textproduct: Boise

KEY MESSAGES

- Scattered showers and thunderstorms today across far eastern Oregon and far western Idaho, with gusty winds, lightning, brief heavy rain, and small hail possible.

- Very hot, dry, and breezy to end the week.

- Areas of smoke will continue through the week.

SHORT TERM /Through Saturday Night/

An upper level low will spin off the coast today while an upper level ridge begins to move to the east. This will usher in southwesterly flow aloft, which will begin to push out deeper monsoonal moisture. However, an area of moisture and instability located over central Oregon this morning will move over the Idaho/Oregon border this afternoon and early evening before drier air arrives. Strong daytime heating will allow scattered showers and thunderstorms to develop across far eastern Oregon and far western Idaho, then drift northeast. Forecast soundings reveal higher instability in the Treasure Valley today than previous days, indicating potential for storms to reach the Boise Metro area. Gusts up to 40-60 mph will be possible along with frequent lightning, brief heavy rain, and small hail. Southwest flow will also bring hotter temperatures with lower valleys reaching 100-105 degrees, with a Heat Advisory beginning this afternoon due to heat-related impacts. Winds will become breezy across south-central Oregon this afternoon with gusts to 25 mph. Wildfire smoke will persist across the area today with some improvement in the afternoon.

On Friday and Saturday, very dry air will arrive from the west as the low slowly approaches the coast and southwest flow aloft increases. Winds will become breezy each afternoon, strongest on Saturday as the upper level low moves into western Washington. Gusts Saturday across southeast Oregon and the higher elevations of southwest Idaho could reach 30-40 mph. Very dry air combined with gusty winds may bring critical fire weather conditions. Temperatures will remain very hot, especially on Friday when some lower valley locations will approach 107 degrees. Shower and thunderstorm potential (10-20% chance) will be limited to south-central Idaho, where monsoonal moisture will hang on for a couple more days. Wildfire smoke will linger over the area, mainly each night and morning with daytime mixing improving afternoon conditions.

LONG TERM /Sunday through Thursday/

The pattern through the extended will be very similar to late this week, but more moderated with slow day-to-day changes. An upper level trough along/off the coast and upper level ridging to our east will continue dry southwest flow across the area. Temperatures will remain hot, although slightly cooler thanks to the trough with lower valleys reaching the mid 90s. Temperatures may increase several degrees by the end of the period as the ridge builds back to the west. Winds will remain breezy, but not as strong as Saturday due to a weaker pressure gradient. Dry air will keep shower and thunderstorm chances minimal, but will tick up across south-central Idaho to 10-20% by mid to late week as the ridge expands and allows monsoonal moisture back into eastern areas.

AVIATION /06Z Thursday through Friday/

Issued 1148 PM MDT WED JUL 22 2026 Generally VFR, with areas of MVFR due to wildfire smoke. Visibility will be at a minimum overnight, with improvement during the peak of daytime heating. Showers and thunderstorms will linger into the overnight hours across eastern Oregon, then flare again Thursday afternoon. Surface winds: variable less than 10 kt overnight, except vrb15g25kt near storms, becoming WNW 10-15 kt after 20Z. Winds aloft at 10kft MSL: WSW around 10 kt.

KBOI...VFR with mid/high clouds, then visibility reductions due to wildfire smoke overnight into early Thursday. High density altitude Thursday afternoon. Showers and thunderstorms possible between 22Z Thursday and 03Z Friday. Surface winds: variable less than 10 kt overnight becoming WNW around 10 kt after 20Z.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Quality Alert until 2 PM MDT Friday for IDZ011-012-014-033. Fire Weather Watch from Friday afternoon through Saturday evening for IDZ401-402-423. Heat Advisory from 2 PM this afternoon to 9 PM MDT Saturday for IDZ012-014-016-033. OR...Air Quality Alert until 2 PM MDT /1 PM PDT/ Friday for ORZ061>064. Fire Weather Watch from Friday afternoon through Saturday evening for ORZ670>675. Heat Advisory from 2 PM MDT /1 PM PDT/ this afternoon to 9 PM MDT /8 PM PDT/ Saturday for ORZ063-064. Red Flag Warning from noon MDT /11 AM PDT/ today to 9 PM MDT /8 PM PDT/ this evening for ORZ673>675.