textproduct: Boise

KEY MESSAGES

- Isolated afternoon thunderstorms today and tomorrow with small hail, gusty outflow winds, and brief heavy rain.

- Slightly below normal temperatures with valley rain showers and mountain snow showers Sunday and Monday.

- Much cooler temperatures with periods of precipitation Wednesday through Friday.

SHORT TERM /Through Monday Night/

An active weather pattern remains in place as an upper level low continues to track through the Great Basin and Intermountain West Sunday and Monday. However, this afternoon and evening, the low remains off the California coast which is advecting warm moist air combined with weak surface instability for thunderstorm development. The most robust activity will occur this afternoon through early evening during peak heating. Main threats with these storms include gusty outflow winds up to 45 mph, small hail, and brief periods of heavy rain that could reduce visibility. Have seen storms produce up to 0.30 to 0.40 inches of rain in 30 minutes.

On Sunday, the center of the low pressure system moves directly overhead. This will result in widespread rain showers and mountain snow showers. The heaviest precipitation will occur through Sunday morning across the area as the low moves in. While instability will be slightly lower than today due to cooler surface temperatures, there is still enough energy for isolated thunderstorms during the afternoon and evening hours. Any storms that develop on Sunday will likely be less intense than today but still capable of producing erratic winds and small hail. Snow levels will begin to lower, reaching 5500 to 7000 feet MSL by Sunday evening, which may lead to light snow accumulations on the higher peaks.

By Monday and Monday night, the low begins to shift slowly toward the Rockies. High precipitation chances (50 to 90 percent) remain for much of the area through Monday as wrap around moisture continues. However, the cooler air mass will significantly limit instability, making thunderstorm chances much more isolated compared to the weekend. Snow levels will continue their downward trend, potentially dropping to 4000 to 5000 feet by Monday night. Breezy conditions are expected to develop as the system exits, with temperatures remaining well below seasonal normals.

LONG TERM /Tuesday through Saturday/

Brief ridging Tuesday morning is quickly overcome by a strong Alaskan low. Winds pick up Tuesday evening as cloud cover increases. Precipitation begins Wednesday morning and lasts through Thursday. The bulk of the precipitation falls Wednesday afternoon, with an area wide 80-90% chance of precipitation. Forecast rainfall amounts range from 0.2- 0.4 inches in valleys, and 0.5-1 inches in mountains. Not all the precip will fall as rain. The 540's dm heights in the low bring snow levels from 5-6 kft MSL Wednesday to valley floors by Thursday morning. Mountains will receive 4-12 inches of snow before Thursday. Thursday, mountains and mountain valleys receive 1-4 inches of snow, with highlands and low elevation valleys receiving a dusting up to an inch. Breezy 20-30 mph gusts persist through Wednesday and Thursday. As the system moves eastward, slight ridging moves in Friday and Saturday leading into a warming and drying trend. Temperatures rise fom 15 degrees below normal up to near normal on Saturday.

AVIATION /18Z Saturday through Sunday/

Issued 1202 PM MDT SAT APR 11 2026 VFR with broken cumulus as showers and isolated thunderstorms develop this afternoon. Strong showers and thunderstorms may produce outflow gusts up to 35 kt, small hail, and moderate- heavy rainfall. Showers and storms dissipate this evening. Snow levels this afternoon are at 6500-7500 ft MSL, lowing to 5500-6500 ft MSL tomorrow morning. Surface winds: SW-NW 5-15 kt with afternoon gusts to 20 kt. Winds aloft at 10 kft MSL: SW 10-20 kt.

KBOI...Generally VFR. Periodic rain showers today with a 20% chance of thunderstorms this evening. Brief clearing tonight before widespread rain moves in tomorrow morning. Surface winds outside of showers: SE 5-8 kt.

Sunday Outlook...Numerous rain/snow showers through the day Sunday. In the afternoon, there is a 10-20% chance of lightning with gusty winds. MVFR-IFR conditions in heavier precip. Mountain obscuration. Surface winds outside of storms: S-W 5-15 kt with PM gusts to 15-25 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.