Story updated Tuesday at 3:20 p.m.
PHOENIX — A powerful storm system brought flooding and power outages to parts of metro Phoenix on Monday evening, and more severe weather could be on the way this week.
Flash flooding remains a concern; the National Weather Service has issued a flash flood watch for much of Arizona, including Maricopa County, starting Wednesday morning.
Coming on the heels of early morning storms that pounded the East Valley, severe thunderstorms moved over Phoenix during the evening rush hour Monday. The National Weather Service reported penny- to nickel-size hail north of downtown Phoenix and in Paradise Valley.
A severe thunderstorm over Cave Creek on Monday afternoon prompted the weather service to issue a tornado warning for the area. It was the Phoenix office’s first tornado warning in five years.
Videos of the possible twister surfaced on social media, and the National Weather Service confirmed Tuesday that a tornado did touch down in New River.
People posted photos showing walls of dust south of Phoenix. Visibility was reduced to less than a quarter of a mile along Interstate 10 from Casa Grande to Tucson.
Storms dropped more than 2 inches of rain in parts of Mesa and 3 inches in Apache Junction. Record amounts of rain fell in Scottsdale, north Phoenix and Surprise.
— Ian Schwartz (@SchwartzTV) September 23, 2019
Mesa Fire & Medical rescued several stranded drivers in their vehicles, and the National Weather Service reported street flooding in parts of Mesa, Apache Junction and Fountain Hills.
The atmospheric setup
Ahead of Monday’s storm system, ample moisture from the remnants of tropical storms Lorena and Mario, which dissipated last weekend, fueled the atmosphere.
The atmospheric setup Monday was similar to two previous severe weather events over Arizona. In late September 2014, an intense line of thunderstorms moved through the Valley and central Arizona bringing high wind gusts near 70 mph that damaged some of the terminals at Phoenix Sky Harbor International Airport.
In early October 2010, Phoenix saw its largest hailstone ever, at 3 inches in diameter – nearly the size of a baseball. This was a rare event for Phoenix, as hail this big primarily occurs over the Great Plains. This was also the same storm system where multiple tornadoes touched down in the high country, including one that damaged homes in Bellemont.
What you need to know
Big hail and tornadoes are extremely rare in Arizona, but they aren’t out of the question for today. Have an action plan in case severe weather strikes.
If a thunderstorm is approaching, make sure you have a safe and sturdy structure to shelter in. The National Weather Service also recommends staying away from windows and avoiding corded electrical equipment. If you’re in a vehicle, safely drive to a sturdy structure for shelter.
Keep in contact with loved ones by creating a communication plan. Prepare your home by securing loose objects outside and closing doors and windows.
Have extra batteries and chargers for your cellphone ready, in case the power goes out. More safety tips about how to prepare for severe weather can be found here.
Most importantly, do not drive into flooded roadways. It only takes 12 inches of water to float compact vehicles.