textproduct: Boise

KEY MESSAGES

- Showers and thunderstorms through Sunday. Strongest storms Friday afternoon, bringing gusty winds, hail, and heavy rain.

- Dry and mild Tuesday.

- Cooler temperatures with periods of precipitation through Wednesday through Friday.

SHORT TERM /Through Sunday Night/

An active day is in store Friday. As a Gulf of Alaska low digs down off the California coast, a shortwave embedded in southerly flow aloft will cross over our area. This will allow for scattered thunderstorms to develop Saturday afternoon. Cooling aloft associated with the shortwave and diurnal heating will allow MU CAPE values of 500+ J/kg. The instability, paired with 0-6km shear of 40-50 kt and steep mid-level lapse rates, will support strong to severe thunderstorms. The best overlap of these variables will be over Owyhee (ID) and Malheur(OR) Counties, although instability will support thunder chances area-wide. Storms will move south to north through the afternoon, with the primary hazards being strong winds, hail, and heavy rain. The threat of thunderstorms will linger into overnight hours over the West Central Mountains with model soundings keeping elevated instability.

Showers will continue Saturday through Saturday evening as the low continues to move inland and another shortwave crosses our area. Cooler surface temperatures (lower valley temperatures in the 60s) will limit the amount of destabilization. However, cooling aloft associated with the passing shortwave will allow weak instability to develop. The greatest threat for thunderstorms Saturday afternoon will come roughly east of a line from Baker City, OR through the Owyhee mountains.

The unsettled pattern continues Sunday, as the main low continues to move inland. Despite surface temperatures cooling yet again, colder air advecting in aloft will continue to compensate for the reduced heat at the surface. This will lead to another 10-25% chance of thunderstorms across much of our area. These will be weaker in nature and embedded within stratiform showers; however, gusty winds, small hail, and heavy rain will be the primary threat. Precipitation chances will be 80+ percent come Sunday afternoon. Precipitation associated with this low and its progression over our area (Sunday through Monday), is currently forecast to range from 0.5-1 inch across E-Oregon (up to 1.5-2 inches over the Steens Mountain), and 0.25-0.5 inches across SW Idaho (up to 1-1.5 inches over the Owyhees and higher peaks of the central Idaho mountains). Locations above 6500 feet MSL in the central Idaho mountains will see 2-8 inches of snow over the same time frame. This precipitation will lead to rises in rivers and streams.

LONG TERM /Monday through Friday/

The unsettled pattern will continue through the long-term, as the trough continues to move inland over our area. Precipitation chances Monday will remain elevated at a 40-90% chance, highest over terrain. See the short term discussion for precipitation amounts. Temperatures on Monday will drop to below normal with a cold frontal passage. As the trough exits to the east, precipitation chances will taper off come Tuesday. Guidance is in good agreement on another trough digging down from the Gulf of Alaska and crossing over our area. This will lead to another period of increased precipitation chances across the area. Precipitation will taper off again Thursday behind the trough and associated cold front. Persistent northwest flow aloft and multiple cold fronts will keep temperatures leaning below normal throughout the long-term period.

AVIATION /06Z Friday through Saturday/

Issued 1141 PM MDT THU APR 9 2026

VFR. Scattered showers will continue over SE OR, OR/NV border, and Treasure Valley overnight through early morning. Widespread showers and scattered thunderstorms with gusty outflow winds and small hail expected Fri/PM. Surface winds: light and variable under 7 kt overnight, then SW-NW 5-10 kt in the afternoon. Winds aloft at 10 kft MSL: W-SW 10-25 kt.

KBOI...VFR with high clouds and light showers from south. Scattered thunderstorms (30-40% chance) expected Fri/PM. Thunderstorms capable of gusty outflows and small hail. Surface winds: SE under 7 kt, becoming NW 8-12 kt Fri/PM.

Weekend Outlook...Showers and thunderstorms will persist across the area 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 mtn snow are expected. MVFR/IFR conditions possible in precipitation with mountain obscuration. Snow levels 6500-8000 feet Saturday, lowering to 5000-6500 on Sunday. Surface winds: SW-SE 5-10 kt Saturday and W-SW 10-15 kt Sunday with afternoon gusts to 30 kt both days.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.