Remnants of Hurricane Rachel merging with a cold Pacific Northwest storm system are forecast to bring heavy rain and a 20-degree temperature drop to Alpine, Highland, Cedar Hills, and Lehi starting Saturday, Oct. 10.
The National Weather Service Salt Lake City stated on Wednesday, Oct. 7, that tropical moisture interacting with the strong system will bring widespread rain to Utah from late Saturday through at least Tuesday.
Meteorologist Hayden Mahan of the NWS in Salt Lake City told KSL on Thursday, Oct. 8, that the agency is meeting with partner agencies to decide whether to issue a flood watch. Mahan identified Sunday, Oct. 11, and Monday, Oct. 12, as the days with the strongest potential for flooding.
The flash flood risk extends beyond slot canyons, dry washes, and burn scars to include urban areas with poor drainage and main-stem rivers. Mahan told KSL that officials must monitor these areas for potentially significant water and flash flooding issues.
The storm's exact path remains uncertain. ABC4 Utah reported on Thursday, Oct. 8, that the National Hurricane Center forecast shows Rachel moving as a tropical storm through the Southern California coastline before becoming a tropical depression in southwest Utah by Sunday night. Mahan told St. George Utah News that some models project the track further west while others suggest an eastward movement.
KSL Weather models project many mountain areas could receive 3 inches or more of precipitation by Wednesday night, Oct. 14. Communities in northern Utah, including the Salt Lake City area, could see between 1.5 and 2 inches or more over that same period.
Temperatures in the Alpine-Lehi corridor were running 10 to 15 degrees above average on Thursday, Oct. 8, with highs in the low to mid-80s, according to ABC4. Highs are expected to fall to the 60s in northern Utah by early next week as the storm moves through.
This weather arrives while more than 75% of Utah remains in severe or extreme drought. The NWS confirmed that extreme drought conditions persist across much of the state in a monthly Drought Impact Statement released Tuesday, Oct. 6. Mahan noted the moisture could improve soil moisture levels and spring snowpack runoff, though flooding remains the immediate concern.
The unsettled weather is expected to last through approximately Wednesday, Oct. 14, driven by the moisture from Rachel and a slow-moving cutoff low-pressure system, according to Mahan.
As of Thursday, Oct. 8, no formal flood watch had been issued for Utah County. In an advisory posted Tuesday, Oct. 6, the NWS urged residents with outdoor plans to monitor forecasts and make backup plans at weather.gov/slc.
