textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated showers and thunderstorms along the Idaho/Nevada border today. - Areas of smoke in southeast Oregon, drifting into southwest Idaho through the week.

- Hot temperatures this week, hottest on Monday.

- Showers/thunderstorms increase through midweek with heavy rainfall possible especially on Wednesday.

SHORT TERM /Through Tuesday Night/

Issued 338 AM MDT SUN JUL 19 2026 Hot and mostly dry conditions are expected today as an upper level ridge remains centered over the central U.S. An upper level trough moving across southern Canada will keep the flow aloft southwesterly and will transport drier air into the region. However, a 20% chance of showers and thunderstorms will persist along the Idaho/Nevada border this afternoon with lower chances elsewhere. Highs today will be similar to yesterday, in the upper 90s to around 100 degrees in the lower valleys. Smoke from wildfires mainly in Oregon will persist across southeast Oregon and increase across southwest Idaho today. Winds will mostly be light from the northwest, locally breezy in the afternoon and evening.

On Monday, the ridge will begin to build north along the West Coast, allowing for a return of southerly flow aloft. Monsoonal moisture will reenter the area, and a weak impulse early Monday will generate a 10-20% chance of showers across southeast Oregon and the west-central Idaho mountains. Temperatures will reach their peak on Monday before deeper moisture returns, with highs up to 103 degrees in the Treasure Valley. A Heat Advisory has been issued for portions of southwest Idaho and southeast Oregon. Warm overnight lows in the upper 60s to lower 70s at lower elevations will limit overnight relief. Shower and thunderstorm chances will rise to 20-40% near the Idaho/Nevada border in the afternoon/evening. Northwest winds will become breezy late in the day with wind gusts 15-30 mph. On Tuesday, increasing moisture will cool temperatures a couple degrees, but it will still be hot. Shower and thunderstorm chances will increase across the higher terrain but remain limited over the lower elevations. Storms will be capable of gusty winds and brief heavy rain. Smoke will persist across the area Monday and Tuesday.

LONG TERM /Wednesday through Sunday/

Issued 338 AM MDT SUN JUL 19 2026 Shower and thunderstorm potential will increase on Wednesday as an embedded shortwave trough lifts north through the Great Basin. This feature should provide additional lift for more widespread convection with a 20-60% chance of showers/storms across all areas. Deep monsoonal moisture in place (PW around 1.25 inches / above the 95th percentile) will create a risk of heavy rain and flash flooding, especially over burn scars and steep terrain. Starting Thursday, the flow aloft will turn southwesterly as an upper trough deepens off the Pacific Northwest coast. This will gradually push deeper moisture to the east with a drying trend from the west through the end of the week. By the weekend, only minimal chances for precipitation will persist across eastern areas. Southwest flow will bring hot, dry, and breezy conditions late week into the weekend. Smoke will likely continue to impact much of the area through the end of the week, especially across southeast Oregon.

AVIATION /12Z Sunday through Monday/

Issued 622 AM MDT SUN JUL 19 2026 Mainly VFR. Wildfire smoke across the area will locally reduce visibility to MVFR/IFR, especially near KBNO. Some improvement expected in the afternoon. High density altitude this afternoon due to heat. Isolated thunderstorms along the ID/NV border this afternoon. Isolated showers/virga lifting north through SE Oregon overnight. Surface winds: SW-NW 5-15 kt. Winds aloft at 10kft MSL: SW 5-15 kt.

KBOI...VFR. Visibility reduced due to wildfire smoke, although VFR expected to prevail. High density altitude this afternoon due to heat. Surface winds: light and variable this morning. Then NW 7-12 kt with occasional gusts to 20 kt this afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory from noon to 9 PM MDT Monday for IDZ012-014>016- 030-033. OR...Heat Advisory from noon MDT /11 AM PDT/ to 9 PM MDT /8 PM PDT/ Monday for ORZ063-064. Air Quality Alert until noon PDT Monday for ORZ061-062.