Afternoon thunderstorms rolling off the Wasatch Front through the weekend could send runoff rushing out of Big Cottonwood and Little Cottonwood canyons, putting nearby Cottonwood Heights and Holladay neighborhoods on alert for localized flash flooding.

The Weather Prediction Center on Wednesday, July 15, issued a marginal, or 5%, risk of flash flooding within a 25-mile radius for most of Utah, including the Salt Lake Valley. For Thursday, July 16, the WPC maintained that 5% marginal risk for central and northern Utah while elevating the risk to 15% for southern Utah, according to ABC4 Utah meteorologist Cedric Haynes.

The 5% marginal risk is the WPC's lowest flash flood category. No specific flash flood watch or warning has been issued for Salt Lake County.

Still, the threat is real near dry washes and canyon mouths where steep terrain concentrates runoff quickly during heavy downpours. Cottonwood Heights and Holladay sit directly at the base of two major Wasatch canyons, and brief, intense storms can push water and debris into low-lying areas with little warning.

No burn scar exists in or near Big Cottonwood or Little Cottonwood canyons. The Cottonwood Fire burn scar, where minor flooding occurred on Tuesday, July 14, is in Beaver County, roughly 200 miles to the southwest. NWS meteorologists have warned that burn-scarred areas elsewhere in Utah face much lower flooding thresholds, but the local risk here is from general monsoon runoff, not fire-damaged terrain.

A ridge of high pressure east of Utah is driving a southerly flow that pulls monsoonal moisture northward. Scattered showers and thunderstorms developed across Utah on Tuesday, July 14, and the pattern is forecast to intensify, with the greatest thunderstorm chances running Thursday through Saturday, July 18, according to ABC4. Daytime highs in the Salt Lake Valley will stay in the mid- to upper 90s through the weekend, with overnight lows in the low to mid-70s.

Long-range guidance as of Wednesday, July 15, indicates the monsoonal pattern will continue through the middle and end of the following week.

Haynes urged anyone who encounters flooded roadways to turn around immediately, noting that just a few inches of moving water can sweep a person off their feet.

Residents near canyon mouths and low-lying washes can sign up for Salt Lake County emergency alerts through the county's emergency management office or call 911 to report active flooding.