textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Above normal temperatures through next week with Tuesday and Friday being the hottest days. - The hot temperatures Tuesday and Wednesday will be accompanied by gusty winds and very dry conditions.

- A chance of showers and thunderstorms returns to the area Friday and Saturday.

SHORT TERM /Through Wednesday Night/

Issued 304 AM MDT MON JUN 15 2026 An upper level ridge centered off the coast will continue to amplify and shift eastward over the Interior West. Strong subsidence beneath the building ridge will cause temperatures to surge. High temperatures on today will reach 10 to 15 degrees above normal, pushing lower elevation valleys well into the 90s. Tuesday is expected to be the hottest day of the short term period as the ridge axis moves directly overhead.

A tightening surface pressure gradient and deep mixing will allow stronger flow aloft to mix down to the surface Tuesday afternoon. Gusty west to northwest winds will develop across the region. The strongest winds will impact the higher terrain and the Snake River Plain east of Mountain Home, where gusts of 25 to 35 mph are expected. The combination of unseasonably hot temperatures, low relative humidity, and gusty winds will drive elevated fire weather concerns across our grassy and shrubby fuel types.

On Wednesday, an upper level trough moving across western Canada will flatten the ridge and drag a weak, dry cold front through the Pacific Northwest. This will drop temperatures by 5 to 10 degrees compared to Tuesday. However, breezy post-frontal winds combined with an ongoing very dry airmass will likely carry the elevated fire weather concerns from Tuesday straight into Wednesday.

LONG TERM /Thursday through Monday/

Issued 304 AM MDT MON JUN 15 2026 The upper ridge quickly reamplifies over the Great Basin on Thursday and Friday. High temperatures will climb right back to around 10 degrees above normal on Thursday, and 10 to 15 degrees above normal by Friday. This second heating peak on Friday will bring valley temperatures to within just a few degrees of Tuesday's hot conditions.

Model guidance remains in relatively good agreement that a deeper, more energetic upper level trough will approach the Pacific Northwest coast late Friday and move inland over the weekend. This incoming system will introduce cooler temperatures, but it will also tap into better moisture. A chance of showers and thunderstorms will return to southeast Oregon and southwest Idaho starting Friday afternoon, expanding eastward into Saturday. Given the preceding hot and dry conditions, lightning striking dry fuels could create a critical fire weather setup. Behind the main trough axis, winds are forecast to ramp up across the upper Snake River Plain on Saturday and Sunday.

AVIATION /18Z Monday through Tuesday/

Issued 1212 PM MDT MON JUN 15 2026 VFR with high clouds moving in this evening and tonight. Surface winds: variable becoming W-NW 5-15 kt this afternoon. KBOI...VFR with high clouds tonight. Surface winds: NW 6-10 kt with periodic gusts up to 18 kt possible this afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.