textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

-Valley rain and mountain snow through Tuesday. Breezy northwest winds in the daytime will gust up to 30 mph and afternoon thunderstorms are possible on Tuesday.

-The most impactful system arrives late Wednesday, bringing gusty winds and heavy mountain snow into Thursday. Heavy wet snow is expected above 6000 feet, potentially resulting in slushy or snow-covered conditions on Highway 55, Highway 21 and US 95 Thursday morning.

-Dry weather and above normal temperatures return for the weekend.

SHORT TERM /Through Wednesday Night/

Issued 209 PM MDT MON MAR 30 2026 A weak cold front continues to move southward across the forecast area this afternoon and evening. This will maintain scattered showers across much of the area. Light snow accumulation has already occurred above 6000 feet, and further accumulation is possible in mountain valleys this evening. However, this will be limited to colder surfaces, while sites in Valley County above 6000 to 6500 feet MSL will pick up 1 to 2 inches. Breezy northwest winds of 15 to 25 mph with gusts to 30 mph will continue into the evening as the front reaches the Nevada border. A shower or two is possible (10 percent chance) for the Treasure Valley, but little to no measurable precipitation is expected.

A second wave will push into the region on Tuesday, bringing another round of showers. Most high-res guidance has come into agreement regarding a period of light to moderate precipitation ahead of the trough Tuesday morning. This will be focused along a warm front shifting northward across the area. Showers and thunderstorms are then expected to develop in the unstable air on the back end of the trough Tuesday afternoon and evening. Most areas have a 60 to 80 percent chance for measurable precipitation, with a broad area of 0.05 to 0.15 inch amounts through Tuesday evening. Locally higher amounts are possible, especially along the frontal boundary. Southwest flow ahead of this wave will raise snow levels to 6500 to 7500 feet.

The main upper level low will move into the Pacific Northwest on Wednesday. This is when precipitation becomes widespread across the region, especially Wednesday night. Gusty southwest winds ahead of the system will reach 20 to 30 mph with gusts of 35 to 45 mph across southeast Oregon and the higher terrain of southwest Idaho, mostly south of the Snake Plain. The mild and moist airmass along with the favorable upper level dynamics, supports a chance of thunderstorms. Snow levels will hold around 6500 feet MSL during the day, dropping to between 4500 to 6000 feet overnight as colder air moves in aloft behind the cold front. This is when the heaviest snow (8 to 16 inches) will occur above 6500 feet, impacting higher roadways across Banner Summit, Big Creek Summit, and Warm Lake Summit. Mountain valleys will see accumulations (3 to 6 inches) as rain changes to snow Wednesday night and early Thursday morning with the frontal passage. Parts of state highway 55 and US 95 could become slushy or snow covered Thursday morning. Widespread precipitation amounts of 0.20 to 0.50 inches are expected across lower elevations, with 0.50 to 1.00 inch in the mountains through Wednesday night.

LONG TERM /Thursday through Monday/

Issued 209 PM MDT MON MAR 30 2026 Widespread precipitation will continue Thursday as the upper level low continues to infringe upon our area. By Thursday afternoon, this low will be centered over E-Oregon/SW-Idaho. With the cold core over our area, weak instability will be able to build in through diurnal heading (although cloud cover will help reduce the amount of destabilization). As a result, precipitation will take on a showery nature with rain, snow/graupel, and perhaps even a thunderstorm Thursday afternoon. With the cold front east of our area come Thursday afternoon, windy west/northwest post-frontal winds will also set in. The strongest winds will be in the typical locations, with gusts to 35-50 mph in the Snake Plain east of Mountain Home, Camas Prairie, and along ridge tops. elsewhere, winds will gusts to 20-35mph (barring sheltered mountain valleys).

As the system exits our area to the east through Friday, precipitation chances will begin to taper off with scattered showers continuing over higher terrain. Come Saturday, dry conditions will prevail with a warming trend setting in as ridging begins to build back in behind the trough. By Sunday, temperatures will be up to 5-10 degrees above normal. Ensemble and deterministic guidance hint at a shortwave grazing our area to the north come Monday afternoon, leading to a slight chance of showers over the terrain in our northern zones.

AVIATION /00Z Tuesday through Wednesday/

Issued 552 PM MDT MON MAR 30 2026

Showers increasing tonight into Tuesday in all areas along a frontal boundary. Mainly low VFR or MVFR in rain, with MVFR/IFR in the mountains. Mountains obscured. Snow levels: 4-6kft MSL across the north, 6-7kft MSL central and south. Isolated thunderstorms developing Tuesday afternoon with gusts up to 35 kt and small hail possible. Surface winds: W-NW 5-15 kt, becoming variable less than 10 kt overnight. Winds Tuesday SW-NW 5-15 kt, with gusts 20-30 kt over the higher terrain and SW of the Snake Basin. Winds aloft at 10kft MSL: W-SW 20-35 kt.

KBOI...Mainly VFR. A 30% chance of rain showers this evening. Steady rain developing overnight into Tuesday morning, bringing a 30% chance of MVFR ceilings. A 15% chance of a thunderstorm after Tue/20z. Surface winds: NW 5-15 kt, becoming SE less than 10 kt overnight.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.