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 with Heat Advisories in the Snake Plain and high desert.

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

SHORT TERM /Through Tuesday Night/

Issued 159 PM MDT SUN JUL 19 2026 Hot and dry conditions as an upper level ridge remains in place. Southwesterly flow today is transporting a band of altocumulus with virga showers in it, but the overall chance of storms is low. Only a small portion of south-central Idaho in our area, south of the Magic Valley, will have isolated thunderstorms. These could produce gusty winds, lightning, and heavy rain, but will stay relegated to that small corner of our area. High temperatures remain hot with temperatures in the Snake Plain around 100 degrees. Some seasonally breezy winds across the area with gusts 15-25 mph.

On Monday, southerly flow aloft brings the return monsoonal moisture that evening, but not before the hottest day in our forecast. Heat Advisories have been issued with temperatures in the Snake Plain expected to be as high as 105 degrees with morning temperatures in the low 70s. 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 159 PM MDT SUN JUL 19 2026 Southerly flow aloft will remain over the area Wednesday, with the region between the upper-level ridge in the south-central U.S. and upper-level troughing off the Pacific NW coast. The greatest chances for showers and thunderstorms in the extended period will be on Wednesday, as an embedded shortwave trough lifts north through the Great Basin. This feature should provide additional lift for convection, with most areas seeing a 20-60% chance of showers/thunderstorms. Precipitable water values will still be hovering around the 95th percentile during this time, creating the 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 our eastern zones. 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 /00Z Monday through Tuesday/

Issued 559 PM MDT SUN JUL 19 2026

Mainly VFR. Wildfire smoke across the area will locally reduce visibility to MVFR/IFR, especially near KBNO. Some improvement this evening and Mon/PM. Isolated showers/virga lifting north through SE Oregon overnight. Afternoon high density altitude through the week. Surface winds: Generally variable up to 8 kt. Winds aloft at 10kft MSL: W-SW 5-15 kt.

KBOI...VFR. Visibility reduced due to wildfire smoke, although VFR expected to prevail. Afternoon high density altitude this week due to heat. Surface winds: NW 7-12 kt this evening becoming light and variable overnight.

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.