textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Cold front and gusty winds this evening, followed by breezy and slightly cooler weather Friday, then warmer again Saturday.

- Much stronger cold front late Saturday and Saturday night with wind gusts 35 to 45 mph in southern areas, and widespread showers and scattered thunderstorms in the north.

- Windy and much cooler Sunday, with showers continuing in the north.

- Warming and drying Monday and beyond.

SHORT TERM /Through Sunday Night/

Issued 206 PM MDT THU SEP 10 2026 Mid to high level clouds are slowly building in over the area from the south this afternoon, with isolated virga showers/thunderstorms near the NV border through late this evening. A dry cold front will sweep across the area later today, bringing some elevated winds westerly winds this afternoon through around sunset. Elevated wind breezes will return Friday afternoon, while temperatures drop but remain warmer than normal.

The major highlight of the short-term is the active pattern arriving this weekend. Latest guidance slightly delayed the Pacific upper low's arrival to Saturday night. Ahead of this low, our area will stay under a strong southwest flow, returning warm temperatures up to 10 degrees above normal and sustaining dry conditions throughout the daytime hours on Saturday. The strong southwesterly winds with gusts up 45 mph, combined with low RHs, will bring heightened fire weather concerns for the southern areas near the ID/NV border.

The upper low will steer a strong cold front Saturday evening through overnight, sustaining strong westerly winds and bringing chances of precipitation over most of the area. The northern half of our CWA will continue to see the bulk of the precipitation, with the west central ID and east central OR mountains seeing the highest likelihoods of heavy rain and embedded scattered thunderstorms. There is considerable guidance uncertainty over how much precipitation the lower valleys will see. For now, the lower Treasure Valley area will generally see total rainfall of around 0.01 to 0.05" and a 10-15% chance of thunderstorms late Saturday through early Sunday.

LONG TERM /Monday through Friday/

Issued 206 PM MDT THU SEP 10 2026 On Sunday, moderate to high precipitation chances will remain over the northernmost mountain areas of our CWA, before tapering off in the afternoon. Otherwise, a rapid cooling trend will be in store for Sunday, with temperatures dropping well below normal following the cold frontal passage. Snow levels will drop down to the 7000-8000 ft range through Sunday morning, favoring some light snowfall over high mountain peaks. By late Sunday, our western zones should clear, and Sunday night will be cold and mostly clear area-wide, except for valley fog early Monday morning. Otherwise, Monday will continue to see temperatures slightly below normal. A large ridge of high pressure will rebuild over the northwest region and bring a warming and drying trend through the rest of the week.

AVIATION /06Z Friday through Saturday/

Issued 1207 AM MDT FRI SEP 11 2026

VFR. Isolated thunderstorms/virga near ID-NV border through Fri/08Z, capable of gusty outflows 30-35 kt. Surface winds: SW- NW 15 kt or less overnight, becoming W-NW 5-15 kt Friday. Winds aloft at 10kft MSL: SW-W 25-35 kt.

KBOI...VFR with scattered mid-level clouds. Surface winds: SE 5-10 kt, then NW-N 4-8 kt after 11/12z.

Weekend Outlook...VFR with increasing SW surface winds in OR Saturday afternoon. Cold front with gusty southwest winds, widespread showers, and scattered thunderstorms late Saturday, mainly in Baker County, OR and north of the Snake Basin in ID. MVFR conditions and mountain obscuration in precip. Showers, mountain valley fog, and MVFR conditions continuing Sunday morning in west-central ID before improving in the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Fire Weather Watch from Saturday afternoon through Saturday evening for IDZ423-426. OR...None.