textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Warm with isolated thunderstorms near the ID/NV border through this evening.

- Gusty winds on Memorial Day ahead of a cold front, resulting in critical fire weather conditions in southeastern Oregon.

- Scattered showers/thunderstorms Monday PM resulting in strong outflows to 35-55 mph and blowing dust, mainly over SW Idaho.

- Much cooler with moderate wind and a chance of showers and thunderstorms Tuesday through Friday.

SHORT TERM /Through Tuesday Night/

Issued 224 PM MDT SUN MAY 24 2026 Warm and dry conditions continue through Monday, with temperatures 10-15 degrees above normal and afternoon minimum RHs 10-30%. The hottest day will be Monday, Memorial Day, which warms up just before a cold frontal passage that night. The alignment of pre-frontal winds with hot and dry conditions has resulted in a critical fire weather pattern prompting the issuance of a Fire Weather Watch. Wind gusts 30-45 mph are possible across SE Oregon, and 25-30 mph across SW Idaho. Winds may cause blowing dust across the area, limiting visibility and reducing air quality. Today and tomorrow, thunderstorms and showers are possible along the ID/NV border and in Central Idaho mountains. Behind the cold front, temperatures cool to 5 degrees below normal on Tuesday and conditions remain breezy as the overall low pressure system slows over the region. Lower temperatures allow morning RHs to climb to near saturation in some mountain valleys, which could produce brief low clouds. Precipitation chances increase to 40-70% across the area Tuesday evening, generally increasing with elevation.

LONG TERM /Wednesday through Sunday/

Issued 224 PM MDT SUN MAY 24 2026 Continued strong agreement that the area of low pressure bringing unsettled conditions to the region will be cut-off to the south over Nevada Wednesday into Thursday. An approaching trough is then expected to draw the low northward across Idaho and into Montana Thursday Night and Friday. The proximity of this low will keep temperatures 10-15 degrees below normal, and cold air aloft along with moisture will make the perfect conditions for rounds of showers/thunderstorms. Storms will favor the afternoon hours, but enough instability will exist for activity throughout each day and even overnight. Storm total precipitation of 0.3-0.5 inches is forecast for lower valleys, with 0.75-1 inches forecast for mountain valleys and the higher peaks of central Idaho. The probability of 0.5 inches or more is 35-45% for the lower valleys, and the probability of 1 inch or more for the Idaho mountains is 50-60%. Nearly all ensemble guidance has the low east of the region by Sunday with improving conditions and slow warming trend anticipated.

AVIATION /00Z Monday through Tuesday/

Issued 615 PM MDT SUN MAY 24 2026

VFR. Showers/thunderstorms before 25/04Z near KTWF/KJER, capable of outflows up to 35 kt. Scattered showers/thunderstorms across SW Idaho and far NE Oregon Monday PM, producing outflows to 30-50 kt. Potential for blowing dust. Surface winds outside of storms: W-NW 5-15 kt this eve, then variable up to 12 kt overnight. Then, SE-SW 10-20 kt with gusts 15-35 kt after 25/16Z. Winds aloft at 10kft: WSW 10-25 kt, becoming SSW 20-30 kt Monday PM.

KBOI...VFR. Shower/thunderstorm threat between 25/20Z and 26/00Z. Storms will be capable of outflow winds to 35-45 kt, cloud to ground lightning, and blowing dust. Surface winds: NW 5-10 kt, becoming SE 5-12 kt after sunset.

FIRE WEATHER

Hot temperatures well above seasonal normals, minimum RHs 10-15%, and gusty winds 30-45 mph have prompted the issuance of a Fire Weather Watch in Southeast Oregon for Memorial Day afternoon and evening. A cold front, expected to arrive that night, will bring gusty pre-frontal winds within the already warm and dry environment. Scattered thunderstorms expected to develop across southwest Idaho Monday afternoon/evening could bring strong outflow wind gusts of 35-55 mph as well as lightning. This could effect ongoing wild and prescribed fires across the Western Twin Falls BLM, Boise BLM/NF and Payette NF. Morning maximum RHs consistently recover Wednesday morning through the rest of the week, with a 30-40% chance of wetting rain each day as the low pressure remains overhead.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...Fire Weather Watch from Monday afternoon through Monday evening for ORZ670-672.