Explaining how ice storms form

Special Reports

NASHVILLE, Tenn. (WKRN) —  To understand how an ice storm or freezing rain occurs, you need to look at the vertical profile of the atmosphere and how cold subfreezing air may relate to warmer air aloft.

If the air is below freezing aloft and extends down to the near the surface, the precipitation will fall as snow.

how ice storms form
(Graphic: WKRN)

HOWEVER, if there is a very shallow area of 32 degrees or below temperatures with warm air right above it. The precipitation will fall as rain. But then it freezes on contact with the ground and other solid surfaces that are below 32°.

This can often happen ahead of a warm front advancing into a frigid arctic air-mass, but can also occur with cold fronts, as well.

Of course, ice is the hardest of all winter weather precipitation to drive on. But one of the worst aspects of an ice storm is the ice clinging to the trees and power lines bringing them down and leaving people without power during a winter storm.

ice on the Plateau

The most recent ice storm of note occurred February 21-22, 2015. It affected the Cumberland Plateau the most where an inch of ice accumulated on the trees and power lines, bringing them down and leaving 35,000 people without power, along with blocking roads and highways. It was considered the “worst natural disaster in the history of Cumberland County”, according to Cumberland County Emergency Management.

Most people in Middle Tennessee, including Nashville, remember the terrible ice storm in February 1994. It sounded like a war zone outside with trees cracking and hitting the ground and houses. Some folks in Nashville waited almost a week for electric power to be restored. Some areas west of Nashville, especially in Cheatham County waited up to three weeks

The old-timers all remember the great ice storm of 1951 in late January through early February. Ice was followed by snow, totaling 8 inches. Numerous people were left without power. Miles of power and telephone lines had to be re-strung. Roofs collapsed because of the weight of snow and ice.

In addition, gas and oil furnaces expended their fuel, forcing Nashvillians to seek alternative means of heat. And to exacerbate the problem, there were threats of floods as rain-swollen creeks spilled over their banks due to the excessive precipitation.

The News 2 StormTracker team is taking a closer look at new plans and upgraded tools for winter weather preparedness. See special reports all day Wednesday, Nov. 13th in every newscast.

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