750
FXUS65 KBOI 132335
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
535 PM MDT Thu Aug 13 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Fire weather concerns increase due to threat of thunderstorms
  this afternoon into Friday.

- Thunderstorms with heavy rain may also increase the risk for
  flash flooding especially for recent burn scars on Friday and
  Saturday.

- Temperatures cooling to around 5 degrees below normal come
  Friday.

&&

.SHORT TERM /Through Saturday Night/...
Issued 235 PM MDT THU AUG 13 2026
An active convective pattern is taking shape across southeast
Oregon and southwest Idaho as monsoonal moisture continues to
flow northward. An embedded shortwave over the northern Great
Basin will move northeast through late this evening, providing
dynamic lift to trigger scattered showers and thunderstorms
across southern Idaho. Further west, increasing moisture along
an approaching upper level trough combined with afternoon
destabilization will initiate thunderstorms across much of
southeast Oregon after 20Z.

Convective activity tonight, especially across southeast
Oregon, will initially maintain a dry posture due to low-level
sub-cloud dry air. Strong, localized outflow wind gusts up to 45
mph and frequent lightning are the primary threats with
tonight`s storms. Given receptive fuels and dry lightning
potential, fire weather risks remain elevated across eastern
Oregon and southwest Idaho. Light precipitation is possible with
showers and thunderstorms this evening along and just north of
the Nevada border.

The threat for thunderstorms will continue overnight before a
brief break late Friday morning. By Friday afternoon, deep
monsoonal moisture fully encompasses southwest Idaho.
Precipitable water (PWAT) values will climb toward the 80th to
95th percentile, with the strongest moisture advection and
dynamic forcing focused over central Idaho. As the atmospheric
column saturates, the main hazard will transition from dry
lightning and gusty winds to localized heavy rain. The risk for
flash flooding and debris flows will increase noticeably Friday
afternoon and evening, particularly over steep terrain and
recent burn scars such as the Wapiti burn scar. A Flash Flood
Watch has been issued for the Wapiti Burn Area. Burn scars from
the Claremont Fire, Big Grass Fire, Tartar Fire, Fox Fire, and
Colman Creek Fire all have an elevated risk for flash flooding
through Saturday and will be monitored.

A secondary shortwave will traverse the region on Saturday,
keeping elevated PWATs and scattered thunderstorm chances in
place over southwest Idaho. The threat for localized flash
flooding over vulnerable burn scars will persist through
Saturday afternoon. Increased cloud cover and precipitation will
maintain high temperatures around 5 degrees below seasonal
averages through Saturday.

&&

.LONG TERM /Sunday through Thursday/...
Issued 235 PM MDT THU AUG 13 2026
A ridge of high pressure will build back into the region on Sunday,
bringing warm and mostly dry conditions to the area. Lingering
moisture aloft will keep a slight chance of showers and
thunderstorms over high terrain in the central Idaho mountains. A
quick moving trough will bring cooler air with increased chances of
showers and thunderstorms on Tuesday into early Wednesday.
Confidence in the forecast after Wednesday decreases thanks to
increased model variability. Significant disagreement exists in the
long term, with some model solutions showing a trough through the
northwest towards the end of the week while other models depict a
ridge of high pressure building back in over the Intermountain West
through the end of the week. If the trough slows over our region,
cooler and wetter conditions will occur, but expect very hot and dry
and conditions if the ridge builds quickly back into the area.
Current forecasts favor the ridge building quickly back in, with a
higher probability of warm and dry conditions continuing through the
end of the week.

&&

.AVIATION /00Z Friday through Saturday/...
Issued 532 PM MDT THU AUG 13 2026
Isolated to scattered showers and thunderstorms across the area
through late this evening. Outflow gusts up to around 40 kt
near thunderstorms. Storms near KBKE and KMYL will continue
through the night, though lightning activity will subside.
Surface winds: SW-NW 5-15 kt. Variable and gusty winds to 25 kt
near showers. Becoming light and variable after sunset. Winds
aloft at 10kft MSL: W-SW 5-15 kt.

KBOI...VFR with reduction in visibility due to wildfire smoke.
Foothills obscured by smoke. A 20% chance of showers and
thunderstorms by late evening through early tomorrow morning.
Surface winds: SE 10-20 kt.

Weekend Outlook...Isolated to scattered showers and
thunderstorms continuing Saturday. Storms Saturday capable of
heavy rain, gusty outflows, and MVFR conditions. Showers taper
off come Sunday with clearing skies. Surface winds: SW-SE 5-15
kt Saturday, then SW-NW 5-10 kt Sunday. Light and variable
overnight.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Red Flag Warning until 6 AM MDT Friday for IDZ400>403-420-421.
     Red Flag Warning until 8 PM MDT Friday for IDZ423-424-426.
     Flash Flood Watch from Friday afternoon through Saturday
     evening for IDZ013.
OR...Red Flag Warning until 5 AM PDT Friday for ORZ670>672.
     Red Flag Warning until 8 PM MDT /7 PM PDT/ Friday for
     ORZ673>675.
     Air Quality Alert until 1 PM MDT /noon PDT/ Friday for ORZ061-
     063-064.
&&

$$

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AVIATION.....JM
SHORT TERM...JDS
LONG TERM....SA