textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Above normal temperatures through Friday, with a cooler and wetter trend beginning Saturday. - Scattered showers with isolated strong thunderstorms Friday afternoon through Saturday, with gusty outflows, small hail, and brief heavy rain.

- Cooler with intermittent heavy rain and mountain snow Sunday through Tuesday.

SHORT TERM /Through Saturday Night/

Issued 302 AM MDT THU APR 9 2026 Southerly flow aloft will continue warm, above normal temperatures today and tomorrow. Moisture will push in from a strong offshore low on Thursday, bringing a slight chance of showers and thunderstorms southwest of the Snake River Valley over southeast Oregon and the Idaho-Nevada border this afternoon. This low will then move onshore early Friday, bringing widespread showers and thunderstorms, with significant instability over the region. Southerly flow will aid in increasing instability throughout the region, increasing the chance of thunderstorms (15-30% chance) overnight on Friday through Saturday. The coastal low will then weaken as it moves into northern California with another low moving quickly onshore, bringing much cooler and wetter weather to the area late Saturday. Current model forecasts show Friday afternoon through Saturday afternoon as the peak time for thunderstorm formation over the entire region. Gusty outflow winds, lightning, and small hail will accompany any stronger storms that form on Friday and Saturday. Most storms look to be sub- severe, but a few severe storms could form thanks to high instability/moderate shear over the area, especially in the Owyhee Mountains and over the Magic Valley on Friday evening. Rainfall totals through Saturday night will total over an inch of precipitation over higher terrain, with anywhere from 0.50-1.00 inch over valleys.

LONG TERM /Sunday through Thursday/

Issued 302 AM MDT THU APR 9 2026 The center of the dominant low pressure system will move from Northern California into our region on Sunday, bringing a cool and wet pattern through late Tuesday. Snow levels look to drop to 4000-5000 feet late Sunday and again on Monday night, with minor snow accumulations anticipated over high elevations in the southwest Idaho mountains. Breezy winds with gusts to 40 mph will occur over areas south of the Treasure Valley on Sunday as the offshore low moves inland. Below normal temperatures will occur on Sunday-Tuesday, with valley highs only reaching the mid to upper 50s. Variations in precipitation amounts exist through late Monday, thanks to different ensemble solutions' variability in positioning of the low. The low will then dive southeast by early Tuesday, bringing a brief return to mostly dry conditions on Wednesday. Showers will linger over high terrain on Wednesday, as another trough deepens into the region from British Columbia. This will bring much colder air and precipitation late Wednesday into Thursday. Model disagreement remains high on this system, with high uncertainty in timing and location of precipitation.

AVIATION /12Z Thursday through Friday/

Issued 540 AM MDT THU APR 9 2026

Mainly VFR with increasing mid to high clouds. Scattered showers and isolated thunderstorms developing this late this afternoon and evening along the Nevada border and SE Oregon, which may impact KBNO/KREO. Outflow gusts to 35 kt possible from storms. Surface winds: variable less than 10 kt this morning, then NW-NE 5-10 kt this afternoon. Winds aloft at 10 kft MSL: S-W 10-20 kt.

KBOI...VFR with increasing high clouds. Surface winds variable less than 8 kt this morning, then NW 5-10 kt in the afternoon.

Weekend Outlook...Showers and thunderstorms will increase across the area Friday and Saturday. Storms may be strong and produce heavy rain, small hail, and gusty winds. Thunderstorm chances will be more limited on Sunday, but widespread rain and snow is expected. MVFR/IFR conditions possible in precipitation with mountain obscuration. Snow levels 6500-8000 feet through Saturday, lowering to 5000-6500 on Sunday. Surface winds: SW-NW 5-15 kt Friday, W-SW 10-20 kt with afternoon gusts to 30 kt Saturday and Sunday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.