Heavy rains from seasonal monsoon moisture combined with remnants of Tropical Storm Norbert on Monday dumped record amounts of rain throughout the Southwest on Monday.
These heavy downpours of rain produced dangerous flash floods that washed away freeways and residential areas in Southern California, Las Vegas, Phoenix and Tucson metropolitan areas on Monday.
Interstate 15 in Nevada had to be closed for a nearly 50-mile stretch between Las Vegas and Salt Lake City.
Nevada transportation officials said the corridor could be closed for three to four days while they try to repair it.
A detour added about 50 miles to the trip between the two major cities.
“I don’t think it can be overstated just how important I-15 is,” Utah Department of Transportation spokesman John Gleason said. “I would say the detours, in the best-case scenario, are not as convenient as I-15.”
Arizona took the biggest hit. Monday’s rainfall broke history in Phoenix, where weather records date back to 1895. Phoenix Sky Harbor Airport recorded 3.29 inches of rain, breaking the record total of 2.91 inches set more than 80 years ago, the National Weather Service reported. Monday’s rain total was more than Phoenix, Arizona usually gets in the entire three months of July, August and September.
“The richest plume of moisture from former Hurricane Norbert is pointing straight north through the Lower Colorado River Valley and into southern Nevada. Rainfall has been wildly variable but over 1 inch of rain fell in a short time in the southwest part of the Las Vegas Valley Monday,” said weather.com meteorologist Nick Wiltgen. “More troubling were the storms northeast of the city; one gauge reported 2 inches of rain in 30 minutes north of Moapa. This is an extreme amount of rain for a desert environment. NOAA estimates this type of rainfall should happen once every 500 to 1,000 years in that area, assuming no climate change.”
It not over either. More showers and thunderstorms are expected for parts of California, Arizona, Utah, Nevada and Colorado on Tuesday, reported meteorologist Dan Petersen of the Weather Prediction Center in an online forecast.
He said flash flood watches remain in effect in many of these areas, though all watches had expired in Nevada. “As drier air aloft filters into the region, coverage and amounts of rain will decline on Wednesday,” Petersen noted.