textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated thunderstorms through this evening, mainly over south-central Idaho.

- Scattered showers and isolated thunderstorms Friday and Saturday. Stronger storms possible in SE Oregon on Friday.

- Notable temperature swings from Sunday through next week with Monday and and Tuesday being the warmest days.

SHORT TERM /Through Saturday Night/

Issued 155 PM MDT THU AUG 27 2026 A trough off the Pac NW coast will bring a break from the heat heading into the weekend. Isolated thunderstorms will remain in play across s-central Idaho zones through this evening. Stronger storms are expected to stay east of Jerome/Twin Falls counties, so probability of gusty outflow winds to 40 mph is low. Critical fire weather conditions for gusty winds (to 35 mph) and low relative humidity (~10%) will continue across SE Oregon and Owyhee County in SW Idaho into this evening. Clouds will increase tonight with precipitation developing Friday morning as the upper trough edges inland. The focus of showers and isolated thunderstorms on Friday will be across SW Idaho and far eastern Oregon. Central/southern Harney and Malheur counties will be positioned along the western edge of cloud/precip shield by Friday afternoon which would support higher thunderstorm chances and possibly stronger storms in this area. Several of the CAMs along with the REFS are highlighting this potential with gusty outflow winds to 50 mph possible. The chance of precipitation exits SE Oregon Friday night, but will linger across SW Idaho on Saturday as the upper trough slowly works inland. A cold front will push through the area Saturday evening bringing drier conditions and breezy winds with gusts to 30 mph.

LONG TERM /Sunday through Thursday/

Issued 155 PM MDT THU AUG 27 2026 As one trough moves east, another one slots in along the coast. On Sunday, this puts us into the dry deformation zone, and allows temperatures to climb into Monday. Sunday will be one of the cooler days in the long term about 10 degrees below normal, warming up to near normal on Monday. Monday evening, the coastal trough moves inland, and could produce storms in S-Central Idaho. The bulk of the activity will be over the four-corners states, so models vary on how far the northwestern fringe moves into Idaho, but it does appear to be a potent shortwave. Storms will be capable of heavy rainfall, small hail, and gusty winds. Tuesday evening, yet another trough moves in the Pacific NW coast for storms over Central Idaho and Eastern Oregon. The trough comes ahead of the core of the low pressure, set to move in later in the week with very low heights, a strong pressure gradient, a big cool down and some potentially strong winds. Uncertainty remains elevated in the extended period, as tropical activity in the Pacific enhances the jet stream. Models do not handle the energy transfer well in these situations so expect lots of changes in the far extended period over the next week with all these tropical systems.

AVIATION /00Z Friday through Saturday/

Issued 621 PM MDT THU AUG 27 2026 Mainly VFR. Scattered showers and isolated thunderstorms along the Idaho/Nevada border this evening. Chance of thunder at the Magic Valley terminals is low, but outflows from distant storms could bring gusty erratic winds. Light rain and virga will increase late tonight into Friday across S Idaho and far SE Oregon. Isolated embedded thunderstorms will also develop with gusty erratic winds 25-45 kt possible. Local reductions in visibility from wildfire smoke. Surface winds: SW-NW 5-15 kt, gusts to 25 kt Friday afternoon. Winds aloft at 10kft MSL: SW 15-25 kt.

KBOI...VFR. Increasing mid to high clouds with light showers or virga in the vicinity late tonight into Friday. Surface winds variable less than 10 kt tonight, then SE 5-15 kt developing by early Friday morning.

Weekend Outlook...Mainly VFR. Patchy morning fog in the west central Idaho mountains and scattered showers on Saturday through the day in Idaho, mainly in the mountains. Slight chance of thunderstorms Saturday afternoon. SW-NW surface winds 5-15 kt with gusts to around 25 kt Saturday. Breezy W-NW winds and dry on Sunday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Red Flag Warning until 9 PM MDT this evening for IDZ423. OR...Red Flag Warning until 8 PM PDT this evening for ORZ670>672.