Tropical moisture from Hurricane Polo will push into northern Utah starting Sunday night, Sept. 27, bringing a flash flood risk to the Bountiful and Farmington area through Tuesday.

The Weather Prediction Center (WPC) placed areas along and south of Interstate 80 under a 15% "slight" risk of flash flooding, ABC4 meteorologist Noah Price reported Sunday, Sept. 27. That zone includes the Bountiful and Farmington area.

"This is an impressive surge of moisture we'll be seeing which will produce some heavy rainfall totals and the likelihood for flash flooding," Price said.

An upper-level low pressure system digging across California and the Great Basin is steering moisture from Hurricane Polo northeast into Utah. Hurricane Odalys, also churning in the eastern Pacific, will add to the moisture stream. A cold front riding with the system will drop temperatures from Sunday's low-to-mid 80s into the 60s and 70s by Monday and Tuesday.

The National Weather Service in Salt Lake City issued a Flash Flood Watch Sunday morning, Sept. 27, for central and southern Utah, in effect from Monday morning through early Tuesday morning. The watch warns that isolated storms could produce rainfall rates above 1 inch per hour. That watch does not explicitly name Davis County, but the WPC's slight-risk zone extends into the area.

Southern Utah faces the steepest danger. The WPC issued a Day 3 Moderate risk of excessive rainfall there, meaning a 40% chance of flash flooding within 25 miles. ABC4 reported that designation had never been issued for southern Utah before, though that claim has not been independently verified against WPC records.

Fox Weather reported Sunday, Sept. 27, that Polo was weakening after a record stretch at Category 5 strength, with peak winds of 180 mph and a central pressure of 892 millibars. The storm is forecast to make landfall in Baja California Sur on Monday, Sept. 28.

Showers and thunderstorms are expected to spread from south to north Sunday night, becoming widespread Monday. Rain will continue into Tuesday before moisture dissipates Tuesday evening. Drier conditions and temperatures climbing back into the 70s and 80s are forecast by Wednesday, Sept. 30, and Thursday.

What Bountiful and Farmington residents should know

Bountiful City's floodplain safety guide warns that flash floods rank first among flood-related deaths in the United States. Areas with steep slopes, narrow stream valleys and storm drain systems are the most vulnerable.

The city advises residents not to walk through moving water. Six inches can knock a person down. Do not drive into flooded roadways. One foot of water can float many vehicles, and two feet will carry away almost any car or truck.

Residents can monitor conditions through the National Weather Service or sign up for local emergency alerts through Davis County.