textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated afternoon thunderstorms today and Thursday, mainly forming over the central Idaho mountains, and southern Twin Falls County.

- Thunderstorms capable of producing gusty erratic outflow winds up to 40 mph.

- Scattered showers and isolated thunderstorms over southwest Idaho on Friday and Saturday capable of producing wetting rains.

SHORT TERM /Through Friday Night/

Issued 220 PM MDT WED AUG 26 2026 An intense anticyclone continues to dominate the weather pattern over the southwestern US, with the northern extent of an associated upper ridge continuing to support well above-normal temperatures across the region. This will also maintain a ribbon of moisture across southern and central Idaho, and continue to favor isolated to scattered thunderstorm development today and Thursday afternoon near the Nevada border into the central Idaho Mountains. Increasing flow aloft ahead of a strengthening upper trough over the Pac NW will bring increased breeziness to eastern Oregon, and eventually into western and central Idaho, with elevated to critical fire weather conditions expected. Isolated morning shower activity is also possible Thursday morning, but will pose limited impacts.

By Friday, a more significant increase in moisture will occur. This will promote scattered to widespread shower development on Friday. Ensemble guidance continues to support a focused band of shower development, spanning from near the NV/OR/ID border northeastward on Friday. Amounts are likely to remain under a quarter-inch in most locations. Temperatures will also cool significantly - on the order of 10-15 degrees - as more seasonable late summer temperatures finally take hold.

LONG TERM /Saturday through Wednesday/

Issued 22p PM MDT WED AUG 26 2026 An upper trough will bring cooler weather to the region over the weekend. A 20-50% chance of showers and lower probability of thunderstorms will cover Baker County in Oregon and much of SW Idaho on Saturday as the trough axis remains positioned to the west. Breezy westerly winds behind Fridays cold front will bring gusts of 20-30 mph Saturday afternoon. Drier and cooler air moves into the area on Sunday on the backside of the trough with gusty winds continuing across the Snake Plain. Temperatures are near normal on Saturday, then drop to 5-10 degrees below normal on Sunday, which puts lower elevations in the upper 70s. Brief ridging on Monday will keep dry conditions in place and bring a quick return to above normal temperatures. Models continue to advertise a progressive pattern for next week with another trough moving through the Pac NW Tue/Wed. Moisture in advance of this trough would favor a chance of showers/thunderstorms across w-central/s-central Idaho zones on Tuesday. Temperatures trend toward normal to slightly below normal starting Tuesday.

AVIATION /00Z Thursday through Friday/

Issued 518 PM MDT WED AUG 26 2026 Southwest flow aloft with isolated showers/thunderstorms possible this evening and overnight, mainly eastward from a KMYL to Jordan Valley Oregon line. A few showers could develop into thunderstorms with wind gusts to 20 kt overnight. Another round of showers/thunderstorms possible over higher terrain in central Idaho as well as south central Idaho (including KTWF/KJER) Thursday afternoon. Surface winds becoming variable less than 10 kt, then favoring a SW-NW direction 10-15 kt after 18Z Thursday. Winds could gust higher than 25 kt across eastern Oregon, including KBNO. Winds aloft at 10kft: SW 15-25 kt.

KBOI...VFR, with an isolated shower/thunderstorm withing range of the terminal overnight (20% chance). Winds becoming SE around 10 kt overnight, then back to WNW 10-12 kt after 18Z Thursday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Red Flag Warning from noon to 9 PM MDT Thursday for IDZ423. OR...Red Flag Warning from 11 AM to 8 PM PDT Thursday for ORZ670>672.