textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Record high temperatures this afternoon, where low lying areas will see highs in the 90s.

- A cold frontal passage brings very gusty winds, a slight chance of thunderstorms, and cooling conditions Wednesday.

- Just above normal temps through Friday before another cooldown this weekend, conditions stay dry and breezy.

SHORT TERM /Through Thursday Night/

Issued 230 PM MDT TUE MAY 12 2026 High pressure over the area, and mostly clear skies today will allow temps to climb through late this afternoon. Low-lying areas including the Snake Plain and valleys in the Boise Mountains, Weiser Basin, and Malheur County will see temps in the 90s for their afternoon highs. This threatens daily high temp records for many locations in Southwest Idaho and Southeast Oregon. Alongside the hot temps is exceptional dryness. The 18Z sounding revealed a nearly dry adiabatic atmosphere up to 500 mb. There is just enough moisture at this level to produce some altocumulus, and with visible virga there is a slim chance for strong winds near the clouds. Right now, this seems very unlikely given the depth of the dry layer and limited moisture available to convection.

Temperatures cool quickly after sunset as the focus shifts to a quickly encroaching upper level low moving inland. This low will carry a strong cold front through most of the intermountain west. The primary hazard for our area as this front moves through is the winds. Late in the morning through the early evening, wind gusts increase to 40-55 mph across open areas and ridges. A Wind Advisory has been issued in the areas expected to see the strongest winds. Outside of the advisory, winds will still gust 30-40 mph throughout the day save for a few very sheltered mountain valleys. Winds will kick up dust, especially along the front, leading to reduced visibilities. In the morning and early afternoon, as the front itself passes, thunderstorms will be possible. Gusts out of thunderstorms could locally enhance the already gusty conditions in parts of the upper Snake Plain. The enhancement could briefly take winds up to 60 mph. Forecasts, however, continue to favor thunderstorm development over the West Central and Central Idaho mountains. Moderate rain and small hail will also be possible in storms.

Winds finally begin to weaken after sunset, but remain elevated overnight. Behind the front, temps on Thursday will be seasonal across the area. Winds stay elevated through the day, especially in Central and South-Central Idaho and Central Oregon. While Tuesday is the driest day, afternoon minimum relative humidities remain in the teens for southern areas each day. The coincidence of dry air and gusty winds highlights elevated fire weather conditions, especially Wednesday.

LONG TERM /Friday through Tuesday/

Issued 230 PM MDT TUE MAY 12 2026 Good model agreement in the overall large scale pattern Friday through Sunday. Dry westerly flow Friday with temperatures around normal. A substantial cool down for the weekend (temperatures 10 degrees below normal) as a shortwave trough moves across the area. Not a lot of moisture expected with this system so there's only a low end chance (20-30 percent) of precipitation for northern Baker County and portions of the West Central and Boise Mountains. Expect breezy NW winds Saturday and Sunday afternoon, especially across Baker County and the Snake River Plain. Temperatures expected to trend up with dry conditions on Monday. Forecast uncertainty grows Tuesday with some model guidance suggesting another shortwave trough with limited moisture may move across the region.

AVIATION /00Z Wednesday through Thursday/

Issued 509 PM MDT TUE MAY 12 2026 VFR with some shallow convection near terrain this evening. Isolated storms could produce localized gusty winds. Significant cold front to pass through the area Wednesday morning, with a dramatic shift in wind direction and increase in wind speed. Frontal passage 15-17Z for Oregon sites and 17-20Z for Idaho locations. Surface winds SSE 10-20 kt with higher gusts this evening, becoming SSW 10-20 kt overnight, then WNW 20-30 kt with higher gusts after frontal passage. Periods of LLWS possible near the front. Winds aloft at 10kft MSL: SSW 20-25 kt.

KBOI...VFR. Significant cold frontal passage 17-19Z Wednesday, with strong winds expected. Surface winds ESE 10-12 kt with gusts in the evening, becoming WNW 20-25 kt with gusts to 35 kt after 17Z.

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.