textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Heat Advisory through Monday evening for south-central Idaho. - Showers and thunderstorms return Monday evening through the week, with peak coverage on Tuesday.

- Tuesday storms will be capable of heavy downpours and gusty outflows, potentially affecting steep terrain and burn scars.

- Hot temperatures remain through the week.

SHORT TERM /Through Tuesday Night/

Issued 309 AM MDT SUN JUL 12 2026 A few degrees of cooling is anticipated today, as strong high pressure shifts slightly eastward and cloud cover thickens from monsoon moisture. This moisture will remain at mid/upper levels, while lower levels remaining hot and dry...with max temperatures around 5-10 degrees above normal. As a result, widespread virga is anticipated today, with a 10% chance of light rain/sprinkles making it to the surface in E Oregon. Winds will gust to 20-35 mph this afternoon, with highest gusts in portions of E Oregon. Hot temperatures and mid-level moisture will continue into Monday and eventually produce isolated to scattered rain showers by Monday evening. Lightning chances are currently low Monday due to weak instability parameters, and any lightning produced will be limited to SE Oregon and higher terrain of SW Idaho. Activity will be capable of gusty outflow winds, however, as the drier low-levels combine with steep lapse rates from daytime heating/mixing.

The influx of monsoon moisture will then continue into Tuesday. Lower levels will start to moisten, with shower/thunderstorm chances increasing area-wide throughout the day. Precipitable water values will peak Tuesday with models averaging well over 1.00". Therefore, conditions will be favorable for heavy downpours, elevating concerns for areas with steep terrain and newer burn scars. Rain-induced cold-pools will also be a concern, promoting gusty outflow winds through Tuesday night.

LONG TERM /Wednesday through Sunday/

Issued 309 AM MDT SUN JUL 12 2026 A Pacific trough will begin to move inland by mid week, nudging the bulk of the monsoon moisture toward the east. Hot surface temperatures and continued moist mid-levels will keep shower and thunderstorm chances for the higher terrain Wednesday and Thursday, mainly over SW Idaho mountains. Models start to mishandle the propagation of the Pacific trough and moisture Friday into the weekend, leading to low forecast confidence of showers/thunderstorms within the forecast area. Overall, slight chances linger over higher terrain as hot, south-southwest flow attempts to dominate through the weekend. Surface max temperatures should remain 5-10 degrees above normal through the forecast period.

AVIATION /12Z Sunday through Monday/

Issued 525 AM MDT SUN JUL 12 2026

VFR. Increasing high clouds/virga, and a 10% chance of light rain in E Oregon this PM. Areas of reduced visibility from wildfire smoke/haze, especially near KBKE. High density altitude due to heat. Surface winds: variable up to 12 kt, then SW-NW 5-15 kt this afternoon, and gusts to 20-30 kt for portions of E Oregon and Snake Plain. Winds aloft at 10kft MSL: S-SW 15-30 kt.

KBOI...VFR and high clouds/virga. Visibility reduced at times by wildfire smoke in foothills NE of KBOI. High density altitude due to heat. Surface winds: W to NW 5-15 kt. Occasional afternoon gusts around 20 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory until 9 PM MDT Monday for IDZ016-030. OR...None.