textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Scattered showers and isolated thunderstorms through Saturday. Stronger storms possible in SW Idaho on Saturday.

- Cool and dry Sunday then warmer early next week.

- A deeper low pressure system expected later next week for cooler and wetter conditions.

SHORT TERM /Through Sunday Night/

Issued 227 PM MDT FRI AUG 28 2026 Showers will and isolated thunderstorms will continue across southwest Idaho and far SE Oregon into Saturday. A couple of highlights include shortwave energy lifting out of the Great Basin this evening and a cold frontal passage Saturday evening. The shortwave trough this evening will act to increase the potential for thunderstorms from the OR/ID/NV border area northeastward into the Boise mtns through late evening. Gusty winds to 40 mph would be the main threat from heavier showers and thunderstorms through Midnight. Shower and thunderstorm potential will continue across SW Idaho on Saturday, while dropping off across SE Oregon. Passage of a cold front Saturday evening will usher in a cooler air mass on gusty northwest winds. Precipitation will taper off behind the front Saturday night leaving dry conditions across the region on Sunday. Temperatures Sunday will run about 10 degrees below normal, putting lower elevations in the upper 70s. Sunday night will be dry with many sites dropping into the upper 40s or colder.

LONG TERM /Monday through Friday/

Issued 227 PM MDT FRI AUG 28 2026 Conditions slowly cool and become more active through the long term as a broad trough along the coast amplifies and a strong closed low pressure system moves along the trough axis. As the trough axis develops Monday and Tuesday, most of the area moves into the deformation zone between a shortwave ridge and shortwave trough. This means rebounding up to seasonal averages on Monday inside the ridge, and increased shower and thunderstorm chances in south central Idaho. The shortwave ridge moves out Tuesday as another shortwave trough moves through, this time further north and west, covering much of the forecast area. Temps are mostly unchanged Monday into Tuesday, but enhanced storm potential moves from south central Idaho over higher terrain in central and southwestern Idaho as well as eastern Oregon.

Temperatures cool properly to 10 degrees below normal Wednesday through Friday as the strong closed low moves along the trough axis and stalls over the Oregon coast. Unsettled and gusty conditions are expected in the broader region, although the exact placement of storms/showers is still uncertain. The strong pressure gradient aloft is likely to mix down to the surface ahead of the low, leading to widespread gusts each afternoon Tuesday through the extended period.

AVIATION /00Z Saturday through Sunday/

Issued 606 PM MDT FRI AUG 28 2026 Light rain showers and virga across S Idaho and far SE Oregon will continue tonight into Saturday. Isolated embedded thunderstorms will also develop with gusty erratic winds 25-40 kt possible this evening and again Saturday. Patchy morning fog in the west central Idaho mountains in the morning. Local reductions in visibility from wildfire smoke. Surface winds: SE-W 5-15 kt, becoming NW Saturday evening. Gusts SW 20-35 kt this evening across SE Oregon and far SW Idaho, diminishing overnight. Gusts 20-30 kt Saturday afternoon/evening. Winds aloft at 10kft MSL: SW 15-30 kt.

KBOI...Overcast mid-level clouds. Occasional light showers/virga in the vicinity through Saturday. Surface winds SE 5-15 kt with gusts up to 30 kts briefly possible this evening, becoming light and variable by Saturday morning.

Sunday Outlook...Decreasing clouds and dry. Surface winds W-NW 5-15 kt, afternoon gusts 20-25 kt in S-central Idaho.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.