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 Saturday Night/

Issued 213 PM MDT THU JUL 30 2026 Southwest flow aloft continues across the region between a broad upper high over the Four Corners and an approaching trough along the Pacific Northwest coast. Very warm and dry conditions will persist through Saturday. Wildfire smoke from several large fires across Oregon will remain through the weekend. This smoke will continue to degrade 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. Valley highs on Friday and Saturday will still reach into the mid to upper 90s.

The main forecast focus is a 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.

LONG TERM /Sunday through Thursday/

Issued 213 PM MDT THU JUL 30 2026 The cold front continues east across southwest Idaho on Sunday. Strong pressure gradients and tight thermal packing behind the front will maintain gusty northwest winds across the area through Sunday afternoon and evening. Gusts of 30 to 40 mph remain possible across higher terrain and along the Snake River Plain. Westerly winds will continue to transport wildfire smoke across the region, keeping degraded air quality in place through the end of the weekend. High temperatures on Sunday will drop 5 to 10 degrees behind the front, holding in the mid 80s to low 90s in the valleys.

From Monday through Thursday night, an upper-level trough over western Canada will keep the ridge over the Great Basin and Intermountain West largely suppressed, resulting in more westerly flow aloft. This may prevent smoke from the Big Grass fire from reaching the Treasure Valley, but 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. 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. With limited moisture return, precipitation chances remain near zero across southeast Oregon and southwest Idaho through Thursday night.

AVIATION /00Z Friday through Saturday/

Issued 557 PM MDT THU JUL 30 2026 Widespread wildfire smoke reducing visibilities with areas of MVFR and IFR conditions. Surface winds: SW-NW 5-12 kt through this evening. Gusty valley winds 10-15 kt with gusts 20-25 kt over KBKE and KONO in the evening, subsiding after midnight. Winds aloft at 10kft MSL: SW 5-15kt.

KBOI...Smoke reducing visibility. Surface winds: NW 5-10 kt, shifting to SE 5-10kt after sunset.

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. 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 Friday 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/ Friday for ORZ062>064.