The ice storm underway in the South is going to be one of the most damaging such storms in decades, if current projections are realized. The storm, which is gathering strength along the Gulf Coast, is pushing warm, moist air up and over a cold dome of high pressure that is keeping temperatures below freezing at the surface from Maine to Alabama.
Ice more than an inch thick is expected to coat much of central and eastern Georgia into central South Carolina. This may not sound like much, but considering that tree branches will break at just a quarter to a half-inch of ice accumulation, this event is bringing so much ice that entire trees and power poles are likely to come crashing down in the hardest hit areas.
See also: How to Track the Historic Ice Storm
Freezing rain results when a layer of warm air aloft and cold air at the surface causes rain to fall and freeze upon contact with the ground. On Wednesday, a strong area of high pressure across New England is funneling cold air all the way down the East Coast and into Georgia, in a phenomenon that weather forecasters call “cold air damming.”
In an ominous sign, meteorologists at the National Weather Service (NWS) office in Atlanta have run out of adjectives to describe this event, writing in an early morning forecast discussion:
“This is an event of historical proportions!! Catastrophic...Crippling… Paralyzing… Choose your adjective. This is a very very big deal especially from metro Atlanta east along the I-20 corridor… generally anywhere south of I-85 and north of I-16 where the most significant ice totals are forecast. Stay safe out there!”
In order to improve the reliability of the computer models that its forecasters use to predict the weather, the NWS tasked the famed U.S. Air Force Reserve Hurricane Hunters to fly a reconnaissance mission above the Gulf of Mexico last night. The aircraft dropped instrument packages known as dropsondes, which sent back data on air temperature, pressure, and winds, among other information. This data was then fed into an overnight run of one of the main computer models.
“The U.S. Air Force Hurricane Hunter made five different drops in the Gulf of Mexico last evening,” NWS spokesman Chris Vaccaro told Mashable. “The purpose was to collect additional observations over the Gulf to better assist with [the] track and intensity [forecast] of the winter storm.”
Such a flight is not standard operating procedure for most storms, demonstrating that the NWS views this event as particularly serious. “I do not recall when the last time was that we used these types of aircraft observations for an East Coast storm, but we have in past for potential high impact events,” Vaccaro said in an email message.
USAF Hurricane Hunters flying winter storm recon mission over Gulf of Mexico 2nite obtaining vital atmospheric data. http://t.co/uXkGGcSAiL
— NWS New York NY (@NWSNewYorkNY) February 12, 2014
 
After the flight and the computer model data that came in early on Wednesday, the NWS forecast office in Atlanta increased its forecast ice totals from about an inch to more than an inch.
Forecasts call for an inch or more of ice accumulation in an arc from southeast of Atlanta to Columbia, S.C., and on up to Raleigh, N.C. Such a large accumulation of ice is almost certain to cause extensive damage to trees and power lines.
Based on an experimental index of ice storm severity, known as the Sperry-Piltz Ice Accumulation Index, this storm is likely to rank at a level 4 out of 5. A level 4 ice storm can cause “prolonged and widespread utility interruptions” that last at least five to 10 days.

Already, the freezing rain has resulted in at least 200,000 people losing power across the South and Southeast, a number that is expected to climb rapidly throughout the day on Wednesday and into Wednesday night. A less severe and widespread ice storm in the Southeast in 2000 caused more than 500,000 to lose power in Georgia alone.
In addition, the tree damage from this event could be so significant that it is visible for many years, much as a 1998 ice storm caused widespread tree damage and blackouts across northern New England and Quebec.
The ice is not the only threat from this storm. Heavy snow will also fall to the north of the zone of freezing rain, where the cold air layer is deeper.
The storm is projected to move northeastward along the East Coast, blasting Washington, Baltimore, Philadelphia, New York, and Boston with several inches of snow followed by a sloppy mess of rain and sleet. To the west of the big cities, across the Appalachians, more than a foot of snow may fall.
However, if the track of the storm changes by as little as 30 miles, the zone of heaviest snow will shift. This could make the difference between a foot of snow in Washington and just six inches, which is the current forecast.