A strong high-pressure system that has wrapped a stranglehold of bad air around the Wasatch Front this week - and didn't clear out on Friday as expected - should finally give way when a storm system of growing intensity sweeps through the northern part of the state this weekend.

National Weather Service forecaster Randy Graham said Friday that a weak system arriving today was expected to break up the inversion, to be followed by a stronger system on Sunday that could bring 6 to 12 inches of new snow in the mountains and rain and possible snow to valley locations.

"It looks pretty moist, though not real powerful," Graham said. "It won't be a huge event, but it will be a nice layer of new snow for the mountains, and it will clear things out."

The high pressure system that has been building since last weekend spiked Friday afternoon to levels considered "unhealthful."

As evening commuters prepared to leave work, the wind forecasters saw on the horizon did not materialize and pollution remained trapped in northern Utah valleys below a mass of warm air.

Bob Dalley, director of air monitoring for the state, noted that a sample taken at Hawthorne Elementary in Salt Lake City between 1 p.m. and 2 p.m. Friday reached 72 micrograms of PM 2.5 for every cubic meter of air. The U.S. Environmental Protection Agency considers concentrations above 65.5 unhealthy. PM 2.5 is fine-particle pollution, microscopic soot, that is linked to respiratory distress and heart trouble.

High temperatures should reach the low 40s today, dropping to the high 30s on Sunday when the main portion of the storm system moves through.