textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated afternoon thunderstorms over southwest Idaho today with gusty outflow winds.

- Widespread valley rain and mountain snow above 4500 feet on Monday.

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

SHORT TERM /Through Tuesday Night/

Issued 204 PM MDT SUN APR 12 2026 An active weather pattern continues as an upper level low continues eastward across the Great Basin tonight. Increasing large-scale ascent and modest mid-level moisture associated with weak shortwave passage have combined with cold temperatures aloft and associated buoyancy for thunderstorm development this afternoon along the NV/ID border. These storms will support the threat for gusty outflow winds up to 45 mph and brief periods of heavy rain capable of reducing visibility as they push north- northeast across south-central Idaho. One or two storms could produce wind gusts near severe thresholds.

As the center of the low pressure system moves east-northeast across the region tonight, wraparound moisture and cooler northerly flow aloft will push a secondary band of precipitation starting across our northern zones early Monday morning. This band shifts slowly southeast as the low pushes eastward on Monday. This will bring much lower snow levels (4500-5500 feet MSL) and widespread precipitation to the region through Monday afternoon. Mountain valleys around 5000 feet could see 1-3 inches of wet snow, while mountain passes on US-95 and ID-21 could see up to 6 inches. High peaks over 8000 feet could see up to 12 inches of snow by Monday morning. Liquid totals from Sunday and Monday's periods of precipitation will reach 0.50-1.0 inches of rain north of the Treasure Valley, with locally higher amounts over high terrain.

By Monday night, the low is expected to exit toward the northern Rocky Mountains with breezy conditions and temperatures remaining well below seasonal normals. Brief ridging Tuesday will provide a short break before another strong Alaskan low approaches the region. Cloud cover will increase late Tuesday with precipitation beginning to spread into the southern mountains by Tuesday night.

LONG TERM /Wednesday through Sunday/

Issued 204 PM MDT SUN APR 12 2026 A strong low moves into the area on Wednesday, bringing rain, snow, and gusty winds through Thursday. Ahead of the colder airmass, snow levels begin at 5-6 kft MSL Wednesday. Rainfall during this time will total 0.1-0.4 inches in lower elevations, and 0.3-0.8 inches in higher elevations below 6kft. As snow levels drop to valley floors Wednesday night and Thursday morning, rain turns to mixed precipitation and snow. In lower elevations, snowfall will be a dusting up to an inch, in higher elevations 1-4 inches. Above 6kft, the storm total snowfall will be 4-12 inches, and up to 20 inches along ridges and summits in Central Idaho. As the cold front associated with the system moves through, temperatures drop from 5 degrees below normal on Wednesday, to 15 degrees below normal on Thursday. This cooling will put morning lows near to just below freezing in lower elevations Thursday through Saturday. Pre and post frontal winds Wed/Thu up to 35 mph are possible across the area.

Following this strong Alaskan low; warming and drying trend will set in beyond Thursday as ridging builds in across the area. Temperatures will return to near normal come Saturday, warming even more Sunday. The dry conditions don't appear to last too long, as another system will impact the area come early next week.

AVIATION /06Z Monday through Tuesday/

Issued 1123 PM MDT SUN APR 12 2026

Numerous showers producing low VFR to IFR conditions, becoming scattered late Mon afternoon. Periods of LIFR in mtn snow. Snow levels: 4500-5000 ft MSL through the AM, then 5500-6000 ft Monday PM. Mtns obscured. Surface winds: S-W 5-15 kt, then NW-W 5-15 kt with 20-25 kt gusts Monday PM. Winds aloft at 10kft MSL: W to NW 15- 30 kt.

KBOI...Rain returning around Mon/07Z, producing low VFR-MVFR conditions. Rain rates moderate/heavy at times. Showers becoming scattered late Mon afternoon. Slight chance of fog/low stratus Mon night/Tue AM. Surface winds: variable or SE 5-10 kt, transitioning to SW-NW 5-15 kt mid Monday morning.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.