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How would you do things differently if you knew two weeks ago that a winter pollution episode was settling in? Would you try to slow the buildup by driving less? Would you avoid the high pollution by extending a holiday vacation somewhere else?

Planning like that for winter inversions might soon be practical, thanks to new forecast methods developed by the Utah Climate Center. The center has found a way to forecast winter inversions as far as a month ahead, and the predictions are remarkably accurate, said State Climatologist Rob Gillies.

"We ended up predicting this inversion," he said Wednesday, "a month prior."

Climate Center scientists published a scientific paper on the trend more than two years ago. It's part of a series that links climate patterns far away to events in Utah.

Around two weeks ago, his team input data on climate patterns in the Western Pacific and ran it through a model that predicted an inversion would start building in the Wasatch Front a few days before New Year's and last through the middle of next week.

And that's exactly what's shaping up, to the dismay of those living in and visiting northern Utah.

Fine-particle pollution started climbing around late Saturday as storms tapered off and high pressure began to build. And the National Weather Service's Salt Lake City office expects the haze to stick around another week — just as the climate center's pre-Christmas computer run suggested.

"We're looking at a stagnant pattern here at least until early next week," said Mike Conger, a weather service forecaster. "Urban haze will be a big issue because there's nothing to circulate" the foul air.

PM 2.5 episodes in Utah are part pollution, part geography and part weather. High pressure creates a kind of seal over Utah's populated valleys that traps soot from combustion, solvent fumes and other chemical pollutants. The pollution builds up as long as the pressure holds — sometimes for weeks at a time between November and mid-February.

The pattern has been known to make the Salt Lake and the Cache valleys among the most polluted areas in the nation from time to time, and the state recently submitted some plans for cutting emissions and bringing PM 2.5 back into "healthy" levels all the time.

The weather service usually has a pretty good feel for inversions no more than a week ahead. The state Division of Air Quality makes its forecasts with the next three days in mind — and sometimes conditions change so fast from good to bad or bad to good that is has to alter forecasts within a few hours of making them.

Thursday afternoon, air-quality officials kept "No Burn" restrictions in place for Salt Lake, Davis, Utah, Weber and Cache counties. And "Voluntary No Burn" actions were suggested for Tooele, Box Elder, Duchesne and Uintah counties.

Both designations point to deteriorating air-quality conditions. Brock LeBaron, deputy director of the state air-quality office, noted that all signs — and forecasts — indicate it will get worse.

"It's not going to be good for the public."

LeBaron added that the climate center inversion prediction is just one factor air-quality scientists consider when they make decisions about forecasts.

Meanwhile, he shared Utah State University air-pollution expert Randy Martin's view that it might be a valuable tool someday, after its track record has been proven.

For instance, inversion predictions could help regulators avert pollution buildups. It could aid inversion-sensitive people in deciding how to protect their own health from bad air. It also could be used to address inversions in the Uinta Basin, which has an unusual wintertime ozone problem that also deepens during high-pressure periods.

"We're trying to extend it more into regional situations and not just on the Wasatch Front," he said.

Michelle Hofmann, a pediatrician and founder of the clean-air advocacy group Breathe Utah, said many people already take measures throughout the inversion season to protect their health and their children's.

But reliably predicting inversions ahead of time would make it possible for everyone to do more to scale back emissions, she said. "People want to do better if they can."

Linda Johnson of the League of Women Voters agreed it would be a useful tool, but she's not sure Utah regulators will use it.

"The problem here is the will is missing among the entities that need to do something about it," said Johnson, a member of Salt Lake County's environmental oversight committee and a participant in the state's year-long stakeholder process to address PM 2.5 pollution.

"It's got to be a whole, united effort."

For those who might be curious, the climate center's inversion prediction model hints of another inversion early next month. But it's too soon to say for sure, Gillies noted. The outlook will be clearer when his team runs the model again in a week or so.

Twitter: @judyfutah —

How to help

O There are many resources for people looking for ways to ease their impact on northern Utah's air. Here are some links:

Care to Clear the Air >

Choose Clean Air >

Salt Lake Chamber of Commerce >