466
FXUS65 KBOI 121038
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
438 AM MDT Wed Aug 12 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- A 15 to 20 percent chance of thunderstorms near the
  Idaho/Nevada border this afternoon.

- Showers and thunderstorms increasing in coverage Thursday,
  continuing through Saturday.

- Fire weather concerns increase due to threat of thunderstorms
  Thursday afternoon through Friday.

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

&&

.SHORT TERM /Through Friday Night/...
Issued 249 AM MDT WED AUG 12 2026
Today will be the last day of warm and dry conditions before a
pattern change come Thursday; barring a slight chance of showers
and thunderstorms (15-25% chance) in far southern Twin Falls
county this afternoon. High temperatures this afternoon will
rise to generally 85-95 degrees across lower elevations and the
high desert. Come Thursday, troughing over the Pacific
Northwest, aided by an ejecting shortwave, will offer increasing
chances of showers and thunderstorms. The aforementioned
shortwave is progged to cross over the eastern portion of our
CWA, giving way to the best chances of precipitation (30-50%)
falling near the ID/NV border and Central ID Mountains come
Thursday afternoon/evening. Weak instability Thursday afternoon
(limited by increased cloud cover) will allow for a 15-25%
chance of thunderstorms in the same areas mentioned above. With
this being the initial push of monsoonal moisture, the boundary
layer will still be dry, allowing for gusty winds and lightning
to be the primary hazard with Thursday afternoon storms. The
drier nature of this initial wave is also leading to elevated
fire weather concerns. Scattered showers will continue through
Friday across SW Idaho and far eastern Oregon. Continued
moistening will allow for some weak elevated instability to
remain overnight Thursday, so some nocturnal thunder can`t be
ruled out.

The best chances of precipitation (at least across southwest
Idaho) will come Friday, with LREF mean PWAT values ranging
from the 85-95th percentile. As has been the trend, the ID/NV
border and central ID mountains will have the highest odds of
precip, with a 60-90% chance. With the atmosphere becoming more
saturated at this point, the main hazard will transition from
gusty winds into heavy rain. Recently burned areas and
steep/rocky terrain will be most susceptible flooding and debris
flows with any heavy rain that does occur. Also... temperatures
will be around 5 degrees below normal come Friday.

&&

.LONG TERM /Saturday through Wednesday/...
Issued 249 AM MDT WED AUG 12 2026
Scattered showers and isolated to scattered thunderstorms will
continue Saturday as another shortwave passes over in the flow
aloft. With PWATS remaining around the 90th percentile (as the LREF
mean sees it), the hazards mentioned in the short-term Friday will
also carry over into Saturday. A warming and drying trend will set
in to start the coming week as ridging builds into the intermountain
west. Isolated afternoon showers and thunderstorms (10-20%
chance) will persist across higher terrain into the start of the
week. By mid-week, A low approaching from the west will lead to
increasing precipitation chances and a cooling trend yet again.

&&

.AVIATION /12Z Wednesday through Thursday/...
Issued 438 AM MDT WED AUG 12 2026

Generally VFR with some periods of MVFR possible in wildfire
smoke. A 15-20% chance of showers and thunderstorms south of
KTWF this afternoon. High density altitude this afternoon due
to heat. Surface winds: Variable under 10 kt this morning.
Becoming W-NW 10-20 kt this afternoon. Winds aloft at 10kft MSL:
W-SW 5-15 kt.

KBOI...VFR with reduction in visibility due to wildfire smoke at
times. Foothills obscured by smoke.. High density altitude this
afternoon due to heat. Surface winds: light and variable
this morning, becoming NW 7-12 kt with gusts up to 18 kt in the
afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Quality Alert until 1 PM MDT this afternoon for IDZ011-012-
     014-015-029-033.
     Fire Weather Watch from Thursday afternoon through late
     Thursday night for IDZ400>403-420-421-423-424-426.
OR...Fire Weather Watch from Thursday afternoon through late
     Thursday night for ORZ672>674.
     Air Quality Alert until 11 AM PDT this morning for ORZ061.
&&

$$

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AVIATION.....NF
SHORT TERM...NF
LONG TERM....NF