textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Isolated showers and thunderstorms today. Stronger storms producing gusty winds possible in SW Idaho.

- Cool and dry Sunday then warmer early next week.

- A deeper low pressure system expected later next week for cooler, windier, and wetter conditions.

SHORT TERM /Through Monday Night/

Issued 201 PM MDT SAT AUG 29 2026 As an upper level low moves across the Pacific Northwest this afternoon, ahead of an associated cold front will support shower and thunderstorm development through the evening. Scattered showers will be capable of wind gusts up to 35 mph and light rainfall or virga. Embedded in showers, a few thunderstorms are possible and could produce wind gusts up to 50 mph and moderate rainfall. The chance of storms is about 10%, mostly north of the Nevada border and in mountains. While the chance of showers is 20% across much of Southwestern Idaho. At the same time as showers, southwesterly winds gust up to 25 mph.

The cold front proper moves through later this evening into the early overnight hours, bringing wind gusts up to 30 mph out of the northwest through Baker County, the I-84 corridor, and the Snake Plain. Wind gusts will be strongest in the I-84 corridor and following the Snake River. The airmass behind the front will make Sunday about 10 degrees cooler than Saturday and a bit drier with little to no chance of showers anywhere in the forecast area. Patchy frost possible Sunday and Monday morning across the higher valleys of southeast Oregon. Brief shortwave ridging on Monday will allow temperatures to rebound back toward normal levels, though shower chances will begin to return to south central Idaho late Monday night with the approach of the next upper level low pressure system.

LONG TERM /Tuesday through Saturday/

Issued 201 PM MDT SAT AUG 29 2026 Initial closed low off the Pac NW coast will open up and kick inland late Tue/Wed. This will bring a bump in precipitation chances, mostly across e-central Oregon and the w-central Idaho mtns. Warm and breezy conditions will precede this feature on Tuesday with temperatures 5-10 degrees above normal and gusts across open terrain approaching 30 mph.

Remainder of the forecast period will be dominated by a deep closed low that takes position along the OR/WA coast. There is consensus between deterministic solutions and ensemble mean to keep the closed low center to our west through Saturday. This puts our region under southwest flow as the low slowly fills. Looking at the details there are distinct forecast differences in size of the low and position it takes. Would put higher confidence on cooler/wetter conditions across SE Oregon zones for Thu-Sat. The ensemble mean paints 25-50% chance of precipitation during this period with a focus on Wed/Thur for the higher probabilities. For southwest Idaho zones, have higher confidence in cooler temps than seeing wetter conditions due to likelihood of a dry slot setting up between precipitation circling the low center and monsoon moisture further to our east. The w- central mtns would be most favored for precipitation Wed/Thur. Breezy/gusty winds can be expected through the period, especially during the afternoon/evening. Typically favorable spots for the strongest winds in this pattern are SE Oregon and higher terrain south of the Snake Plain. Starting Thursday temperatures will run about 10 degrees below normal (mid-upper 70s in Snake Plain).

AVIATION /00Z Sunday through Monday/

Issued 554 PM MDT SAT AUG 29 2026

VFR. Scattered showers and isolated thunderstorms this evening capable of 25-35 kt outflows, mainly southeast of a KREO-KBOI- KSNT line. SCT to BKN clouds in the same area, clearing out behind a cold front this evening. Surface winds: W-NW 5-15 kt with local gusts up to 30 kt following a cold frontal passage. Gusts decreasing overnight. Winds aloft at 10kft MSL: W-SW 15-30 kt

KBOI...VFR. Scattered showers and isolated thunderstorms to the south and east of the terminal this evening. A cold front arriving around 03z will bring a period of NW gusts up to 25 kt. Otherwise, surface winds will be NW 6-12 kt throughout the period.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.