Utah forecast: Here comes the snow, there goes the smog

Utah's days of "Red," or unhealthy air alerts are numbered, and that number appears to be one.

The Utah Division of Air Quality rated most of the state on Wednesday as "Red," meaning all burning was banned and the elderly, young children and those with compromise lung or heart health were urged to avoid outdoor activity. Motorists were asked to use mass transit or work from home rather than add to the inversion-worsened smog plaguing the state's urban valleys.

However, on Thursday morning that cold Pacific air begins to flow out of the Northwest and into the Wasatch Range. The National Weather Service has issued a winter storm watch for much of the state, from Logan running south through Ogden, Salt Lake City and Provo to near Escalante, west to the Nevada border, southwest to St. George, and also to sections of eastern and southeastern Utah.

The storm advisory runs through Saturday morning. Forecasters expect snowfall of 3 to 9 inches in the lower elevations with the state's mountains bracing for 1-2 feet of new snow.

The infusion of fresh, cold air, along with that snowfall, will scrub the atmosphere of the particulate and automotive pollution that has choked the state's valleys for nearly two weeks. While DAQ initially predicted "Red" air quality status for Salt Lake, Davis, Weber, Cache, Tooele, Utah and Box Elder counties again on Thursday, those conditions were expected to improve dramatically as the storm makes itself felt by mid-day.

However, that expected new snowfall translates to an increased chance for avalanches. The Utah Avalanche Center elevated the danger rating for the mountains of Salt Lake, Ogden, Provo, Moab, Logan and the Uintas Range to "moderate" for Thursday.

High temperatures Wednesday in northern Utah were expected to reach the upper-30s. Overnight lows early Thursday were to dip only a few degrees, into the low- to mid-30s. Thursday's highs were forecast to be in the low-40s before the storm system moved in behind winds of 10-20 mph.

Southern Utahns looked for highs in the upper-50s Wednesday, followed by overnight lows around 40 and Thursday highs around 40 degrees as the storm system settles in, again propelled 10-20 mph winds.

Salt Lake City's high Wednesday was pegged at 38, with an overnight low of 34 to follow and a high of 42 degrees on Thursday; Ogden looked for 37, 33 and 39 degrees; Provo 36, 29 and 43; Logan 31, 25 and 35; Wendover 27, 22 and 29; Duchesne 23, 4 and 28; Cedar City 45, 32 and 42; St. George 57, 39 and 54; and Moab 25, 11 and 36 degrees.

remims@sltrib.com