textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Hot with widespread wildfire smoke persisting across southeast Oregon and much of southwest Idaho through today.

- Dry cold front this evening will bring period of critical fire weather conditions and gusty winds.

- Remaining dry but not as hot Sunday through Tuesday. The heat returns by midweek.

SHORT TERM /Through Monday Night/

Issued 332 AM MDT SAT AUG 1 2026 Per water vapor satellite imagery, an upper-level low is sitting just off the British Columbia coast, and will move onshore over the course of today. This is contrasted with the strong upper-level ridge over the Desert Southwest, which will continue hot and dry conditions for the region today. Temperatures will again touch 100 degrees at lower elevations, with locally hotter temperatures (Mountain Home to Hagerman) pushing 100-105 degrees. Flow aloft will increase out of the southwest as the pressure gradient between the trough and ridge increases through the day. The hot diurnal temperatures will promote strong vertical mixing, causing the gusty winds aloft to mix to the surface. Higher, open terrain in SE Oregon and SW Idaho will tap into the southwest winds, bringing gusts to 30 mph by afternoon. Additionally, a dry cold front from the upper-level trough moving across the southern Canadian provinces will move into SE Oregon by late afternoon, advancing into SW Idaho during the evening. Winds gusts will be strongest across SE Oregon, especially along the I-84 corridor between Baker City and Ontario where gusts to 45 mph are expected into tonight. With these increased wind speeds throughout the day, alongside ongoing wildfires and low minimum relative humidities, Red Flag Warnings are in effect this afternoon into evening. Additionally, Baker County is under a Wind Advisory as relative humidities increase in the evening hours with gusty winds continuing. Elsewhere, wind gusts top out between 25 and 40 mph across SE Oregon and the Snake Plain/Highlands of SW Idaho through Saturday night as the front moves through.

Sunday will be a considerable change of pace, with the post frontal air mass high temperatures 10-15 degrees cooler than today. The region will also become considerably drier starting Sunday, with PWAT values falling beneath the 10th percentile (near 0.3 inches). Additionally, breezy winds will persist as westerly flow aloft channels through the terrain, particularly from Mountain Home through the Western Magic Valley. From all of these factors, elevated fire weather concerns remain. Forecast models are cutting down on smoke coverage for Sunday as westerly flow in a well mixed environment vents out the smoke that has pooled up over the last week(ish) and modeled plumes from ongoing fires are tighter. Do expect some improvement going into early next week, but uncertain on how much, especially if there are new starts or Saturday's wind/RH event kicks up current activity. Sunday night will be cool compared to the recent past with temperatures dropping below 60 across the Snake Plain. Officially for Boise this would be the first sub-60 degree temperature since July 3rd. Monday will continue the trends from Sunday, with cooler (but still warm) temperatures, breezy afternoon winds, and dry.

LONG TERM /Tuesday through Saturday/

Issued 332 AM MDT SAT AUG 1 2026 The Desert Southwest upper-level ridge will be, yet again, driving the synoptic pattern. Clusters have the extent of the highest 500 mb heights associated with the ridge reaching to the California coast, thereby limiting any monsoonal moisture from getting north to our region. Thus, hot and dry conditions are expected to return and stick around. By Wednesday, highs are back into the mid-upper 90s/near 100 degrees across lower elevations (smoke coverage/density dependent). There is no chance for precipitation through the period as monsoonal moisture remains bottled up over the Four Corners region.

AVIATION /12Z Saturday through Sunday/

Issued 524 AM MDT SAT AUG 1 2026

Wildfire smoke creating low VFR/MVFR visibility through this evening, with mtn obscurations. Local IFR across E Oregon and along the OR/ID border. Hot temps creating high density altitude this afternoon. Surface winds: variable under 10 kt, increasing to SW-NW 5-15 kt with gusts 15-25 kt Sat afternoon. Then, W-NW 10-20 kt with 25-45 kt gusts with cold front Sat night. Winds aloft at 10kft MSL: SW 10-25 kt.

KBOI...Low VFR visibility in smoke, with potential for MVFR visibility returning Saturday afternoon through early evening. Improving conditions Saturday night with gusty cold front. Surface winds: light variable/SE around 5 kt overnight, then NW 5-15 kt by late Sat morning and afternoon.

Sunday Outlook...Gusty W-NW surface winds 15-25 kt. Wildfire smoke is expected to mix out of most areas with the elevated wind speeds, but visibility reductions still expected near wildfires.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Air Quality Alert until 2 PM MDT Monday for IDZ011-012-014-015- 029-033. Red Flag Warning from 3 PM this afternoon to 9 PM MDT this evening for IDZ400-402-423. OR...Red Flag Warning from 3 PM MDT /2 PM PDT/ this afternoon to 9 PM MDT /8 PM PDT/ this evening for ORZ670>675. Air Quality Alert until 3 PM MDT /2 PM PDT/ Monday for ORZ061>064. Wind Advisory from 8 PM this evening to 2 AM PDT Sunday for ORZ062.