textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Dry weather with warming temperatures through Sunday.

- Cooler Monday and Tuesday with gusty winds and an increased chance of showers and high mountain snow.

- Gulf of AK low will bring widespread precipitation Wednesday and Thursday. Accumulating snow is possible down to mountain valley floors with heavy snow possible above 6500 feet.

SHORT TERM /Through Sunday Night/

Issued 207 PM MDT FRI MAR 27 2026 Upper level ridging will remain the dominant feature across southeast Oregon and southwest Idaho through the weekend. This ridge will maintain dry conditions and promote a significant warming trend, with temperatures reaching 10 to 15 degrees above seasonal normals. With the ridge keeping the atmosphere dry at the lower levels, a weak impulse moving across central Nevada will bring an increase in high cloud cover on Saturday. Despite the filtered sunshine, afternoon highs will continue to climb, generally warming 3 to 8 degrees over Friday's values. Low level easterly winds will persist, particularly across the Snake River Plain, though speeds are expected to remain below any advisory thresholds.

By Sunday, the ridge begins to flatten in response to an approaching upper level trough from the Gulf of Alaska. This will result in a mix of sun and clouds throughout the day. Temperatures will stay steady at their peak, remaining well above normal for late March. Sunday night, as the trough draws closer, cloud cover increases along with a slight chance for showers (15-20%) across the east-central Oregon and west-central Idaho mountains, specifically north of a Baker City to McCall line.

LONG TERM /Monday through Friday/

Issued 207 PM MDT FRI MAR 27 2026 A spring pattern will manifest come next week. The first glimpse of this pattern will be in the form of a cold front late Monday into early Tuesday. Temperatures on Monday will depend on the timing of this frontal passage, with above normal temperatures ahead of it and near to below normal temperatures behind it. This frontal passage will also offer our first chances of precipitation as it passes. Monday afternoon, precipitation chances will increase to 30-65% (highest in the central Idaho mountains) through early Tuesday morning. There is some uncertainty regarding precipitation chances Tuesday through Wednesday, as zonal flow may allow for the passage of shortwaves in the main flow aloft. Ensemble Guidance is backing off on precipitation for Tuesday, but am maintaining a slight chance to chance of precipitation to account for uncertainty.

Confidence increases regarding the next system to come mid- week. Wednesday into Thursday, a Gulf of Alaska low will dig down across the area. This will offer up the best chance of precipitation area-wide and bring below normal temperatures behind a cold front. Precipitation chances will increase through Wednesday, reaching 60-90% area-wide by late Wednesday night through Thursday. Wednesday afternoon will also support the best chance for a thunderstorm, with ensemble guidance building in weak instability as cooling aloft steepens lapse rates. Uncertainty remains regarding the speed of the system this far out (and therefore its residence time over us). However, precipitation will take on a showery nature, with cool air aloft plus diurnal heating, and taper off late next week. This cool system will lower snow levels and offer up a chance for our mountains to get some late season snow. Snow levels Thursday will drop to 2.5-4.5kft MSL and hover there through Friday (with the lower bound of that range coming overnight Thursday). Wednesday through Friday, the chance of at least a foot of snow ranges from 40-80% for peaks above 6500 ft MSL. Mountain valleys may even pick up a few inches of snow over the same period. Winds will be breezy to gusty each day.

AVIATION /00Z Saturday through Sunday/

Issued 609 PM MDT FRI MAR 27 2026

VFR under increasing high clouds. Surface winds: variable 12 kt or less overnight, becoming SW-NW 5-15 kt Saturday afternoon, with gusts 20-30 kt across higher terrain. Winds aloft at 10kft MSL: SW 10-25 kt.

KBOI...VFR. Surface winds: SE up to 8 kt overnight, becoming NW 4-8 kt Saturday afternoon.

Sunday Outlook...Mainly VFR under mid to high clouds. Lower clouds with light showers across the northern mountains in the afternoon and evening. Breezy SW-W winds with gusts 20-35 kt in the afternoon across higher terrain, otherwise variable surface winds less than 12 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.