textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Heat Advisory through this evening in the Treasure Valley, western Magic Valley, and Upper Weiser River Valley.

- Monsoon moisture will bring a chance of showers and thunderstorms Friday through Tuesday.

- A cold front will bring strong thunderstorms to the area on Saturday afternoon and evening.

- Thunderstorms capable of producing gusty outflow winds up to 50 mph with areas of blowing dust.

SHORT TERM /Through Sunday Night/

Issued 420 AM MDT FRI AUG 21 2026 A ridge will remain over the area with continued hot conditions. A trough remains off the OR coast, bringing southerly flow to the area over the next few days. Winds each afternoon will be breezy south-southwest ahead of a cold front that arrives late Saturday. Monsoon moisture will increase today to the 85 to 90th percentile through Saturday, with a 15-25 percent chance of showers and thunderstorms. Increasing clouds late this afternoon, which may lower temperatures a few degrees from the forecast. Quite a bit of range in temperatures today with the cloud cover uncertainty, with a few models showing up to 105 across the Snake Plain this afternoon under full sun. A cold front will enhance shear aloft for the possibility of strong organized thunderstorms on Saturday afternoon and evening. The front will bring drier air to the area on Sunday with breezy westerly winds. Temperatures will be around 10-15 degrees above normal Friday, lowering to near normal by Sunday.

LONG TERM /Monday through Friday/

Issued 420 AM MDT FRI AUG 21 2026 Southwest flow continues in the long term with monsoon moisture keeping a threat of showers and storms over southwest ID. Models show a potent shortwave moving over the area on Monday afternoon with a 15 to 25 percent chance of showers and storms over southwest ID. Forecast may need to be adjusted higher in eastern OR for this shortwave. A trough off the Pac NW coast pushes the monsoon moisture east on Tuesday with drier air, breezy conditions and slightly cooler temperatures Tuesday through Friday. Temperatures will around 2-5 degrees above normal through the period.

AVIATION /12Z Friday through Saturday/

Issued 624 AM MDT FRI AUG 21 2026 VFR. High density altitude this afternoon from heat. Areas of wildfire smoke. Increasing clouds with isolated showers/thunderstorms Friday evening through Saturday morning. Surface winds: variable 5-10kt, showers and storms capable of gusty erratic outflows up to 50 kt this evening. Winds aloft at 10kft MSL: SW-SE 15-25 kt.

KBOI...VFR. 10-20% chance of showers and thunderstorms over terminal after Sat/00Z. Surface winds: variable 5-10kt, gusty outflow winds 30-50kt possible this evening from the southwest- southeast.

Weekend Outlook...Scattered showers and thunderstorms continuing Saturday. Gusty outflow winds 30-45 kt and locally heavy rain from storms. Drier Sunday. Areas of wildfire smoke. Gusty SW winds Saturday afternoon. Breezy W-NW winds all areas on Sunday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Heat Advisory until 9 PM MDT this evening for IDZ012-014-016- 033. OR...Heat Advisory until 9 PM MDT /8 PM PDT/ this evening for ORZ064. Fire Weather Watch from Saturday afternoon through Saturday evening for ORZ670>672.