textproduct: Boise

KEY MESSAGES

- Cool and breezy this weekend, temperatures 10 to 15 degrees below normal.

- Mountain rain and snow showers today and Sunday with light snow accumulations at higher elevations.

- Patchy frost possible Monday morning mainly east of Mountain Home.

SHORT TERM /Through Monday Night/

An upper level trough and associated cold front will continue to push across southeast Oregon and southwest Idaho today. The primary impacts with this initial passage will be gusty winds, generally 20 to 30 mph with gusts to 40 mph, across much of the area alongside a mix of rain and snow showers across Baker County and the West Central Mountains of Idaho. Snow levels will drop quickly behind the front to around 4000 feet, leading to light snow accumulations of a few tenths of an inch above 5500 feet.

Tonight into Sunday, the core of the upper level low moves directly over the forecast area, bringing a reinforcing shot of unseasonably cold temperatures. While moisture becomes limited, cold air aloft will keep the atmosphere unstable enough to generate scattered, light snow showers. This activity will be focused over parts of southeast Oregon and along the Idaho/Nevada border. Northwest winds will remain elevated and gusty through the night into Sunday afternoon. By Sunday evening, the low pressure system begins to exit to the east, but a tight surface pressure gradient will maintain breezy northwest winds throughout the day. Dry air will steadily filter into the region, resulting in a clearing trend from north to south.

As the upper ridge builds in on Monday, ideal conditions for radiational cooling will develop under clear skies and diminishing winds early Monday morning. This will lead to a very chilly morning, with temperatures dropping near or below freezing in several locations. There is a strong possibility of patchy frost across the agricultural areas of the western Magic Valley around daybreak. Monday afternoon will see a nice recovery with plenty of sunshine and lighter winds as high pressure takes firm control through Monday night.

LONG TERM /Tuesday through Saturday/

An upper level trough will begin to exit the region on Tuesday, keeping the area in northwesterly flow. Showers will linger on Tuesday into Wednesday over high terrain in southwest Idaho, with temperatures near normal through Wednesday. Model uncertainty increases on Thursday, with some models strengthening a low pressure system over the region and bringing a push of cool air with another shot of moisture on Thursday and Friday. Others bring hot and dry conditions thanks to a building ridge of high pressure beginning as early as Wednesday. Current forecast favors the warmer and drier trend. By Saturday, high confidence exists in warm and dry conditions either continuing or returning with the ridge more firmly in place through the weekend. Therefore, above normal temperatures are likely Wednesday-Saturday.

AVIATION /06Z Saturday through Sunday/

Issued 1217 AM MDT SAT MAY 16 2026

VFR. Cold front moving into SW ID after Sat/08Z. Increasing NW winds and scattered rain/snow showers north of KBNO-KONO-KSUN tonight through Saturday night. Snow levels 4.5-6kft by mid-morning. Local MVFR/IFR in showers with mtn obscuration. Surface winds: W-NW 5-15 kt with 20-25 kt gusts, by Saturday afternoon NW 10-25 kt winds with 25-40 kt gusts. Winds aloft at 10kft MSL: W 15-30 kt.

KBOI...VFR. Cold frontal passage around 16/08z, bringing increased NW winds and mid-level ceilings. Surface winds: NW 10-20 kt with gusts to 25-30 kt Saturday.

Sunday Outlook: Rain/snow showers expanding southward Sat night through mid-day Sunday, favoring SE Oregon, ID-NV border, and central ID mtns. Periods of IFR-LIFR and in mountain snow/low ceilings. Mtns obscured. Snow levels drop to 3-5kft MSL by early Sunday AM. Surface winds: NW 10-25 kt with gusts 25-40 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.