textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Chance of showers and thunderstorms mostly over higher terrain through Friday.

- Hot temperatures into the upcoming weekend with valley highs around 100 degrees.

SHORT TERM /Through Friday Night/

Issued 312 AM MDT WED JUL 15 2026 A weak shortwave trough and lingering monsoonal moisture are generating isolated thunderstorms over central Oregon and portions of southern Idaho early this morning. Localized wind gusts up to 40 mph have been associated with the thunderstorm cluster near the ID-NV border. Activity is expected to taper off by mid-morning as the shortwave exits to the northeast. Later today, a broad Pacific trough along the west coast will shift inland today, nudging the bulk of the monsoonal moisture toward the east. However, residual mid-level moisture and synoptic lift will trigger the next round of isolated showers and thunderstorms this afternoon across central/east Oregon and higher terrain of SW Idaho. Enhanced diurnal heating and drying low-levels will increase the potential for thunderstorm outflow wind gusts to 30-45 mph. Outside of storms, the clearer skies and drying conditions will encourage hotter afternoon temperatures compared to Tuesday.

On Thursday, the Pacific trough will track northeast into BC Canada, allowing the large high pressure dome over the central U.S. to re-build westward. This pattern shift will carry the monsoon moisture back west, resulting in more shower and thunderstorm activity across southwest Idaho both Thursday and Friday afternoons. Additionally, the building ridge will heat temperatures further, with lower elevations reaching or exceeding 100 degrees both days.

LONG TERM /Saturday through Wednesday/

Issued 312 AM MDT WED JUL 15 2026 Southwest flow aloft will dominate the long term pattern as prominent high pressure remains stationary over the the central U.S. This will maintain an influx of monsoonal moisture, resulting in continual rounds of afternoon showers and thunderstorms across southern/central Idaho and portions of E Oregon. Hot temperatures will persist at approximately 5-10 degrees above normal each afternoon. As a result, broad areas of moderate-level Heat Risk are expected for lower elevations and mountain valleys, affecting individuals sensitive to heat. Toward mid-week, a few model members attempt to flatten the ridge, which would transition the upper flow to more westerly and reduce temperatures/storm activity. However, forecast confidence remains low at this time.

AVIATION /12Z Wednesday through Thursday/

Issued 526 AM MDT WED JUL 15 2026

Generally VFR. Isolated showers/thunderstorms returning this afternoon, mainly over E Oregon and near the ID-NV border. Outflow gusts to 25-40 kt. Surface winds: variable 5-15 kt. Winds aloft at 10kft MSL: variable SW 5-15 kt.

KBOI...VFR. Surface winds: variable under 6 kt, becoming NW 6-12 kt with gusts up to 20 kt late morning/afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.