textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Showers and thunderstorms with local heavy rain today.

- Areas of valley fog late tonight and early Saturday morning.

- Temperatures 10 to 20 degrees below normal today, then around 10 degrees below normal Saturday and Sunday.

- Cool Monday, then warming next week, with an increasing chance of thunderstorms Wednesday afternoon through Friday.

SHORT TERM /Through Sunday Night/

Issued 254 PM MDT FRI SEP 4 2026 An upper level trough will remain along the Oregon coast over the next day with a front stalled out over southwest Idaho. Showers along the front this afternoon have kept temperatures well below forecast from Rome OR to Boise ID to the central ID mountains. Partial clearing in eastern OR has allowed conditions to destabilize with isolated thunderstorms developing in eastern OR late this afternoon, and near the Owyhee Mountains. Isolated showers will continue overnight across the Boise mountains before tapering off on Saturday afternoon as drier air moves in from the southwest. Showers and thunderstorms will generally be confined north and west of Baker County in OR and northeast of Valley County in ID. The trough will begin to move inland on Sunday and across southern ID late Sunday night, with showers and thunderstorms areawide.

LONG TERM /Monday through Friday/

Issued 254 PM MDT FRI SEP 4 2026 High pressure aloft will start to build over the area Monday/Monday night as an upper low exits the region across Montana into southern Canada. The higher pressure will bring warmer air back into our CWA the rest of the week, with temperatures approaching normal Wednesday and beyond. Drier air will spread over the area Tuesday but moisture will be on the increase again later in the week as the next upper low is forecast to move into position near the Pacific Northwest coast while southwesterly flow aloft taps into moisture from the next westward-moving hurricane in the Pacific subtropics. We therefore have a 20 percent chance of showers and thunderstorms in the forecast as early as Wednesday afternoon near the Nevada border, increasing to 20-40 percent across the forecast area Thursday and Friday.

AVIATION /06Z Saturday through Sunday/

Issued 1039 PM MDT FRI SEP 4 2026 Mainly VFR. Scattered showers continue overnight. Areas of MVFR/IFR and mountain obscuration in heaviest precipitation. Areas of MVFR/IFR in valley fog through early Sat morning. Snow level 8k-10k feet MSL. Isolated showers and thunderstorms after 05/20Z in eastern Oregon, and dry elsewhere. Surface winds: Variable through late morning, becoming SSW 5-10 kt this afternoon. Winds aloft at 10kft MSL: SW 15-25 kt.

KBOI...VFR. Intermittent showers continue through early morning. Areas of fog developing early Sat morning, but low confidence (30% chance) of affecting the terminal. Winds generally light and variable.

Sunday Outlook...Scattered showers and thunderstorm developing area-wide Sunday afternoon, with potential for brief heavy rain and gusty outflow winds. Areas of valley low stratus/fog Sunday morning. SW-NW surface winds 5-15 kt with PM gusts to 20kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.