A second surge of tropical moisture could bring flash-flood conditions back to the Wasatch Front, including Millcreek, as early as Friday, Sept. 4, according to ABC4 meteorologist Cedric Haynes.

The warning comes one day after heavy rain and flash flooding hit Utah on Monday, Aug. 31. Conditions are forecast to dry out Tuesday, Sept. 1, through Thursday, Sept. 3, but the break will be short-lived.

As we reported Aug. 31, the Salt Lake City area carried a "Slight," or 15%, risk of flash flooding within 25 miles that day. In his Aug. 31 forecast, Haynes wrote that forecasters are closely watching a potential eastern Pacific tropical cyclone that could funnel tropical moisture into Utah. He said many weather models are in "decent agreement" that the moisture will arrive and bring another round of elevated flooding, with the best chances falling Friday, Sept. 4, through Sunday, Sept. 6, and possibly extending into the week of Sept. 7.

The forecast is not yet locked in.

No National Weather Service watch or warning has been issued for the Millcreek area covering the Sept. 4 through Sept. 6 window as of Sept. 1.

Monday's damage statewide

The storms that hit Utah on Aug. 31 showed what saturated ground and tropical moisture can do. Flash flooding struck Zion National Park shortly after 1:30 p.m., according to KSL. A gauge at the North Fork of the Virgin River at Springdale spiked to 5,920 cubic feet per second (cfs), up from a normal flow of about 35 cfs. That was the gauge's fifth-highest peak on record.

KSL meteorologist Matt Johnson explained the mechanism behind the storms: tropical, monsoonal moisture fused with a low-pressure system over Arizona and moved north into Utah, where it merged with another low-pressure system from California.

"(When) you clash low pressure and tropical moisture, you're getting activity," Johnson said.

The National Weather Service had issued a moderate risk, Level 3 out of 4, for excessive rainfall in southeastern Utah on Aug. 31, according to the Deseret News. The highest risks that day extended from the Northern San Rafael Swell into the Uinta Basin.

What to watch for

In his Aug. 31 forecast, Haynes wrote that gusty southerly winds are expected to continue through Sunday, Sept. 6, and into the week of Sept. 7, with the strongest gusts likely along the Wasatch Front. The return of cloud cover and moisture from the second tropical surge could push daytime highs slightly below average.