textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Showers/thunderstorms today, mainly across south-central Idaho and the central Idaho mountains. Storms will be capable of heavy rainfall with a limited flash flood risk, gusty outflow winds to 60 mph, and small hail.

- Areas of smoke across southeast Oregon today through the weekend, possibly expanding into southwest Idaho at times.

- Hot temperatures continue into next week, with valley highs in the upper 90s to around 100 degrees.

- Showers/thunderstorms decrease this weekend, then increase next week with heavy rainfall possible.

SHORT TERM /Through Sunday Night/

Issued 347 AM MDT FRI JUL 17 2026 An upper level low along the coast of Washington and an upper level ridge to our east will result in southerly flow aloft across the area. While drier air will move into southeast Oregon, monsoonal moisture will increase across Idaho today, especially south-central Idaho into the central Idaho mountains where precipitable water will climb to the 95th-99th percentile. Isolated showers and thunderstorms will develop along a weak disturbance this morning across far eastern Oregon and west- central Idaho. This afternoon, aided by daytime heating, shower and thunderstorm coverage will increase across the central Idaho mountains and south-central Idaho. Thunderstorms will be capable of heavy rainfall, resulting in a localized threat of flash flooding, with the biggest risk over burn scars and steep terrain. A Flash Flood Watch remains in effect for the Wapiti burn area this afternoon and evening. Thunderstorms will also be capable of gusts 30-50 mph with isolated up to 60 mph and small hail.

Thunderstorms will lift northeast out of the area this evening. On Saturday, the flow aloft will become southwesterly, and by Sunday nearly westerly as the upper low along the Washington coast moves across southwest Canada. This will push monsoonal moisture to the east, decreasing shower and thunderstorm chances Saturday and limiting coverage to the easternmost zones. By Sunday, coverage will be limited to the higher terrain across south-central Idaho.

Temperatures will remain hot through the period, with lower valley highs in the upper 90s to around 100 degrees. Winds outside of thunderstorms will be typical with afternoon breezes developing. Finally, smoke from fires primarily in central Oregon has moved into southeast Oregon, with impacts likely to continue through the weekend, especially at night. Smoke may also push into southwest Idaho over the weekend, although confidence is lower.

LONG TERM /Monday through Friday/

Issued 347 AM MDT FRI JUL 17 2026 As the upper trough over Canada moves east, the upper ridge centered over the central U.S. will expand to the west and strengthen. This will allow the flow aloft to become southerly, transporting monsoonal moisture into the area once again. Chances for showers and thunderstorms will initially be focused across southern Idaho on Monday, with a greater than 15% chance of showers/storms expanding across the higher terrain on Tuesday. Moisture will continue to surge into the area Wednesday and Thursday, with ensemble-mean precipitable water once again rising above the 95th percentile. This will bring a 30-60% chance of showers and thunderstorms to all areas both days. Development may be aided by shortwave impulses as hinted at by deterministic models. Shower/storm chances decrease slightly on Friday. Due to the very moist airmass, heavy rain will be a concern and any flash flood threats will be closely monitored through the week. Despite the moisture, temperatures will remain hot through the period, generally a few degrees above normal thanks to the ridge over the area.

AVIATION /12Z Friday through Saturday/

Issued 550 AM MDT FRI JUL 17 2026 Mainly VFR. Isolated showers/thunderstorms this morning near the ID/OR border. Isolated to scattered/numerous showers and thunderstorms this afternoon, mainly over south-central/central ID. Localized MVFR/IFR and mountain obscuration in thunderstorms. Outflow gusts 30-50 kt from storms possible. High density altitude due to heat in the afternoon. Areas of smoke in SE Oregon reducing visibility, especially near KBNO. Surface winds outside of storms: SE-SW 5-15 kt, becoming variable this evening. Winds aloft at 10kft MSL: S 10-20 kt.

KBOI...Mainly VFR. A 30% chance of thunderstorms over the terminal this morning, and again this afternoon after 21Z. Thunderstorms capable of gusts to 30 kt and brief heavy rain. High density altitude due to heat this afternoon. Surface winds: W-NW 5-10 kt.

Weekend Outlook...Mainly VFR. Chance of showers/thunderstorms over south-central ID and the central ID mtns Saturday afternoon, then limited to south-central ID Sunday afternoon. Mountain obscuration from storms. High density altitude due to heat. Surface winds outside of storms: SW-NW 5-15 kt, afternoon gusts 15-25 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID... Flash Flood Watch from 1 PM MDT this afternoon through this evening for IDZ013. OR...None.