textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

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

- Thunderstorms capable of producing gusty erratic outflow winds up to 45 mph.

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

SHORT TERM /Through Saturday Night/

Issued 408 AM MDT THU AUG 27 2026 An upper level ridge axis will remain just east of the area through Thursday while low pressure remains situated off the Pacific Northwest. This will keep southwest flow over the area with above normal temperatures today. Breezy southwest winds expected this afternoon over eastern OR and the southwest ID highlands. Enough moisture remains over southwest Idaho for isolated afternoon thunderstorms today, mainly forming over the central ID mountains, and southern Twin Falls County. Gusty outflow winds up to 45 mph will be the main threat with thunderstorms, most favored in the Magic Valley and southern Twin Falls County. By Friday, a more significant increase in moisture aloft 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. Showers and isolated thunderstorms continue into Saturday morning before drier air moves in from the west. Precipitation amounts are likely to remain under a quarter-inch in most locations. Temperatures will also cool around 10-15 degrees to around 2-5 degrees below normal Friday and Saturday.

LONG TERM /Sunday through Thursday/

Issued 408 AM MDT THU AUG 27 2026 Upper level trough over BC will continue over the long term with below normal temperatures and a slight chance of showers and thunderstorms. Temperatures on Sunday cool a few more degrees behind the cold front as the trough passes by to the north. Another trough digging along the BC coast will shift the flow to southwest on Monday, and bring warmer temperatures ahead of the next cold front. A cold front will move through the area on Tuesday bringing cooler temperatures and below normal temperatures Tuesday and Wednesday. The trough anchors itself over the Pacific Northwest after Thursday, with temperatures lowering to around 10-15 degrees BELOW normal for the first time in a long time. 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 /18Z Thursday through Friday/

Issued 1127 AM MDT THU AUG 27 2026

Isolated showers in Idaho this morning move to the NE this afternoon. Stronger showers and storms redevelop SE of the Magic Valley this afternoon. Chance of thunder at the airports is low, but outflows from distant storms could bring gusty erratic winds. Tomorrow morning, widespread light rain and virga moves across the area. Surface winds SW-NW 10-20kt with gusts to 30kt over the higher terrain this afternoon. Winds aloft at 10kft MSL: SW 15-25kt.

KBOI...VFR, with a very low chance of showers in the vicinity this afternoon. Surface winds SE 5-10kt this morning shifting to W-NW 5-15kt through the afternoon.

Weekend Outlook...VFR. Patchy morning fog in the west central ID mountains and scattered showers on Saturday through the day in ID. Slight chance of thunderstorms Saturday afternoon. Breezy SW-NW Surface winds Saturday. Dry conditions 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.