textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Smoke impacts continue through the start of the week.

- Breezy afternoon winds through Tuesday.

- Gradual cooling this week.

- Increasing shower and thunder chances Wednesday and beyond.

SHORT TERM /Through Tuesday Night/

Issued 221 AM MDT SUN AUG 9 2026 The disturbance that crossed our area today will work to suppress the high pressure aloft that has been dominating the forecast, and allow for a slight cooling trend to kick off. With the area under more zonal flow today and Monday, mid-level monsoonal moisture will be shunted just to the south and east of our area. Some virga showers can't be ruled out come this morning/early afternoon (mainly south of Twin Falls), however any shower and thunderstorm development this the afternoon should remain just outside of our area of responsibility. With the Great Basin high pressure aloft weakening and shifting to be over the Four Corners region, temperatures will gradually cool to near normal come Tuesday. Breezy afternoon winds will persist through Tuesday along ridgetops and the typical windy areas the Snake Plain. In those areas, winds will generally gust to around 20 mph, except to around 25 mph along ridgetops and in the Camas Prairie. With fires continuing to burn, smoke impacts will likely persist through the period.

LONG TERM /Wednesday through Sunday/

Issued 221 AM MDT SUN AUG 9 2026 The gradual cooling trend will continue through the long-term period as the high pressure aloft over the Four Corners region continues to weaken. Temperatures will generally be near normal, perhaps even leaning below normal to end the week. Troughing will begin to deepen near the west coast through the start of the period, putting the area under southwest flow aloft. This will allow for monsoonal moisture to begin creeping north across our area again. Chances for showers and thunderstorms will increase near the ID/NV border as early as Wednesday, before expanding north with each passing day. By Thursday, ensemble mean PWAT values reach the 85-90th percentile in our southern zones. With those values encompassing our entire area come Saturday.

AVIATION /12Z Sunday through Monday/

Issued 429 AM MDT SUN AUG 9 2026

Wildfire smoke resulting in periods of MVFR visibility and mountain obscuration. High density altitude this afternoon due to heat. A very low (5%) chance of thunder along the ID/NV border this afternoon. Surface winds: Light and variable this morning, becoming W-NW 10-20 kt this afternoon. Winds aloft at 10kft MSL: W-SW 10-20 kt.

KBOI...MVFR visibility possible due to wildfire smoke. Periods of foothill obscuration. High density altitude this afternoon due to heat. Surface winds: SW 3-8 kt this morning, then NW 8-12 kt with gusts to around 18 kt this afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Quality Alert until 1 PM MDT Monday for IDZ011>015-028-029- 033. OR...Air Quality Alert until 1 PM MDT /noon PDT/ Monday for ORZ061>064.