textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated afternoon thunderstorms Wednesday and Thursday, mainly forming over the central Idaho mountains, and southern Twin Falls County.

- Thunderstorms capable of producing gusty erratic outflow winds up to 40 mph.

- Scattered showers and isolated thunderstorms over southwest Idaho on Friday and Saturday capable of producing wetting rains.

SHORT TERM /Through Friday Night/

Issued 334 AM MDT WED AUG 26 2026 An upper level ridge axis will remain just east of the area through Thursday while low pressure remains situated off the Pacific Northwest. This will keep southwest flow over the area with above normal temperatures continuing. Breezy southwest winds expected on Wednesday and Thursday afternoon over eastern OR and the southwest ID highlands. Enough moisture remains over southwest Idaho for isolated afternoon thunderstorms Wednesday and Thursday, mainly forming over the central ID mountains, and southern Twin Falls County. Gusty outflow winds up to 45 mph will be the main threat with thunderstorms, most favored in the Magic Valley and southern Twin Falls County. Tropical Storm Iselle, just off of Baja California, is forecast to dissipate and portions of the remnants will get ingested into the southwest flow aloft off the CA coast and move over southwest Idaho and extreme SE Oregon on Friday afternoon. Magic Valley precipitable waters briefly reach the 98th percentile with this feature so heavy rain will be a threat with storms that form across the southwest ID highlands, central ID mountains and southern Twin Falls County. Latest RRFS is showing more of a stratiform rain event now, with scattered showers and isolated thunderstorms capable of producing wetting rains (greater than 0.10 inch) over much of eastern OR and southwest ID.

LONG TERM /Saturday through Wednesday/

Issued 334 AM MDT WED AUG 26 2026 Upper level trough over BC will continue over the long term with below normal temperatures and a slight chance of showers and thunderstorms. Temperatures will be near normal Saturday before cooling to below normal Sunday as a dry cold front moves through. Another trough digging along the BC coast will shift the flow to southwest on Monday, and bring warmer temperatures ahead of the next cold front. A cold front will move through the area on Tuesday bringing cooler temperatures and below normal temperatures Tuesday and Wednesday. Uncertainty remains elevated in the extended period, as tropical activity in the Pacific enhances the jet stream. Models do not handle the energy transfer well in these situations so expect lots of changes in the far extended period over the next week.

AVIATION /12Z Wednesday through Thursday/

Issued 635 AM MDT WED AUG 26 2026 VFR. Isolated showers and virga during morning hours. A slight chance of thunder. Then, isolated showers and thunderstorms near KTWF/KJER and over central ID mtns in the afternoon/eve. Outflows 30-45 kt. High density altitude in the afternoon due to heat. Areas of smoke near wildfires degrading visibility. Surface winds: E-SE 5-15 kt this morning, then mainly SW-SE 5-15 kt with gusts around 20 kt in the afternoon. Winds aloft at 10kft MSL: SW 15-25 kt.

KBOI...VFR. Isolated showers in vicinity this morning. High density altitude in the afternoon. Surface winds: SE 5-15 kt except turning NW 5-10kt during the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Fire Weather Watch from Thursday afternoon through Thursday evening for IDZ423. OR...Fire Weather Watch from Thursday morning through Thursday evening for ORZ670>672. Air Quality Alert until noon PDT today for ORZ062.