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Tucson still in middle of warm, dry winter despite 25 inches of new snow in Catalinas

Despite the 25 inches of snow that fell on Summerhaven at the beginning of the week — and another six inches due to fall on the Catalinas by the end of the week, Tucson is still in the middle of a winter that is drier and warmer than normal.

“For winter as a whole, that’s below normal,” said Rob Howlett, a meteorologist for the National Weather Service in Tucson. “This is a La Niña winter, so the weather will be drier and warmer than normal, and we can expect that to continue the rest of the winter.”

To start the week, snow not only hit the top of the Santa Catalina Mountains and other ranges in Southern Arizona, but flakes fluttered all throughout the valleys, including the metro area. A hard freeze warning was in effect, as temperatures dropped below 32 degrees across the region.

Howlett said that Tucson is in the middle of weather pattern that's been active since about November or early December. This weekend, the weather should be cool, but will warm back up by the beginning of next week.

By contrast, Howlett said, if you go back to November, the weather was dominated by high pressure activity further to the north, but since then, we've had more cold air affecting Southern Arizona.

November was a warm month, starting out with high temperatures in the low 90s for the first six days and ended as the fourth warmest November on record, NWS data shows.

December started out warm as well, with highs in the 60s before warming up into the 70s and lower 80s in the first week. By December 10, a weather system that brought much cooler temperatures broke the trend.

The weather system, which is a simple way to refer to the movement of warm and cold air over an area, that came on December 10 brought widespread rain over the valley and mountain snow showers. The winter that Tucson has been enjoying since has been characterized by the pattern of weather systems like that coming and going.

These winter weather systems that are bringing cold air and snow are also cooling off the year. Last year, 2020, was the driest and second warmest year on record, according to a December NWS Tucson report.

Some winters, Tucson has more active weather patterns. John Gluck, a meteorologist with the NWS Tucson since 1995, recalled the very active winter of 1997 and 1998.

“That winter, I can still remember it, we had seven storms in December, one in January and eight in February.,” he said about the storms like the ones that have brought rain and snow this winter.

La Niña — and its wet and cold counterpart, El Niño — affect the number and depths of the storms, qualities like the temperature and wetness of the weather systems, Gluck said. La Niña is making these weather systems warmer and drier than weather systems that Tucson gets in a normal winter.

The La Niña pattern happens about every three to seven years, as the surface waters of the the eastern and central Pacific Ocean cool down by 1-5 degrees. The countervailing pattern, El Niño, happens when ocean waters warm up.

"It alters the atmospheric weather patterns," Gluck said. "It has to do with the air's circulation. Think of it as wavy patterns; we get waves of warm air."

Howlett likened the connection between snow on the Catalinas and the ocean off Ecuador to a balancing act.

"It's something natural that occurs with the winter time," he said. "When temperatures closer to the equator warm up, Mother Nature balances out the difference, and the cooler air that was there retreats farther north. That's the waves of cool air that move through here," with the warmer air moving in behind it.

Measured at the airport, one of the driest parts of the Tucson area, Gluck said, Tucson is still 2.23 inches below normal liquid precipitation levels since October 1, and Tucson likely won’t pass that level this winter even with more rain and snow coming this weekend and throughout February.

“This is what we were expecting,” Gluck said. “We’re not surprised.” Gluck admitted that the snow was delightful all the same.

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“Maybe they’ll start up the ski lifts,” Howlett said.

Bennito L. Kelty is TucsonSentinel.com’s IDEA reporter, focusing on Inclusion, Diversity, Equity and Access stories, and a Report for America corps member.

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Paul Ingram/TucsonSentinel.com

The Santa Catalina Mountains were covered with snow after a winter storm swung through Tucson Monday night.