Debris Flow in Ada County, Idaho

Debris Flow August 26, 2025 · Ada County, Idaho

Where the report was made, with tornadoes recorded within 15 miles over the years.

What the National Weather Service wrote

On the east side of the Valley Fire burn scar, heavy rainfall with a peak rain rate of 7 inches per hour caused a slurry of mud, ash, and debris to flow down eastern Highland Valley Rd, depositing nearly a foot of debris on the road with running water estimated at 12 inches high. The road would have been impassable while water was running, and the debris flow ran down the length of the valley. No impacts along Hwy 21.

The wider storm

Monsoonal moisture surged into the region over a three day period, the most intense of which was the 26th. High atmospheric moisture content combined with weak flow in a monsoonal pattern to produce very moist storms moving very slowly. Additionally, as terrain served as the main trigger for convection, storms would train over the same spots for much longer than normal. Precipitable water was at near record levels around 1.2 inches.

Began near Barber (43.5537, -116.0455).

Source: NOAA Storm Events Database, event 1295132. Narratives are written by the National Weather Service forecast office that issued the report.

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