Monsoon season arrives a month early this summer
Torrents of very localized rain fell in the Wasatch Back Wednesday afternoon and through Wednesday night.
On Wednesday, areas in and around Park City got about three-quarters of an inch of rain in a very short amount of time. The Heber City area received about a quarter inch as powerful storm cells moved through the Wasatch range.
Glen Merrill, a hydrologist with the National Oceanic and Atmospheric administration, said what's happening is typical of monsoonal thunderstorms. He said they don't usually last too long, but there can be extremely heavy local rain leading to runoff and flash flooding of local streams.
Capt. Andrew Wright from the Summit County Sheriff’s Office said no one reported damages from the violent storms that shook homes and scared pets during the early hours of Thursday morning.
Merrill said the storm cells typically originate over the mountains and track into valley areas as they quickly move through.
"And when we're dealing with monsoonal showers and thunderstorms, they're highly localized, and they're individual storm cells, individual thunderstorms that form primarily from the heating of the day," Merrill said. "When we heat the ground during the day, that hot air rises. When that hot air rises, it lifts into the atmosphere and forms these thunderstorm cells."
Meteorologists predicted an early monsoon season, and Merrill said it is related to broader climate conditions from this past winter.
"It was the lack of snow across southern latitudes of the Desert Southwest in the mountain areas and the storm track well to our north that allowed this high-pressure system to form earlier than it typically does across the Four Corners region," Merrill said.
Merrill said the summer rainfall is localized and will not replenish area reservoirs or eradicate drought conditions.
"We receive about 95% of our water supply from snowmelt runoff into our streams that's then captured in our reservoirs." "So," Merrill said, "to really make a dent in this drought, we're already looking forward to next winter and the year after that we need above-average precipitation well above-average precipitation during the winter season, to build that snowpack, to store water as a bank in that snowpack until the spring snowmelt runoff."
Merrill said the moisture could help prevent wildfires by keeping the natural fuels moist, but the threat of lightening remains a concern.
Meteorologists are expecting the holiday weekend to usher out the monsoon with more normal, drier high pressure settling into the Wasatch Back over the coming week.