Despite record warm November, inversion pollution builds in Northern Utah

Friday , December 01, 2017 - 5:10 PM

LEIA LARSEN, Standard-Examiner Staff

The National Weather Service confirmed Salt Lake City and other areas in Northern Utah saw their warmest November on record. 

A lot of those unusually warm temperatures came “toward the end of the month, around Thanksgiving, as most people living around here probably realize,” said Nick Carr, a weather service meteorologist.

Cities in the region saw high temperatures of about 68 or 69 degrees, due in part to warm southerly winds. 

“The rest of the month we had a lot of days a little bit above normal,” Carr said.

November 2017’s average daily temperature was 47.8 degrees, compared to the month’s 30-year average of 40.0 degrees. The previous November record was set last year, which saw an average daily temperature of 47.0 degrees.

The month was also unusually devoid of storms, which helped things stay toasty.

“The storm track held north — Idaho and Montana got most of the storms,” Carr said. “Usually in November we have systems that come through bring a cold front.”

Despite the warm weather, an inversion spell settled in Northern Utah on Tuesday, Nov. 28, trapping smog in the valley. While inversions form when temperatures in the valley are colder than the mountains, they can still happen during balmy weather.

“It’s an issue we get because of the short amount of daylight,” Carr said. “It doesn’t have to be super cold or have snow on the ground this time of year to have inversion.”

That’s because sunlight mixes air in the upper and lower atmosphere and helps blow things out of the valley. Without storms to move the air below, particulate pollutions have slowly built over the week in Weber County.

As of Friday afternoon, the Utah Division of Air Quality reported particulate matter levels in the moderate range. 

Bo Call, manager of the air monitoring section for the division, said air quality conditions would likely be worse if it were colder and snow had accumulated on the valley floor. 

“With the atmospheric chemistry that goes on in our valley, it forms ammonium nitrate when it’s cold,” he said. “We don’t necessarily pollute any less — you still have the same tailpipe emissions — but during an inversion it combines in the atmosphere to form particulate pollution.”

Snow both insulates to keep things cold and reflects sunlight to create more photochemical reactions.  

Call expects particulate pollution to continue to build in Northern Utah until the next storm front.

“Cars are still the single biggest source of pollution we have,” he said. “Everyone can do their part by driving less and keeping their vehicles maintained.”

The National Weather Service is calling for snow and rain in Ogden on Sunday with temperatures dropping to the 30s on Monday. 

Looking ahead, Carr said the odds are stacked that December will be warmer than usual, too. Nationwide, weather patterns favor a warmer Western U.S. and a cooler Eastern U.S.

“After this next system comes through, we will be in a pattern that keeps us warmish,” he said. “We probably won’t get back up into the 60s without help from stronger winds, but we look warmer than average.”

Contact Reporter Leia Larsen at 801-625-4289 or Follow her on or on Twitter @LeiaLarsen

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