

Generally VFR. Increasing coverage of scattered showers and
thunderstorms across far E Oregon and SW Idaho by late morning
and afternoon. Storms capable of small hail, erratic outflows up
to 45 kt, and MVFR/IFR downpours. Surface winds outside of
storms: generally SE-SW 5-15 kt, with areas of gusts to 20-25
kt. Winds aloft at 10kft MSL: SW-S 5-20 kt.

KBOI...VFR. Isolated to scattered showers/thunderstorms
developing in SW Idaho this afternoon, with a 25 to 40% chance
of hitting KBOI terminal. Storms capable of 30-45 kt outflow
gusts and brief downpours. Surface winds: SE 5-15 kt, with gusts
to 15-25 kt this morning and early afternoon. Transitioning to
erratic/variable during late afternoon and evening due to nearby
storm activity.

Sunday Outlook...Showers and thunderstorms largely taper off
Sunday, with isolated coverage across central and south-central
ID. Surface winds: SW-NW 5-10 kt Sunday. Periods 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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SHORT TERM...JDS
LONG TERM....CH
AVIATION.....CH