A high pressure system locking cold air over Utah's urban valleys is predicted to keep overnight temperatures in single digits or below zero in some areas into the coming weekend.
What's more, not only will the morning air be bone-chilling, it will be increasingly dirty as automobile and industrial emissions are trapped by northern Utah's dreaded winter valley air inversions, the National Weather Service warned.
"The steady warming aloft Wednesday and beyond will serve to create rather strong valley inversions, especially throughout central and northern Utah. Steadily building urban haze [will be] a given this week," forecasters stated.
The Utah Division of Air Quality projected "yellow," or moderately compromised breathability Tuesday and Wednesday for Salt Lake, Davis, Utah, Weber, Cache and Uintah counties. Yellow grades bring with them "voluntary action" recommendations for choosing mass transit over car travel and limiting outdoor activities for young children, the elderly and those with compromised lung function.