A region typically accustomed to scorching temperatures rather than persistent rain is now bracing for severe downpours, significantly elevating the risk of flash floods that can emerge and turn deadly within minutes.
Tropical Storm Priscilla, having been downgraded from a powerful hurricane, has diminished in strength over the eastern Pacific near Mexico’s Baja California peninsula. However, the storm’s remnants still carry substantial moisture and are now advancing towards the southwestern United States, where flood warnings were issued on Thursday.
Meteorologists anticipate that rain bands from Priscilla will drench parts of Arizona, Utah, New Mexico, and Colorado throughout the weekend. These areas could experience as much precipitation in a few hours as they typically receive over an entire year. The grave potential for such intense rainfall is highlighted by recent deadly flooding events in Texas and New Mexico.
“We don’t want to see people caught up in the hazards we are going to be seeing,” said meteorologist Robert Rickey with the National Weather Service in Flagstaff, Arizona.
Northern Arizona is most at risk, with 2 to 3 inches (5 to 8 centimeters) of rain likely in and around Flagstaff, the national park gateway city south of the Grand Canyon.
Some areas could get even more, said Rickey, but where exactly that will happen is impossible to predict very long in advance.
High-elevation Flagstaff gets ample rain, upward of 2 feet (60 centimeters) a year, though not often in such big doses. Southwestern and northeastern Arizona see far less, in some places as little as 5 inches (13 centimeters) or less a year; Phoenix gets just 7 or 8 inches (18 to 20 centimeters) a year.
In such deserts, downpours on paved, urban landscapes with minimal drainage infrastructure and in backcountry areas mazed with canyons can become deadly fast.
Worried folks headed outdoors have been calling the National Weather Service asking if they should cancel. The agency has been kept open during the government shutdown.
“I had to have that kind of frank conversation with them,” Rickey said. “Is the risk worth the reward?”
After heat, flooding is the deadliest weather phenomenon in the U.S., killing 145 people in 2024. Many victims were in their cars, braving high water that can be deceptively dangerous.
In Arizona, a “stupid motorist law” allows drivers to be billed up to $2,000 if they drive around a barricade or warning sign into a flooded area and have to be rescued.
By encouraging smarter driving, the law attempts to reduce the state’s dozens of such rescues every year. Some, though, worry the law discourages people from seeking help right away, putting them in worse danger. The law isn’t consistently enforced.
The Southwest’s desert canyons and arroyos are notorious for flash flooding risk. Even a storm miles (kilometers) upstream can turn a dry wash into a raging torrent, churning debris downstream and blocking the way out for hikers and cars.
