textproduct: Boise

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/

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/

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 postion 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 /18Z Friday through Saturday/

Issued 1158 AM MDT FRI SEP 4 2026 Mostly VFR. Scattered showers and isolated thunderstorms this afternoon and tonight. Areas of MVFR/IFR and mountain obscuration in heaviest pcpn. Areas of MVFR/IFR in valley fog after 05/06z. Snow level 7.5k-9.0k feet MSL in E Oregon, and 8.5-10k feet in w-central ID. Surface winds: SW-NW 5-15 kt. Gusts to 25 kt this afternoon. Winds aloft at 10kft MSL: SW 15-25 kt.

KBOI...VFR with scattered showers this afternoon. A 20-30% chance of thunderstorms from 21Z-24Z. VFR tonight with a 30-40% chance of showers. Surface winds: NW 5-15 kt. Gusts to 20 kt this afternoon. Winds variable less than 5 kts after 05/06Z with areas of fog in the vicinity.

Weekend Outlook...Mostly VFR. Scattered showers Saturday morning. Activity decreasing from SW to NE late morning. Then, showers increasing again Sunday, with highest chances (50-70%) over east Oregon and w-central Idaho. Localized MVFR/IFR and mountain obscuration in heaviest pcpn. Areas of valley/low stratus Saturday/ Sunday mornings. SW-NW surface winds 5-10 kt with PM gusts to 20 kt.&&

BOI WATCHES/WARNINGS/ADVISORIES

ID...Flash Flood Watch until 7 PM MDT this evening for IDZ011-013. OR...Flash Flood Watch until 7 PM MDT /6 PM PDT/ this evening for ORZ061>063.