Winter storm Cleon has already caused widespread heavy snow and below-zero temperatures in the west. As it heads east, it promises to produce the most dangerous of all winter weather phenomena: freezing rain.
Cleon’s Freezing Rain: Areas Affected
As temperatures drop below freezing tonight in parts of Texas, Arkansas, Tennessee, Kentucky, Missouri, and Mississippi, freezing rain will develop in a band that includes Dallas, Little Rock, and Memphis. Superslick roads will be common even in areas that receive only a fraction of an inch of freezing rain; the weight of heavier amounts of ice will cause power lines to fall and tree limbs to break. In parts of the affected area, up to an inch of ice will cause major power outages and travel disruptions.
What Causes Freezing Rain?
Freezing rain falls only when the vertical temperature structure is within a narrow range. There must be a layer of warm air above the ground so that the precipitation is in the form of rain and not snow. Near the ground, there must be a shallow layer of below-freezing air, which freezes solid surfaces. Liquid raindrops can survive a short trip through the freezing air in a supercooled state — they are still liquid. When the liquid drops encounter a solid object, however, they immediately freeze.
If the warm air layer is too shallow or not warm enough, the precipitation will be all snow; if the cold layer near the ground is too wide, the raindrops will freeze and fall as sleet; if the surface air doesn’t get cold enough to freeze the ground, the precipitation will be all rain. The Goldilocks zone of freezing rain occurs in a narrow band between all snow or sleet on one side, and all rain on the other. Its exact location is notoriously hard to predict.
Why is Freezing Rain So Dangerous?
Freezing rain is the deadliest kind of winter precipitation for two reasons:
- Freezing rain is heavy and can break tree limbs, power lines, and even the roofs of buildings.
- Freezing rain is virtually invisible and impossible to drive on. The former is not good for anybody; the latter may be good for auto body repair shops and towing companies, but it is the bane of drivers. Even a tiny fraction of an inch of freezing rain makes controlling a vehicle nearly impossible.
Where is Freezing Rain Likely to Occur?
The United States heartland is a prime location for freezing rain, as cold air from Canada wedges beneath warm, humid air from the Gulf of Mexico. The ideal conditions for freezing rain occur when nighttime cooling coincides with the push of cold air under the warm. This evening and tonight, those conditions will exist in the zone from Texas to Kentucky.
Who’s Next in Line for Dangerous Icing?
The cold air over the middle of the country and the warm air in the southeast are not going anywhere for a while. The conditions for freezing rain will persist through Monday in a band from Texas all the way to New England. If you are in that band, have a generator handy — or at least know which neighbor has one.