Tropical moisture from Hurricane Polo pushed into the Wasatch Front on Monday, Sept. 28. The National Weather Service forecast an 80% chance of rain and scattered thunderstorms for the Bountiful, Woods Cross, North Salt Lake and Farmington area.

The NWS forecast for Bountiful called for showers through the afternoon with a high of 68°F. Overnight lows were expected to drop to 53°F with a continued chance of showers.

The storm system placed the Salt Lake-to-Ogden corridor, which includes Davis County, under what forecasters call a "Marginal" flash-flood risk, a 5% chance of flash flooding within 25 miles. The highest flood danger sat well to the south: a "Moderate" or 40% risk zone stretched from the Utah-Nevada border through Cedar City, Escalante and Moab, according to ABC4 meteorologist Cedric Haynes.

"This surge in moisture will lead to some of the highest flood concerns Utah has only seen one other time this year," Haynes wrote in his Monday forecast.

Flood watches covered central and southern Utah through Tuesday morning, with the southeast Utah watch extending through Tuesday night. The NWS posted a banner alert warning of heavy to excessive rainfall and possible flooding through Wednesday across the Southwest.

Heavy thunderstorms could not be ruled out along the Wasatch Front, Haynes reported, with more scattered storms along and south of Interstate 80. A cold front moving through the state kept conditions drier farther north, with only isolated chances near Cache Valley and the Idaho border.

An upper-level low pressure system diving across California and the Great Basin pulled southwesterly moisture from Hurricane Polo and Post-Tropical Cyclone Odalys into Utah. As of 8 a.m. Monday, the National Hurricane Center reported Polo was a Category 3 storm with 115 mph winds about 85 miles west-southwest of Cabo San Lazaro, Mexico, Newsweek reported.

For the Wasatch Front specifically, the KSL Weather outlook updated at 1 p.m. Monday placed the primary flash-flood threat from Juab County southward. The Salt Lake Valley zone forecast called for an 80% chance of rain Monday, dropping to 50% Monday night and 20% Tuesday afternoon.

Conditions should improve quickly. The NWS Bountiful forecast showed Tuesday reaching 75°F under partly sunny skies with only a slight chance of afternoon showers. Wednesday's forecast called for sunshine and 74°F, with high pressure building through the weekend.

If a flash-flood warning is issued for your area, move to higher ground. Residents who encounter flooded roadways should turn around. The NWS advises that a few inches of moving water can sweep away a person or vehicle.