textproduct: Boise

KEY MESSAGES

-Cooler with periods of 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.

-Strong Gulf of Alaska low will bring widespread precipitation and a slight chance for thunderstorms Wednesday and Thursday, with rain in the valleys and moderate to heavy snowfall over mountains.

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

SHORT TERM /Through Wednesday Night/

Cooler conditions will setup today into Tuesday as a series of upper troughs track across the region. The first system will pass to the north, pushing a cold front into the area later today. A band of rain and snow will develop over Baker County and the w-central Idaho mtns later this morning and be slow to move south through the day. Light snow accumulation is possible in mtn valleys through the morning, but will be limited to colder surfaces while sites in Valley County above 6-6.5kft MSL will pick up 1 to 3 inches. The front will usher in breezy northwest winds as it reaches the NV border by this evening. It's not a particularly strong front and precipitation coverage will decrease as it extends south. Wind gusts will top out around 30 mph behind the front.

A second wave will push into the region on Tuesday, bringing another round of showers. Current model timing would support a period of light-moderate precip ahead of the trough Monday night into Tuesday, with showers and thunderstorms developing in the unstable air on the backend of the trough Tuesday afternoon and evening. Most areas see a 60-80% chance for measurable precipitation with a broad area of 0.05-0.15" amounts through Tuesday evening. Locally higher amounts are likely but will be hard to pin down given the showery nature of the precipitation later in the day. The southwest flow ahead of this wave will raise snow levels to 6.5-7.5kft on Tuesday.

The main low, and most impactful weather system this week, will move into the Pac NW on Wednesday. Precipitation becomes widespread across the region by afternoon, and continues into Wednesday night. Gusty southwest winds ahead of the low will reach 20-30 mph with gusts of 35 to 45 mph across SE Oregon and higher terrain of SW Idaho (mostly south of the Snake Plain). The mild/moist air mass and favorable upper level conditions will support a chance of thunderstorms during the day. Snow levels will hold between 6-7kft MSL during the day, dropping to between 4500-6kft overnight as colder air moves in aloft. The heavier snow during this period will be above 6-6.5kft, impacting higher roadways across Banner Summit, Big Creek Summit, and Warm Lake Summit. Mountain valleys will see accumulations as rain changes to snow Wed night. Widespread precipitation amounts of 0.2-0.5" are expected across lower elevations with 0.50-1.00" in the mountains through Wednesday night.

LONG TERM /Thursday through Monday/

The area will remain under the jet exit region of the potent upper low digging across the northwest on Thursday. The 500 mb low core is expected to center over our CWA as it digs out East. Strong cold frontal passage associated with this low will sustain widespread valley rain, mountain snow, and gusty west- northwest winds Thursday. While dense cloud cover will likely reduce diurnal heating, the cold temps aloft from the low core will allow for weak instability to build in. This will allow for precipitation to take on a more showery/convective nature, with rain, snow/graupel showers, and even some thunderstorms Thursday afternoon. Snow levels behind the front will drop to 3-4kft MSL, which will allow for mountain valleys to accumulate a couple inches of snow and elevations above 6500 ft to accumulate up to a foot by late Thursday.

By Friday, the area will be under the backend of the low steering out east and be under northwest flow. A 30-50% chance of precipitation will continue over the mountains through Friday afternoon. Otherwise, ridging from a Pacific high will build back in Friday through the weekend, returning dry conditions and a warming trend with temperatures climbing 5-10 degrees above normal. Long- term guidance suggests another upper low steering inland from the Gulf of Alaska early next week, but with considerable guidance uncertainty over its pattern behavior and arrival. For now, mountain areas may see a 20-30% chance of precip on Monday.

AVIATION /06Z Monday through Tuesday/

Issued 1153 PM MDT SUN MAR 29 2026 Generally VFR. An incoming cold front will bring a rain/snow band with MVFR-IFR conditions over the east-central OR and west-central ID mountains after 10Z. MVFR-IFR conditions will persist over mountain areas through the afternoon. Mountains will be obscured at times. Surface winds W-NW less than 10 kt overnight, increasing to 10-20 kt after 16Z. Winds aloft at 10kft MSL: W-SW 20-35 kt.

KBOI...VFR. Increasing mid-level clouds with a stray shower possible in the morning after 14Z. Surface winds variable overnight, becoming NW 10-15 kt in the afternoon after 18Z.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.