The 2017-18 “water year” ended yesterday with a record dry September. But now the new water year, which began today, is bringing storms that are expected to deliver heavy rain.
The National Weather Service’s Salt Lake City office has issued a flash-flood watch for most of Utah in light of heavy rain that is expected through Wednesday. Forecasters say ponding on roadways statewide is also a potential problem as the remnants of Tropical Storm Rosa reach Utah and drop about 1 inch to 1.25 inches at the airport.
“There’s going to be some flash flooding in the south,” said Mike Conger, a weather service meteorologist, noting that slot canyons and dry streambeds are most susceptible.
“Up here [in northern Utah] we have burn scars that are vulnerable” to mudslides and debris flows, he added.
Conger said forecasters expect more storms later in the week after a brief reprieve. Temperatures are also expected to drop and potentially bring snow to the mountains.
The weather service recorded just a trace of rain during the entire month of September at the Salt Lake City International Airport. That’s only happened four other times in 144 years of weather recordkeeping in Salt Lake City, and September 2018 is now tied for the least precipitation.
For the entire water year, October 2017 through September 2018, the weather service measured 10.5 inches at the airport, compared to an average of 16.1 inches over the past 30 years.
September was also unusually warm. Nighttime temperatures were 9 degrees higher than the 30-year average and daytime temperatures were 8 degrees higher than normal.