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If it weren't for this inversion, it would have been sprinkles and nobody would have cared. But because of this colder pocket of air, it became an icy mess. —KSL meteorologist Grant Weyman

SALT LAKE CITY — Freezing rain wreaked havoc on commuters Thursday, caused nearly 250 accidents, shut down the Salt Lake City International Airport for hours and generally baffled many who had never seen the stuff before.

Experts say freezing rain in Utah is rare.

And while Thursday may have marked the end of the icy precipitation, the 0.08 inches that had fallen by midday was the largest accumulation of freezing rain in almost 30 years, according to Trevor Alcott of the University of Utah. Alcott looks at conditions at the airport and reported that this was only the ninth incidence of freezing rain since 1940.

It was also the coldest measured, as the previous eight incidences occurred when temperatures were 26 degrees or warmer. Thursday's rain came in 20-degree weather.

KSL meteorologist Grant Weyman said the freezing rain is "very rare" for the Beehive state and can be explained best by one thing: the inversion.

"A lot of people, they see the fog and call that the inversion, but that's actually not accurate," Weyman said. "It's warm air above cold air. What warm air above cold air will do is trap whatever is in there. So if there's haze, if there's smog, it just gets trapped."

He said Utahns have seen this inversion for the past 10 days, and when it started to rain in the upper, warmer air, it came through and hit the cold valley air, creating freezing rain.

"It starts as rain and then it comes into the cold air and freezes," Weyman said. "So what it was doing in some cases it was rain on people's windshield, but it would freeze on contact with the surface. It was actually glazing ice on the bridges, the overpasses and stuff like that."

This is so unusual, he said, because storms that blow in usually come with enough wind to mix the cold and warm air and eliminate the inversion.

"If it weren't for this inversion, it would have been sprinkles and nobody would have cared," Weyman said. "But because of this colder pocket of air, it became an icy mess.

"You'd think since we often have inversion, it would happen more. … It was just the perfect storm of these really cold temperatures and this weak storm."

The unusual conditions led to a number of frustrations Thursday, especially for those on Utah's roads and those dependent on its largest airport.

Three Utah Highway Patrol troopers were also hit within three hours Thursday while responding to accidents on I-15 and all sustained minor injuries.

All airport runways were closed due to the weather conditions around 9:30 a.m. About that same time, a Frontier Airlines airplane slid while on the taxiway after losing traction while landing.

"We were about to close the runways, and that was an indication we needed to," said airport spokeswoman Barbara Gann, adding that airport officials had already noticed a decline in friction, which is how they monitor an aircraft's braking ability.

Passengers on the flight said they hardly noticed the slide and the airplane made it to its arrival gate. Gann said there was no damage to the airplane or injuries to passengers.

One of the airport's three runways reopened just before 1 p.m. and a second opened around 3:15 p.m. The runways handled both departures and arrivals.

Still, the situation caused a host of problems and Gann advised those with flights to check with their respective airlines for flight status information. With two conventions in Salt Lake City, she said hotel rooms were also scarce and suggested that those with rooms should stay in them and make sure their flights are leaving before venturing to the crowded airport.

There were multiple crashes on Utah's roadways spanning as far south as Spanish Fork.

"It's terrible," said Utah Highway Patrol Cpl. Todd Johnson. "We've got the freezing rain and Salt Lake County has more crashes than troopers can keep up with."

Even troopers who were off-duty were called in to help with crashes Thursday morning and three troopers were hit while assisting motorists.

The first freeway accident that injured a trooper occurred just after 6 a.m. Thursday on southbound I-15 near 1000 South. The trooper was out of his vehicle at the time handling the crash when he and his vehicle were struck by a car that was "driving too fast for the icy conditions," said Johnson. The trooper's injuries did not appear to be life-threatening, though he did receive stitches for a cut on his hand.

The second crash occurred around 8:30 a.m. on northbound I-15 near 5300 South when a vehicle, also traveling too fast for conditions, hit the rear end of a trooper's vehicle while the trooper was inside. That trooper was transported to the hospital as as precaution, Johnson said.

The third crash involving a trooper was near Springville in Utah County at 9:10 a.m. where the officer was assisting a vehicle that had slid off of the road near the I-15 southbound off-ramp. The trooper was in an emergency lane with his lights activated when a vehicle exited too quickly and slid into the rear of his car, pushing it into a pickup truck that had also come to help. The trooper was inside the car and he received minor injuries to his back and neck, but was not transported to a hospital.

There were a total of 128 crashes causing damage that were reported in Salt Lake County and 25 causing injuries throughout the morning, with 21 more crashes in the evening commute. Utah County saw 25 total crashes with damage and two involving injuries. Davis County recorded an additional 70 crashes.

Friday should bring warmer temperatures and an end to the rain.

Jordan School District delayed buses transporting elementary school age children by as much as an hour Thursday morning, spokesman Steve Dunham said. High school and middle school students had already been dropped off when the decision was made by school officials working, with input from local municipalities, to delay transportation for younger children around 8:30 a.m.

Dunham said parents were notified via Facebook, Twitter and the district's sky alert system so they could retrieve any waiting children from bus stops. By 9:15 a.m., the district reported that buses were back out and all tardy students Thursday morning would be excused.

The Utah Department of Transportation even urged those who work in Salt Lake City to delay their morning commutes by at least an hour due to the road conditions. UDOT spokeswoman Lisa Miller said plow crews were "out in full force."

"Make sure that if you see a plow, you slow down around them and give them room to work so they can clear the road," Miller said, noting that plows would be using a liquid chemical spray treatment for roads that are more effective on ice.

For those involved in some sort of crash on the freeways, UHP asked drivers to take the next exit if possible.

"If there are no injuries in that crash, please move off to the next exit, dial 911 and a trooper will meet you there at that exit," spokesman Dwayne Baird said. "We just want to avoid secondary crashes or having people get injured as they get out of vehicles on those icy roadways."

Salt Lake City Mayor Ralph Becker and the city's Public Services Department also urged city residents to limit driving. All 45 of the city's plows were on the roads with sanders to apply salt to main roads and steep residential streets.

Utah Transit Authority spokesman Gerry Carpenter said that while their buses struggled with delays like most other motorists, Thursday was a good day to take public transportation. The number of riders was so high that an additional FrontRunner route was added to both Ogden and Provo.

"If there was ever a day to ride the train, this was it," Carpenter said. "Those who rode the train got to work faster than everybody else."

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