textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- A cold frontal passage Saturday will bring cooler temperatures, light mountain showers, and gusty W-NW winds through the evening.

- Warm, slightly above normal temperatures will continue the middle of next week.

- Another cold front will move through the region by the middle of next week, bringing mountain showers and cooler temperatures.

SHORT TERM /Through Monday Night/

Issued 224 PM MDT SAT MAR 21 2026 A weak cold front is continuing to push southeastward across the forecast area this evening. While the front is not well defined in surface observations, it is clearly demarcated by a developing cumulus field on satellite imagery. The primary impact has been elevated winds this afternoon and evening, with wind gusts reaching up to 40 mph in wind-prone areas. Precipitation chances remain low as the deepest moisture stays to our north, though a 10 to 20 percent chance of light rain showers will continue for northern portions of Baker and Valley counties through tonight.

The ridge begins to build back over the area on Sunday. This will shift the cooler zonal flow further north, keeping our region dry. Temperatures will remain above normal through the period. By Monday night, an atmospheric river associated with a low off the British Columbia coast will begin to approach the Pacific Northwest. While this system will attempt to push moisture and colder air into the region, it will face resistance from the persistent ridge over the Desert Southwest. Guidance today continues to trend warmer and drier; consequently, any precipitation through Monday night is expected to remain light and confined mostly to the higher terrain of Baker County and the mountains of southwest Idaho.

LONG TERM /Tuesday through Saturday/

Issued 224 PM MDT SAT MAR 21 2026 The large upper level ridge over western US the will flatten out a bit allowing a more zonal west to east upper level flow to bring moisture into the area on Tuesday and Wednesday. The best chances for precipitation will be across the northern half of our forecast area where a 50 to 60 percent chance of rain exists. The southern half of the forecast area will remain dry. The zonal flow pattern should allow temperatures to cool down a bit Wednesday through Thursday, though still remaining above 5 to 10 degrees above normal. Most models show the ridge beginning to rebuild over the western US again by Friday and continue that pattern into the weekend. The forecast for southwestern Idaho and southeastern Oregon responds to that scenario and shows a warming trend starting on Friday with dry weather.

AVIATION /06Z Sunday through Monday/

Issued 1120 PM MDT SAT MAR 21 2026 VFR conditions with scattered high cloud coverage overnight. Winds will be NW 10 kt or less overnight through Sunday morning, except 10-15 kt with gusts to 25 kt over KMUO, KTWF, and KJER. Winds aloft at 10K feet: W 30-40 kt.

KBOI...VFR. Surface winds W-NW 10 kt or less overnight through the afternoon.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.