textproduct: Boise

UPDATE

Updated aviation discussion. Corrected wording.

KEY MESSAGES

- Very hot Tuesday. Record high temperatures in the 90s in the lower valleys.

- Becoming very windy and turning much cooler from west to east Wednesday, with showers and chance of thunderstorms along and behind a strong Pacific cold front.

- Slightly warmer Friday, then turning cooler again Saturday and Sunday, with light snow possible above 6000 feet in northern mountains.

SHORT TERM /Through Wednesday Night/

Issued 213 PM MDT MON MAY 11 2026 After today's slight cooling, Tuesday will be about 10 degrees hotter as an anomalously strong upper ridge passes directly overhead. Models have come into close agreement on high temps for Tuesday, with 90s in southern valleys and 80s elsewhere, hot enough to set records for the date. The ridge will exit east Tuesday evening as a deep Pacific upper low, located near 43N/143W at 18Z, moves due east. The low is forecast to reach the Oregon coast around 12Z Wednesday when the slower-moving ridge is along the Continental Divide. A steep height and thermal gradient will develop between the ridge and the low resulting in formation of a strong surface cold front. The front is forecast to reach western Harney County 10 AM PDT Wednesday, the OR/ID border around 3 PM MDT Wednesday, and south-central Idaho 6-8 PM MDT Wednesday evening. The forward speed of the front, together with the steep thermal gradient across the front, will produce strong winds and sharp cooling as the front passes, especially in southern areas. We have issued a Wind Advisory for this event, expecting 25 to 35 mph sustained winds with gusts to 55 mph. Rising air ahead of the front will support a chance of showers and thunderstorms right along the front. Blowing dust may reduce visibility in areas that don't receive rain. Behind the front temperatures will lower further while west winds continue 15 to 30 mph into Wednesday evening. High temps Wednesday will be as much as 30 degrees cooler than Tuesday's highs in Harney County, with less cooling on the Idaho side, where the remaining cooling will come Thursday. More showers will pass through our CWA Wednesday night, most numerous in northern areas, with snow on the higher peaks by Thursday morning.

LONG TERM /Thursday through Monday/

Issued 213 PM MDT MON MAY 11 2026 An upper level trough will move east of the area on Thursday leaving the area under drier northwest flow aloft and 20 percent chance of showers over the mountains of SW Idaho. Breezy west to northwest winds Thursday especially across the Magic Valley with daytime highs around normal. Dry zonal flow on Friday with temperatures trending up a few degrees. Models display some variation of troughing over the region Saturday/Sunday. This will bring cooler weather and a 20-30 percent chance of rain/snow showers to the northern mountains with snow levels 5000-6000 feet MSL. Weekend temperatures expected to be 5 to 10 degrees below normal with breezy northwest winds across the Upper Treasure and Magic Valleys. Dry on Monday with temperatures trending up under west to northwest flow aloft.

AVIATION /00Z Tuesday through Wednesday/

Issued 527 PM MDT MON MAY 11 2026 VFR, with scattered high clouds above 20kft. Winds NW 5-15 kt with higher gusts into the early evening, becoming less than 10 kt overnight, then increasing to ESE Tuesday afternoon. ESE winds strongest over the Magic Valley of Idaho, with values of 10-20 kt with gusts to 25+ kt possible. High density altitude possible 20- 23Z Tuesday.

KBOI...VFR. Some high clouds. Winds becoming SE overnight less than 10 kt, increasing to SE 8-10 kt with gusts to 15 kt after 20Z Tuesday. High density altitude possible 20-23Z Tuesday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Wind Advisory from noon Wednesday to midnight MDT Wednesday night for IDZ012-014>016-028>030. OR...Wind Advisory from noon MDT /11 AM PDT/ Wednesday to midnight MDT /11 PM PDT/ Wednesday night for ORZ063-064.