Monsoons in May? Not quite, but it may feel like that in Utah into next week

Motorists drive on I-215 in the rain in Holladay on March 15. A "strange" pattern developing over the West may cause weather that's "reminiscent" of a summer monsoon pattern, meteorologists say.

Motorists drive on I-215 in the rain in Holladay on March 15. A "strange" pattern developing over the West may cause weather that's "reminiscent" of a summer monsoon pattern, meteorologists say. (Jeffrey D. Allred, Deseret News)


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SALT LAKE CITY — Utah's monsoon season typically begins in early July as moisture from the Gulf of Mexico enters the American Southwest because of traditional weather patterns that develop over North America in the summer.

This phenomenon often continues into September. But Utahns will get a preview of the monsoon pattern this weekend and into early next week — sort of.

The National Weather Service's Las Vegas office tweeted Wednesday that a Rex Block is setting up over the West. This, according to the agency, is when a low-pressure system moves below a stationary high-pressure system located closer to the North Pole. "Unsettled, stormy weather" is typically experienced in the area of the low-pressure system.

The end result, in this case, is something "reminiscent" of a monsoon pattern, KSL meteorologist Matt Johnson explains. The pattern is forecast to push a low-pressure system from the Four Corners region northwest into northern Utah over the weekend before it moves west through Nevada.

"It's way early to see a pattern like this. I'm not sure what it means, but it should last about 10 days," he said, calling it as he reviewed the long-term forecasts. "I don't think this is the start of the monsoon season; however, this is a strange 10-day event of seeing kind of a monsoon pattern. It's just strange."

The National Weather Service's Climate Prediction Center lists the Pacific Northwest as having a strong probability of hotter temperatures and drier-than-normal precipitation because that's where the high-pressure system will likely park over.

But it says Utah has a stronger probability of having above-normal precipitation and warmer-than-normal temperatures beginning this weekend and heading into next week, as this pattern develops. For example, the current forecast has high temperatures soaring into the 80s across the Wasatch Front along with possible showers.

The same goes for pretty much the rest of the southern half of the West, with Arizona and New Mexico having the strongest precipitation odds. Johnson calls this a "monsoon-like setup," where moisture from the Gulf of Mexico enters the Southwest and ventures northward.

This pattern could produce some pop-up showers in Utah Friday but likely won't bring any widespread showers until Saturday and Sunday. This pattern continues into next week, as models show moisture moving in from the southeast. The long-range forecast calls for the higher precipitation odds to linger through May 21.

Full seven-day forecasts for areas across Utah can be found online, at the KSL Weather Center.

This pattern could potentially ease Utah's remaining drought conditions, especially in areas that haven't received as many storms this spring. However, since it could produce pockets of heavy rain or even dry thunderstorms, it may produce new flooding or fire risks.

"Not all of these storms are going to be soaking storms," he said. "And we've also got to look out for the chance for a heavy monsoon-type thunderstorm on top of snowpack in southern or central — even northern — Utah, and you've got a really big problem because we can get flooding even without the snowpack in a monsoon-like thunderstorm. It's definitely raising eyebrows, (and) we've got to watch for it."

The bizarre pattern continues the "outlier mode" that the West has been in for months, resulting in record-setting snow collection in the mountains, Johnson adds.

That said, it's still too early to know what it means for the actual monsoon season.

"Are we leaving 'outlier mode' or are we now in kind of this still hard-to-predict atmospheric behavior?" he said. "That's something that goes through my mind as I think about this setup."

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Carter Williams is a reporter who covers general news, local government, outdoors, history and sports for KSL.com.

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