textproduct: Boise

KEY MESSAGES

-Cold front will bring a cooling trend through Tuesday, with gusty northwest winds and chance of rain showers over valleys and snow showers over mountains.

-Weak system will continue precipitation and thunderstorm chances Tuesday, mainly over the southern portions of the area.

-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.

SHORT TERM /Through Tuesday Night/

A shift in the pattern will begin Monday with a cold front that will reach southeast Oregon early morning before tracking through the Treasure Valley by midday and exiting into the Magic Valley by Monday evening. This front will bring a notable cooling trend, with high temperatures dropping into the 50s and 60s. Precipitation with the frontal passage will be most concentrated over the mountains of east-central Oregon and west- central Idaho. While lower valleys may see a few light showers, measurable amounts are expected to be minimal. Breezy northwest winds will develop behind the front, with gusts of 25 to 35 mph possible.

Tuesday remains unsettled as a weak trailing shortwave tracks across the Great Basin. High-res models remain split on the track of the shortwave and associated precipitation, particularly along Monday's frontal boundary. Though confidence is low in the northern extent of the precipitation, this feature will steer a band of moisture resulting in a 25 to 60 percent chance of precipitation across the southern third of the region. While total liquid amounts will generally range from 0.05 to 0.25 inches, the introduction of cooler air aloft and weak instability will create an environment favorable for a few isolated thunderstorms during the afternoon and evening hours. Snow levels will rise between the 5000 to 7500 foot range Tuesday ahead of the next major system, with light accumulating snow of 1 to 2 inches possible above 6000 feet.

LONG TERM /Wednesday through Sunday/

The well advertised Gulf of Alaska low will swing down across the Pacific NW come Wednesday. This low will bring widespread precipitation across our area. Moisture transport in increasing southwesterly flow aloft will first bring precipitation across higher terrain; with flow at 700mb reaching 30-50kt, orographic lift will be the main player initially. The strongest forcing (and therefore the period of heaviest/most widespread precipitation) will come Wednesday night through Thursday, as the main trough and cold front moves across our area. With weak elevated instability and forcing along the front, convective enhancement will allow for locally heavier precipitation rates and a slight chance of thunder. Snow levels during this period will be between 6-4.5 kft MSL.

Come Thursday afternoon, the cold front will be east of our area with the core of the 500mb low nearly overhead (temperatures at 500mb will be near -32 degrees Celsius, within the 10th percentile of climatology). Gusty west-northwest post frontal winds will also set in Thursday. While cloud cover will likely reduce diurnal heating, these cold temps aloft when combined with diurnal heating will allow for weak instability to build in. This will allow for precipitation to take on a more showery nature, with rain, snow/graupel showers, and perhaps even some thunderstorms. Snow levels behind the front will drop to 3-4kft MSL, which will allow for mountain valleys to accumulate a couple inches of snow (50-70% chance). Over the course of Wednesday/Thursday, Liquid precipitation totals of 0.30-0.75 inches are forecast in lower elevations, with 0.75-1.5 inches of liquid over the mountains. Above 6500 feet, there is a 70+ percent chance of receiving over a foot of snow.

As the trough moves east out of our area through Friday and ridging begins to build back, precipitation chances will taper off and a warming trend will set in through Sunday.

AVIATION /18Z Sunday through Monday/

Issued 1208 AM MDT SUN MAR 29 2026

VFR today, a cold front Mon/AM will bring scattered rain/snow showers mainly north of a line from KBNO-KONO-KSNT. MVFR/IFR conditions in rain/snow showers with mtn obscuration. Snow levels: 7-9kft MSL, lowering to 2-4kft MSL behind the front. Surface winds: SW-W 5-15 kt. Gusts 20-35 kt across SE Oregon and higher terrain SW Idaho through 30/03Z. Becoming W-NW 5-15 kt with localized gusts to 20 kt Mon/AM. Winds aloft at 10kft MSL: W-SW 20-35 kt.

KBOI...VFR. Surface winds: Generally light and variable, with periods of W-SW winds up to 10kt possible this afternoon. Becoming W-NW 5-10 kt overnight tonight.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.