031
FXUS65 KBOI 311120
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
520 AM MDT Fri Jul 31 2026

.UPDATE...Updated aviation discussion.

&&

.KEY MESSAGES...
- Wildfire smoke will persist across southeast Oregon and
  southwest Idaho through the weekend, keeping air quality
  degraded and hazy skies.

- A dry cold front will push through Saturday afternoon through
  Sunday, bringing gusty winds, cooler temperatures, and
  critical fire weather conditions.

&&

.SHORT TERM /Through Sunday Night/...
Issued 401 AM MDT FRI JUL 31 2026
Upper-level water vapor imagery this morning shows the upper-
level low offshore west of British Columbia. This low pressure
system (and associated upper-level trough) will very slowly
move onshore today and tomorrow, creating critical fire weather
conditions for our region Saturday and Sunday as a dry cold
front moves through.

Continued southwest flow aloft will persist over the region as
the Desert Southwest ridge remains in place with the trough
moving onshore. Very warm and dry conditions will persist
through Saturday. The main forecast focus is the dry cold
frontal passage arriving Saturday afternoon. As the front
approaches, southwest to west winds will increase Saturday
morning, turning gusty from the west-northwest Saturday
afternoon and evening behind the boundary. Wind gusts of 25 to
35 mph are expected in exposed valley locations, high terrain,
and wind-prone corridors like the Baker Valley. Combined with
afternoon relative humidity dropping into the single digits and
low teens, the gusty winds will lead to critical fire weather
conditions across much of the area Saturday afternoon through
Saturday night. On Sunday, temperatures are forecast to be 5-10
degrees below normal, with most areas seeing temperatures
decrease by 5-10 degrees compared to Saturday. Winds will
remain gusty on Sunday as the front continues southeast through
the Great Basin, continuing elevated fire weather concerns in
Southwest Idaho.

Wildfire smoke will continue to linger in the
area, degrading air quality while keeping daytime high
temperatures a few degrees lower than full solar heating would
allow. There could be some near-surface improvement in smoke
concentrations with the cold frontal passage Saturday afternoon
and evening as it promotes deeper boundary layer mixing.

&&

.LONG TERM /Monday through Friday/...
Issued 401 AM MDT FRI JUL 31 2026
Continued upper-level troughing over southern Canada is expected
to temper the Desert Southwest ridge from building too far into
the region. This will result in weak westerly flow aloft. A steady drying
trend will continue, with lower elevation temperatures returning
to the mid 90s by Wednesday and Thursday. Winds will subside
compared to the weekend, returning to typical afternoon breezy
conditions. Additionally, PWAT values will drop under the 10th
percentile climatology across the region, with values near 0.3
inches Monday through Thursday. This will cause precipitation
chances to remain near zero across southeast Oregon and
southwest Idaho. Several large fires across eastern Oregon will
continue to spread smoke across western Idaho, thus, smoky
conditions are likely to persist through the end of the week.

&&

.AVIATION /12Z Friday through Saturday/...
Issued 520 AM MDT FRI JUL 31 2026

Widespread wildfire smoke reducing visibilities, with areas of
MVFR and IFR conditions. High density altitude this afternoon.
Surface winds: variable under 12 kts. Winds aloft at 10kft MSL:
S 5-15 kt.

KBOI...Smoke reducing visibility, clearing by afternoon. High
density altitude this afternoon. Surface winds: variable 4-8
kt.

Weekend Outlook...Smoke reducing visibility. Dry frontal
passage on Saturday will bring gusty NW winds over all areas
Saturday afternoon/evening and mainly east of KBOI Sunday
afternoon. This could improve the dense smoke coverage for some
areas. High density altitude Saturday. Surface winds: SW-NW
10-20 kt with gusts 20-30 kt Saturday/Sunday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Quality Alert until 2 PM MDT this afternoon for IDZ011>015-
     028-029-033.
     Fire Weather Watch from Saturday afternoon through Saturday
     evening for IDZ402-423.
OR...Fire Weather Watch from Saturday afternoon through Saturday
     evening for ORZ670>675.
     Air Quality Alert until 1 PM MDT /noon PDT/ this afternoon for
     ORZ062>064.
&&

$$

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AVIATION.....CH
SHORT TERM...CH
LONG TERM....CH