textproduct: Boise

UPDATE

Updated aviation discussion and Key Messages

KEY MESSAGES

- Gusty afternoon winds Friday and especially Saturday, decreasing Sunday. - Very warm Friday, then cooler than normal Saturday through next Friday, warming next weekend.

- Showers mainly Wednesday through Friday with significant precipitation possible.

SHORT TERM /Through Saturday Night/

Issued 233 PM MDT THU JUN 4 2026 Zonal flow continues today as a trough off Haida Gwaii moves south along the BC coast today. As the trough moves south, the flow aloft shifts to the southwest, allowing for around 10 degrees of warming on Friday afternoon. This trough will move into WA on Friday afternoon, bringing a dry cold front through eastern OR on Friday evening. Gusty winds up to 35-45 mph possible Friday evening along the I-84 corridor from Baker City to Ontario OR as the cold front moves through. Winds elsewhere will not be fully realized as the cold front passes through during the overnight hours. The trough continues to move across WA on Saturday, with mostly cloudy skies. Showers and thunderstorms will generally be confined to areas north and east of our region, across eastern Idaho and the central ID panhandle. Dry and breezy conditions expected Saturday afternoon, with temperatures near normal or around 10-15 degrees cooler than Friday.

LONG TERM /Sunday through Thursday/

Issued 233 PM MDT THU JUN 4 2026 Showers in central Idaho move east Sunday as an upper level trough moves into western Montana. The showers bring a 10-20% chance of precipitation to the northeastern corner of Valley County, with a similar chance of thunder in the afternoon. As the trough moves out, much of Idaho sees gusty winds. Winds will be especially strong in south-central Idaho and parts of the Snake Plain between Boise and Twin falls. Gusts in these areas are forecast to be 25-35 mph. Afternoon maximum temperatures behind the trough will be about 5 degrees below normal.

Temperatures won't have much time to rise following the cool and breezy weekend, as models are in broad consensus bringing a strong trough through Idaho early next week. Models vary the most in the trough's amplitude, whether it closes and vorticity strengthens or remains a wave in the broader flow. This impacts forecasted precipitation coverage the most, but timing and placement is mostly consistent. Precipitation begins to move into southeast Oregon Monday evening, moves over all of southeast Oregon and southwest Idaho on Tuesday, and then southwest/central Idaho as it exits eastward Wednesday and Thursday. These areas see a 20-40% chance of precipitation, except on Tuesday where the core of the low bring a 50-70% chance of precipitation over mountains. Rainfall through the entire event is forecast to total up to 0.1 inches in lower elevations and up to 0.75 inches in mountains. Thunder is possible each day, especially Tuesday. A limiting factor of thunderstorms will be cooler surface temperatures with the low and cloud cover inhibiting instability. Thunderstorms could bring much higher local rainfall amounts to all elevations. The lower surface temps bring some snow to summits and ridgelines. Additionally, wind gusts increase in ridgelines and open areas during the low's passage. Each afternoon sees gusts 15 to 30 mph until Thursday where gusts in southeast Oregon weaken.

AVIATION /06Z Friday through Saturday/

Issued 1134 PM MDT THU JUN 4 2026 VFR with mostly clear skies. Dry cold front anticipated Friday afternoon across eastern Oregon, and then Friday evening and overnight across southwest Idaho. Surface winds: diurnal less than 10kt becoming SW-NW 10-20 kt with gusts to 25 kt by 20Z for Oregon sites and after 22Z in Idaho. Winds aloft at 10kft: W 20 kt becoming SW 20-25 kt after 05/20Z.

KBOI...VFR with a few high clouds. Surface winds: SE less than 10 kt becoming NW 8-12 kt after 05/19Z. Gusts to 25 kt after 06/06Z Saturday.

Weekend Outlook...VFR. Gusty west winds in the Snake Basin Saturday afternoon. Scattered rain and snow showers and local MVFR in northern mountains Sunday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.