textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Dry and warmer through Thursday.

- Cold front and gusty winds Thursday evening, followed by breezy and cooler weather Friday.

- Much stronger cold front late Saturday with gusty winds, showers, and thunderstorms, then windy and much cooler Sunday.

- Warming and drying next week.

SHORT TERM /Through Friday Night/

Issued 213 AM MDT WED SEP 9 2026 Yesterday's weak secondary upper low has moved away leaving our CWA dry and forecast to warm under WNW-ly flow aloft through most of Thursday. Thursday's highs will be in the upper 70s through 80s, with a couple of spots (e.g., Grand View/ID and Rome/OR) near 90. Meanwhile, an upper trough will dig southward through western Canada and into the nwrn US. The trough will push a dry surface cold front through our CWA Thursday night with gusty west winds and a couple hours of cloudiness. Friday looks sunny, breezy, and 5 to 10 degrees cooler, and Friday night looks mostly clear and seasonably cool. But the real weather will come Saturday through Sunday (below).

LONG TERM /Saturday through Wednesday/

Issued 213 AM MDT WED SEP 9 2026 Latest models move a deep, compact upper low off the WA coast rapidly inland across OR Saturday, then right through our CWA Saturday night, and into MT Sunday. What makes this unusual is how fast the low moves for a closed system, and for that reason we are expecting a strong cold front to pass through our CWA Saturday evening, with showers, chance of thunderstorms, strong winds, and rapidly falling temperatures. No highlights will issued just yet as the event is still 4 days away, but confidence is growing with models already in good agreement. Showers, possibly heavy, will continue Sunday morning as moisture wraps around the northern and western flanks of the eastward-moving upper low. By late Sunday our western zones should clear, and Sunday night looks clear and cold CWA-wide, except for valley fog early Monday morning. Then sunny and warmer Monday before the next upper trough digs SSW-ward from BC and forms another low off the WA/OR coast. Tuesday and Wednesday should be dry and warming as models (especially GFS) keep that low off the coast.

AVIATION /12Z Wednesday through Thursday/

Issued 506 AM MDT WED SEP 9 2026 VFR with generally clear skies. Patchy fog in sheltered mountain valleys through mid morning. Surface winds: Variable less than 10 kt. Winds aloft at 10kft MSL: W-NW 10-20 kt.

KBOI...VFR. Clear skies. Surface winds: SE under 8 kt until mid-morning, then light NW.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None. OR...None.