textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Heat Advisory today and Saturday for lower elevations of southwest Idaho and southeast Oregon, but continuing through Monday evening in south-central Idaho.

- Breezy afternoon winds through the weekend. - Shower and thunderstorm chances return late Monday through Tuesday night with the arrival of monsoon moisture.

SHORT TERM /Through Sunday Night/

Issued 227 PM MDT FRI JUL 10 2026 We are maintaining the current Heat Advisory for the Treasure Valley, Upper Weiser River Valley, and southwest Idaho Highlands through Saturday evening, but extending it through Monday evening in the western Magic Valley and southern Twin Falls County. Those areas will remain closest to the main upper level high pressure dome centered over the northern Plains and covering half the US. Southwest flow aloft over the western US will draw monsoon moisture toward our CWA beginning Saturday, with increasing clouds in Oregon beginning Saturday night and in Idaho beginning Sunday, eventually leading to high-based thunderstorms in all southern zones Monday evening. The clouds will keep nighttime temps warm and provide only limited relief from the daytime heat. Afternoon winds will gust to 30 mph in Baker and Harney Counties, and up to 20 mph elsewhere.

LONG TERM /Monday through Friday/

Issued 227 PM MDT FRI JUL 10 2026 The upper-level ridge centered over the Northern Great Plains will be quite strong Monday and Tuesday, driving a monsoonal push of mid/high level moisture and precipitable water values northward into the region. As a result, shower and thunderstorm chances will increase starting late Monday, favoring higher terrain. Initial convection will lean drier and be outflow dominant from preceding dry low-levels, but should soon become heavier rain producers Tuesday into Wednesday as PWAT values reach 1.00"+ (i.e., above 95th percentile relative to climatology) and low- levels moisten. Shower/thunderstorm chances will expand to most areas by Tuesday. Concern will gradually shift from fire danger Monday and Tuesday (due to lightning on dry fuels), to flash- flood potential by Tuesday and Wednesday (especially over burn scars). Meanwhile, a broad Pacific trough is forecast to move southward along the West Coast Monday and Tuesday, but models disagree on when to bring the trough onshore and push monsoon moisture toward the east. The trough evolution will determine whether showers and thunderstorms continue through the rest of the week/next weekend, or gradually decrease around mid- week. Overall, southerly flow is expected to persist through Friday and support hot temperatures area-wide.

AVIATION /00Z Saturday through Sunday/

Issued 550 PM MDT FRI JUL 10 2026 VFR. Areas of reduced visibility from wildfire smoke. High density altitude due to heat this evening until sunset. Surface winds: SW- NW 10-15 kt with gusts to 20-30 kt over SE Oregon and higher terrain of SW Idaho this evening, lowering to S-SE or variable 5-15 kt tonight after sunset. Winds aloft at 10kft MSL: SW 5-15 kt.

KBOI...VFR. High density altitude due to heat this evening. Visibility reduced at times by wildfire smoke in foothills NE of KBOI. Surface winds: NW-N 5-10 kt, becoming SE 5-10 kt tonight after sunset.

Weekend Outlook...VFR. Areas of reduced visibility from wildfire smoke. High density altitude due to heat, especially Saturday. Surface winds: SW-NW 5-15 kt Sat/Sun. Afternoon gusts to 20-30 kt across SE Oregon and mainly the higher terrain of SW Idaho.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory until 9 PM MDT Saturday for IDZ012-014-015-033. Heat Advisory until 9 PM MDT Monday for IDZ016-030. OR...Heat Advisory until 9 PM MDT /8 PM PDT/ Saturday for ORZ064.