Alpine, Highland, Cedar Hills and Lehi residents face heavy rain and isolated thunderstorms through Friday, Oct. 23, as a cut-off low-pressure system pushes across Utah.
The National Weather Service (NWS) has issued Flood Watches for portions of central and southern Utah, some extending through midnight Oct. 23, according to ABC4 Utah meteorologist Alana Brophy. Areas under the watch could receive 2 to 3 inches of rainfall. A marginal flash-flood risk extends into northern Utah on Thursday, Oct. 22, as the storm's second wave pushes through the state.
The system is pulling tropical moisture from the remnants of Hurricane Trudy off Mexico's coast, according to the Daily Mail. That moisture, combined with wind shear, is fueling heavy downpours and severe thunderstorms across the Southwest.
Rain is already falling locally. Lehi reported heavy drizzle and 60-degree temperatures as of Wednesday, Oct. 21, afternoon, according to the Utah Ledger. The forecast calls for rain Thursday with a high near 71 degrees, then cloudy skies Friday with highs around 60.
The Storm Prediction Center (SPC) placed far southern Utah under a marginal to slight risk for severe weather on Wednesday, levels 1 and 2 out of 5, Brophy reported. The greatest threat there is large hail, but damaging wind gusts up to 70 mph and isolated tornadoes are also possible. For Thursday, the SPC placed most of western and southern Utah under a separate marginal risk, level 1 out of 5, for large hail and damaging wind gusts.
The NWS Salt Lake City office warned of "a high risk of flash flooding across many southern Utah parks and recreation areas Wednesday and Thursday," the Las Vegas Review-Journal reported. The office advised travelers to avoid dry washes, slot canyons, backcountry roads and low-water crossings.
Soils across southern Utah are already saturated from a previous round of tropical moisture, ABC4 reported. That means excess runoff through canyons, burn scars and low-lying areas is likely.
For the four north Utah County cities, the main concern is periods of rain and isolated thunderstorms Wednesday evening through Thursday. Scattered showers are expected to increase across central Utah on Wednesday evening and push northward. Winds will become gusty out of the south as the low-pressure system tracks through.
By Friday, an upper-level low will dig south across northern Utah, keeping rain chances alive and dropping snow levels. Forecasts differ on the exact elevation, with Brophy's reports placing snow levels between 8,000 and 8,500 feet. Several inches of snow are possible in the Upper Cottonwoods and Uintas, though valley areas will see rain only.
The storm is expected to exit by Saturday, Oct. 24, afternoon, clearing the way for a dry weekend with highs in the 50s across northern Utah.
Utah's emergency management agency advises residents to keep cell phones and radios charged, have at least three days of food, water and medicine on hand, and avoid driving through flooded roadways. The state's flood safety page warns that just 12 inches of moving water can float a car.
