EMERY COUNTY, Utah — The National Weather Service said what happened in Emery County on Monday was, in a sense, a “perfect storm” of weather elements combined to create such a severe flash flood — one that took the lives of two young girls.
Glen Merrill has been a meteorologist with the National Weather Service in Salt Lake City for 11 years.
“Many states, at the top of of their list, is tornadoes or hurricanes,” said Merrill. “In Utah, the top of our list is flash flooding.”
In the San Rafael Swell area, which includes Little Wildhorse Canyon, a thunderstorm moving 20 miles per hour combined with intense rainfall and hail turn the canyon floors into a slurry of debris-like flow.
“It was a bad deal,” said Merrill. “Any time you get a thunderstorm with heavy rain in canyon country, it’s not a good thing.”
Rainfall amounted to about a half an inch of rain, in an intense burst that lasted about 30-40 minutes.
Steve Szoke, the director of training for the American Canyoneering Association, said it’s always better to prevent going to places when there is a flash flood risk — but sometimes, you just get caught.
A 10 percent chance of rain may look like a small percentage, but Szoke said it means somewhere there will be 10 percent rain.
And if you get caught in it, Szoke said you can never outrun a flash flood.
“It is a turn and run up the side of the hill or find a high ground as quickly as possible,” said Szoke.
Unfortunately, what happened on Monday was possible.
In their two-day flash flood rating, the National Weather Service listed the San Rafael Swell area as “possible” flash flood — meaning the slot canyons, dry washes and small streams may experience flash flooding.
“Unfortunately, there are inherent risks in remote terrain, and several things came together to aid this tragic incident,” said Merrill.
Merrill said NWS will be evaluating what happened on site in the coming days to see what they can do to improve messaging throughout the state — specially for flash flood warnings.