Monsoon rains could break exceptional drought in southwest

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Nearly 10 million people are under flash flood watch in Arizona, Colorado, New Mexico and Utah.

As heavy rains and thunderstorms will affect much of the southwest this weekend, the highest precipitation totals are expected in the state of Arizona, where some locations could reach over 6 inches. This amount of rain over such a short period of time has raised significant concerns about flash floods.

Tucson, Arizona, was under flood warning for much of the day Friday, where 1 to 4 inches of rain fell over the area, most of it accumulating overnight and early in the morning. The city has seen nearly 3 inches of rain so far this month, more than an inch above the city’s normal precipitation for the month.

Heavy rains from Thursday evening to Friday morning submerged highway ramps north of Phoenix, and more rain is expected over the weekend.
Just outside Tucson, the Vail School District alerted families on its Facebook page that due to flooding, road closures could impact bus routes on Friday. “If you live in an area prone to road closures due to flooding, you can assume that bus lines will be delayed or unavailable this morning.”

“What we would expect to see here is a widespread rain event across much of the state of Arizona,” said National Weather Service Tucson meteorologist Rob Howlett. “Looking just southeast of Arizona, many valleys will see rainfall likely between 1 and 2 inches, perhaps more in other places.”

The mountains and foothills of the southwest could see as much rain as possible with five or more inches, but even metropolitan areas, including Flagstaff and Tucson, could see 3 or more inches of precipitation throughout the weekend.

When heavy rains fall for a brief period during the strongest thunderstorms, flash floods can occur extremely quickly.

“Normally dry stream beds can instantly turn into swift torrents of water, especially under scars from burns,” CNN meteorologist Chad Myers said.

The Tucson Weather Services Office compares this weekend’s weather pattern to that of 2006 rain event which caused widespread flooding and damage in areas of Tucson. The similarities include large scars from burns in the area and soils already saturated from previous flooding earlier this month.
“Numerous burn scars scattered throughout the region will be a cause of significant concern for the widespread flash floods,” according to the Weather Prediction Center. “As such, the Weather Prediction Center has issued a moderate risk of excessive rain for parts of Arizona and New Mexico which will be applied until Sunday morning.”
Numerous fires ravaged the state in 2021, with two of the largest fires in Arizona history burning thousands of acres outside of Phoenix. The record wildfire season in 2020 left its mark with a scar of 119,978 acres in the foothills of Tucson.

“The Bighorn fire near Tucson, we will be watching this very closely for any heavy rain there as we have concerns downstream. There is potential for flash floods along these waters and rivers,” he said. Howlett said.

Heavy rains easily drain off scars from burns as the soil, when burned, becomes hydrophobic – unable to absorb water – and the vegetation that usually holds the soil in place is destroyed.

Rain to breach the drought

In the short term, these torrential rains will lead to dangerous flash floods. But in the long run, these types of rainy events bring very beneficial rains that could break up the ongoing drought in the region.

The massive heat dome brings yet another heat wave, this time covering most of the United States

Almost the entire state of Arizona – 99% – is under some level of drought, with over 80% of the state in extreme or exceptional drought.

The extent of the drought has improved in the southwest over the past week due to monsoon rains that hit the region last week. The highest level of drought has fallen from 58% to 36% and marked improvements are expected again next week, with this current wave of monsoon moisture.

The heaviest rainfall is concentrated in the drier parts of Arizona along the New Mexico border on the east side to the Utah border.

“Usually to make a really good breach in drought conditions you want to have this more regular rain that can seep deeper into the soils, but at this time of year it’s just not the right one. kind of scenarios that we see, ”Howlett said. “We have thunderstorms and a lot of them are runoff, but every drop counts.”

The sporadic and intense nature of monsoon thunderstorms frequently leads to runoff instead of moisture which effectively penetrates the soils and revives drought-stricken land. Nevertheless, any precipitation is welcome during the hottest part of the year.

“It’s going to make a difference, and we’re really counting the rain this time of year to help us with our drought conditions because for the whole year half of our rainfall occurs during the monsoon season.”

CNN’s Allison Chinchar contributed to this report.



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