textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Cloudy skies and isolated light rain showers tonight and Monday.

- Clearing Monday night, then sunny warmer days Tuesday through Friday.

- Breezy northwest winds afternoons and evenings in the Snake Basin east of Boise the next several days.

SHORT TERM /Through Tuesday Night/

Issued 210 PM MDT SUN SEP 27 2026 A weak northward-moving warm front has spread clouds over our CWA, with a few light rain showers detected by radar in northern Malheur County. This front was the former cold front that passed through our CWA on Friday, but returned northward under southwesterly flow aloft as a Pacific upper trough reached the west coast. The current warm front doesn't have much rain with it but what little there is will be focused over Harney County this evening, decreasing by midnight, then reappearing overnight and Monday morning in Owyhee County northeastward through the Boise Mountains. Instability looks too weak to support thunderstorms either today or Monday. Meanwhile, the upper trough will close off a low as it moves inland, headed into southern California Monday and Arizona Tuesday. The low will take the frontal band eastward and out of our Oregon zones Monday and our Idaho zones Monday night, bringing clearing skies and cooler nighttime temps. Tuesday looks sunny and warmer as an upper ridge replaces the departing low. Wind this evening will be breezy northwesterly (15-25 mph) between Boise and Twin Falls, and lighter elsewhere. Similar winds are expected the next several afternoons/evenings.

LONG TERM /Wednesday through Sunday/

Issued 210 PM MDT SUN SEP 27 2026 High pressure building off the Four Corners region will continue warm and dry conditions Wednesday through late week. A mostly flat trough steering east across the northwest region will bring a dry cold front across the area on Wednesday. This frontal passage will return elevated wind breezes, mainly over the southwest ID side. A large Pacific high pressure will then build in Thursday through Friday, brining unseasonably warm temperatures about 10 degrees above normal for both those days. Come late Friday, another mostly dry shortwave trough will dig across the northwest region, returning a cooling trend through Saturday. Sunday may see the return of warmer than normal temperatures, depending on the extent of Pacific ridge building over the Great Basin.

AVIATION /00Z Monday through Tuesday/

Issued 520 PM MDT SUN SEP 27 2026 Generally VFR. Virga and isolated rain showers mainly over SE Oregon and the central ID mountains. Patchy fog in sheltered mountain valleys overnight through Monday morning. Surface winds: W- NW 5-15 kt, with gusts to 25 kt south/east of KBOI. Winds aloft at 10kft MSL: S-SW 10-20 kt becoming variable under 15 kts after Mon/06z.

KBOI...VFR with dense mid-high cloud coverage. Virga/light showers remain in the vicinity overnight. Surface winds: NW 7-14 kt, with gusts to around 20 kt late afternoon through evening.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.