textproduct: Boise

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.