textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Warm and dry conditions will persist over the next several days.

- Smoky conditions will limit high temperatures by a few degrees and continue degraded air quality into the weekend.

- Breezy winds and cooler than normal temperatures Sunday into early next week.

SHORT TERM /Through Thursday Night/

Issued 318 AM MDT TUE JUL 28 2026 The large high pressure anchored over the Desert Southwest will continue southwesterly flow over our area through late week. A weak Pacific shortwave trough steering across the Great Basin through midweek will bring isolated thunderstorms over the lower Magic Valley near the NV border this afternoon and Wednesday afternoon. Otherwise, our area will stay very dry with light to moderate wind breezes. The southwesterly flow will continue to transport wildfire smoke from several large fires across southeast Oregon into southwest Idaho, resulting in persistent haze, degraded air quality, and reduced surface visibilities.

Smoke coverage will continue to limit daytime mixing and lower afternoon high temperatures by a few degrees through the week across lower valleys, keeping daytime highs near or slightly below seasonal normals. Nocturnal and early morning surface inversions, along with downvalley drainage winds, will keep smoke localized in valley floors, particularly in the Treasure Valley and Baker Valley corridors, before mild afternoon mixing offers brief, temporary visibility improvements.

LONG TERM /Friday through Tuesday/

Issued 318 AM MDT TUE JUL 28 2026 With troughing over British Columbia and high pressure aloft over the Four Corners region, hot, dry, and breezy conditions will continue through the end of the week. As such, the dense wildfire smoke coverage will likely not see improvements towards the weekend. The long-term forecast has temperatures climbing around 5 degrees above normal Friday and Saturday, but dense smoke may continue to slightly moderate the peak temperatures due to limited daytime mixing. Come Sunday, the aforementioned British Columbia trough will steer into our area and bring a dry cold frontal passage. Gusty winds and near or even slightly below normal temperatures will be expected Sunday through Monday. Tuesday will see a slight warming to near normal temperatures. Otherwise, considerably dry conditions will persist through the extended period.

AVIATION /12Z Tuesday through Wednesday/

Issued 450 AM MDT TUE JUL 28 2026 Widespread wildfire smoke creating MVFR/IFR horizontal visibility, and significantly reduced slantwise visibility. Mtns obscured in smoke. Slight vis improvement in the late afternoon before degrading again during overnight/morning periods due to evening valley winds. Isolated thunderstorms will develop near KTWF in the afternoon, capable of outflows to 45 kt. Surface winds: SW- NW 5-15 kt. Valley gusts 20-25 kt in portions of E-Oregon in the evening through overnight. Winds aloft at 10kft MSL: SW 5-15 kt.

KBOI...Wildfire smoke resulting in MVFR/IFR visibility. Some improvement expected during the late afternoon, before degrading again during overnight/morning periods. Surface winds: light S-SE or variable this morning, returning to NW 6-12 kt late morning through afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Quality Alert until 2 PM MDT Friday for IDZ011>015-028-029- 033. Air Quality Alert until 1 PM MDT Wednesday for IDZ016-030. OR...Air Quality Alert until 1 PM MDT /noon PDT/ Wednesday for ORZ061>064.