textproduct: Boise

KEY MESSAGES

- Isolated severe thunderstorms over south-central Idaho late this afternoon through early evening pose a threat for isolated strong outflow winds up to 60 mph.

- Smoke will limit high temperatures and continue degraded air quality through the end of the week.

- A dry cold frontal passage Saturday into Sunday will bring gusty winds and elevated fire weather concerns, with gusty conditions continuing into Sunday due to a tight surface pressure gradient.

SHORT TERM /Through Friday Night/

An upper level ridge centered over the Intermountain West will maintain hot and dry conditions across southeast Oregon and southwest Idaho through Friday night. High temperatures will be moderated due to the persistent smoke across much of the forecast area but should still reach above normal for many locations. Lower valley locations will range from the upper 90s to low 100s, accompanied by low relative humidity values during the peak heating hours.

Isolated severe thunderstorms are expected to develop late this afternoon into early this evening across south-central Idaho, particularly within southern Twin Falls County and the Western Magic Valley. There is sufficient middle level moisture and strong enough surface heating to yield elevated instability across south-central Idaho. Inverted-V thermodynamic profiles on forecast soundings highlight a favorable environment for isolated strong outflow winds up to 60 mph which has been outlined in SPC's marginal risk today.

LONG TERM /Saturday through Wednesday/

A pattern transition begins Saturday as an upper level trough moves across the Pacific Northwest and pushes a dry cold front through southeast Oregon and southwest Idaho Saturday afternoon into Sunday morning. Minimal atmospheric moisture will limit precipitation potential with this passage, keeping conditions predominantly dry across the area.

The primary impact from this frontal passage will be strong and gusty winds. West to northwest surface winds will increase to 20 to 30 mph with gusts up to 40 mph along and behind the front Saturday afternoon and evening. Combined with low relative humidity, these gusty winds will result in heightened fire weather concerns across the region. This wind threat will continue into Sunday across southwest Idaho with the tight surface pressure gradient behind the exiting front.

Behind the front, daytime temperatures will drop 5 to 10 degrees on Sunday and Monday, bringing high temperatures back down to near seasonal normals. High pressure will begin to rebuild over the Great Basin Tuesday into Wednesday, leading to lighter winds and a gradual warming trend through mid-week.

AVIATION /18Z Wednesday through Thursday/

Issued 1231 PM MDT WED JUL 29 2026 Widespread wildfire smoke reducing visibilities with MVFR to IFR conditions. Mountains obscured in smoke. Isolated thunderstorms SE of KTWF and KJER this afternoon with gusty winds up to 45kt in vicinity of storms. Surface winds: SW-NW 5-10 kt in the afternoon. Winds aloft at 10kft MSL: SW 5-15kt.

KBOI...MVFR conditions from wildfire smoke through early afternoon. Improvements in visibilities possibly later this afternoon and evening. Surface winds SE 4-7kt this morning, becoming NW 5-10 kt with gusts up to 17 kt in the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Quality Alert until 2 PM MDT Friday for IDZ011>015-028-029- 033. Red Flag Warning until 9 PM MDT this evening for IDZ426. Air Quality Alert until 1 PM MDT Thursday for IDZ016-030. OR...Air Quality Alert until 1 PM MDT /noon PDT/ Friday for ORZ062>064.