Unhealthy air will continue to plague much of Utah until Friday, when a “significant” snowstorm is expected to clear out lingering Wasatch Front and Cache Valley inversions.
An inversion forms when warmer air at higher altitudes traps colder air — and pollution — below it, according to the Utah Department of Environmental Quality. That “lid” of warmer air then concentrates pollution, making for hazy skies. Utah inversions typically happen from about November through February each year.
Salt Lake County’s air quality is forecast to remain “unhealthy for sensitive groups” through Thursday, then transition to “moderate” on Friday as the storm arrives. Nearly all other Utah counties are expected to see “moderate” air quality through Friday, save for Carbon, Grand and Washington counties, where air quality is currently “good.”
The Friday storm should hit northern and central Utah and continue through the weekend, with “heavy mountain snow” accumulations expected, according to the National Weather Service.
(Francisco Kjolseth | The Salt Lake Tribune) Air quality deteriorates in the Salt Lake valley on Tuesday, Nov. 28, 2023, as inversion conditions are expected to increase trapped pollution this week.
Snow is also expected in the Cache Valley, the Wasatch Back and along Salt Lake Valley benches from early Friday through early Monday.
In the Salt Lake City area, there is:
• a 20% chance of snow after 11 p.m. on Thursday.
• a 70% chance of snow on Friday, with accumulations of 3-5 inches possible.
• a 60% chance of snow on Friday night, with accumulations of 2-4 inches possible.
• an 80% chance of snow on Saturday, with accumulations of 3-5 inches possible.
Snow is expected to continue late Saturday into Sunday, and could be heavy at times. That’s because the weather service describes this storm system as “upside-down” — instead of waning snow levels, “we are likely to see rising snow levels through the duration of the storm.”
And it’s going to be cold. The Salt Lake City forecast calls for a high of 32 and a low of 24 on Thursday; a high of 29 and a low of 22 on Friday; a high of 30 and a low of 26 on Saturday; and a high of 32 and a low of 25 on Sunday.
That’s considerably colder than normal for this time of year, when average daytime highs are usually in the low to mid-40s and average overnight lows are in the mid-30s.
Snowfall is expected to taper off early Monday, with lingering mountain snow showers. And it should begin to warm up. According to the weather service, that’s when a “strong warming trend” is expected — bringing temperatures up to the low to mid-40s.
In southern Utah, 3-6 inches of mountain snow is expected over the next few days, and some valley snow accumulation is forecast. St. George area may only see rain, though, but rain could mix with snowfall there Friday.
Daytime highs there will hover around 50 through Sunday, then rise to the mid-50s on Monday and about 60 on Tuesday. Overnight lows will be in the low to mid-30s. Normal highs in St. George at this time of year are 55-57; normal lows are in the low 30s.