Gusts swept in tiny dirt particles from the Sevier Dry Lake and the Sevier Desert on Tuesday morning, then began lifting dust from the salt flats west of the Great Salt Lake by afternoon, according to National Weather Service satellites.
The heavy plumes - along with high readings for PM 10 early Tuesday morning - prompted state air-quality officials to issue a health advisory for people in sensitive groups. The very old, the very young and people with heart and lung trouble needed to avoid exerting themselves in the dust, the advisory said.
"This is a fairly typical dust storm that we have" in spring, said Bob Dalley, who oversees air monitoring for the state. Wind storms kick up the dust this way two or three times a year, he noted.
But Bryce Bird, planning branch manager for the state Division of Air Quality, pointed out: "We're seeing some of the highest [PM 10] levels we've seen in a long time."
Could last summer's wildfires and years of drought be partly to blame?
It's too soon to tell for sure, said Bird.
State air-quality experts will study the weather maps and wind patterns. They might need the data connecting Tuesday's storms to the northern Utah dust spikes to convince the U.S. Environmental Protection Agency that man-made pollution wasn't responsible for the high air-pollution readings.
Alan Moller, a meteorologist with the Utah Climate Center at Utah State University, said the Milford Flats fire last summer and the drought "could be a factor." Hot temperatures over the weekend and on Monday might have left the top layers of soil vulnerable to widespread winds that gusted at around 50 mph in much of the state, he said.
The winds came from the south, the direction of the fires, he added. "There's another clue the fires were contributing to the dust."
It's a connection Randy Parker of the Utah Farm Bureau is also making. He was in Washington, D.C., with the Utah Partners for Conservation on Tuesday to make a pitch to Congress for mounting a war on cheatgrass, which is making Western landscapes susceptible to wildfire.
He watched the dust blow into the Salt Lake Valley on Monday night during a son's soccer game.
"You could probably assume that some of those areas - not just in last summer's fires in Milford Flats, but from the drought in the last decade - are part of it," he said of the dust.
By Tuesday afternoon, snow was falling in valleys that had seen 70-degree temperatures the previous day, and air monitoring officials had called off the health alert in Utah, Salt Lake, Davis and Weber counties.
The cold set in and promised to stick around through the night and into today, according to the weather service. Temperatures nearing freezing were expected overnight and daytime highs were expected to be in the mid-40s - about 10 degrees below normal - under partly cloudy skies.
Snow showers were expected in the mountains.
But things will warm up and the skies will clear beginning Thursday, the weather service said.
* Dust blown across Utah by overnight winds caused sharp spikes in real-time air monitors.
* The highest reading for PM 10 was 859 micrograms per cubic meter of air recorded at 4 a.m. at Hawthorne Elementary in Salt Lake City. A measurement just north of Salt Lake City reached 820 at 3 a.m.
* A reading of 566 in Lindon was logged at 6 a.m. And an air monitor in Ogden showed a reading of 574 at 4 a.m.
* State and federal regulators don't focus on hourly readings. Instead, they study daily trends as more meaningful indicators of air quality. And it was uncertain whether the heavy dust would hang around long enough Tuesday to count as a significant air-quality problem, according to that measure.
* PM 10 is the term used to describe microscopic particles of dust and pollution. PM 10 particles are about one-tenth the diameter of a human hair, about four times the size of the particles generally measured in Utah's wintertime inversions, PM 2.5.