textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Hot, dry, and windy on Wednesday afternoon with elevated fire weather conditions in the Owyhee Mountains and in the Magic Valley.

- Isolated PM showers and thunderstorms on Wednesday and Thursday across east-central Oregon and west-central Idaho as a cold front moves through.

- Mostly dry and breezy this weekend with temperatures swinging from around 10 degrees above normal on Friday to around 5 degrees below normal by Sunday.

SHORT TERM /Through Thursday Night/

Issued 336 PM MDT TUE JUN 2 2026 Warm and dry conditions will continue today with generally light winds across the forecast area thanks to a ridge of high pressure lingering through Wednesday morning. A weak shortwave trough will move through the region on Wednesday evening, bringing a slight chance of showers and thunderstorms primarily north of a Mountain Home, ID - Burns, OR line. The main hazards with these showers and thunderstorms will be gusty outflow winds up to 35 mph and lightning. Rainfall amounts will be low with any showers and thunderstorms that form, generally less than a quarter inch under the heaviest showers/thunderstorms. This shortwave will also bring a cold frontal passage to southwest Idaho, with wind gusts up to 40 mph and single digit relative humidity values in the Lower Snake River Valley during the late afternoon-evening. These hot, dry, and windy conditions will bring elevated fire weather conditions, with Red Flag Warnings in effect for fire zones 423, 424, and 426 in south central Idaho. Temperatures will moderate briefly on Thursday with breezy northwest winds in the Snake River Valley also keeping temperatures about ten degrees cooler than Wednesday.

LONG TERM /Friday through Tuesday/

Issued 336 PM MDT TUE JUN 2 2026 An intense upper-level low pressure system will move into the Pacific NW on Friday and gradually move across the international border through the weekend. As this system moves in, southwesterly flow aloft will spread over the region, providing a warming and drying trend on Friday. Temperatures will hover around 10 degrees above normal on Friday. With the strong low pressure moving east throughout the weekend, it will cause a cold front to move through the area. The primary threat with this system will be the winds gusting widespread 20-35 mph, with the higher terrain and southeast Oregon seeing gusts 30-40 mph. Current model guidance also suggests gusts of 30-45 mph through the Snake River Plain late Saturday afternoon into evening. High temperatures behind the cold front Saturday and Sunday will drop 10- 15 degrees from Friday and dip to slightly below normal by Sunday. The trough is expected to weaken as it moves inland, keeping the area mostly dry with a 10-15% chance of showers and thunderstorms over the west-central Idaho mountains and lower chances elsewhere.

For Monday, ensembles favor weak and short-lived upper-level ridging gradually building, with upper-level troughing again along the coast. Highs are favored to warm to 5-10 degrees above normal. Confidence about the forecast is lower Tuesday, with the proximity and intensity of the trough variable from model to model. Some have it overhead by Monday afternoon, while some keep it weaker with slower timing. This difference causes considerable forecast discrepancy for now.

AVIATION /00Z Wednesday through Thursday/

Issued 533 PM MDT TUE JUN 2 2026 Mainly VFR. Scattered showers and thunderstorms develop across eastern Oregon late Wed morning, spreading towards west-central Idaho Wed afternoon. Timing for possible terminal impacts is after 19Z at KBKE/KBNO, and after 21Z at all other sites. Surface winds: Generally W-N 6-12 kt this this evening, then variable less than 10 kt overnight. Becoming SW 5-15 kt with gusts to 25 kt, and gusty outflow winds 25-40 kt possible Wed afternoon. Winds aloft at 10kft MSL: W 10-25 kt.

KBOI...Mainly VFR. 30% chance of MVFR after 22Z as isolated thunderstorms develop late Wed afternoon with areas of blowing dust. Surface winds: N-NW 10kt switching to SE 5-10 kt overnight. SW 15 kt with some gusts to 25 kt. Gusty outflow winds possible after 03/22Z.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Red Flag Warning from 3 PM MDT until 9 PM MDT Wednesday for IDZ423-424 and IDZ426.

OR...None.