Dangerous Winter Storm Pounds Georgia and South Carolina

A historic Southeast U.S. winter storm is pounding Georgia and South Carolina with heavy snow and thick coatings of freezing rain. Car crashes on icy roads from the storm have already killed six people--four in Texas, and two in Mississippi--and travel will be extremely dangerous over much of the South on Wednesday. As of 9 am EST on Wednesday, freezing rain amounts as high as 1/2" had already been observed in Central South Carolina near Columbia. Freezing rain rates as high as 0.1" per hour are expected along a swath from Atlanta, Georgia to the northeast coast of South Carolina. Over 1" of ice may accumulate from freezing rain in areas near Augusta, Georgia. Strong winds will combine with the freezing rain to blow down trees and power lines, and the Sperry-Piltz Ice Accumulation Index rates the potential impacts from areas which receive at least 3/4" of ice accompanied by winds in excess of 15 mph at a 4 on a scale of 1 to 5. At this level, expect "prolonged and widespread utility interruptions with extensive damage to main distribution feeder lines and some high voltage transmission lines/structures. Outages lasting 5 - 10 days." As of 9:45 am EST, 78,000 customers in Georgia had lost power, and power outages were increasing at a rate of 30,000 customers per hour. About 30,000 customers had lost power in South Carolina.


Figure 1. Predicted snow amounts and freezing rain amounts for the period ending at 7 pm EST Thursday, February 13, 2014. Image credit: National Weather Service Southern Region.

Atlanta shuts down for snow and ice
Atlanta, Georgia, which was shut down by the 2.6" of snow Winter Storm Leon brought to the city on January 28, has been shut down again on Wednesday by Winter Storm Pax. Downtown Atlanta had already received 1/2" of sleet and 1/4" of freezing rain as of 7:30 am EST, making travel dangerous or impossible. Up to 1/2" of ice and 3 - 5" of snow are predicted for the city; Atlanta has only had seven snowstorms in its history greater than 4". The 7 am EST weather balloon launched from Atlanta iced up too much and was lost at about 630mb (12,500'). They decided not to launch another one, since it would probably suffer the same fate. The sounding showed a classic freezing rain profile: temperatures near freezing at the surface, cooling to 24° at 2600', with a a 3000-foot thick layer of warm air above that, peaking at a temperature of 38°. That thick layer of cold air above the surface is supercooling the rain as it falls though, allowing the rain to freeze at impact even if the surface temperatures are 33°. One positive aspect: the ice from this storm will melt out rather quickly compared to previous historic Southeast U.S. ice storms. High temperatures are expected to warm into the lower 40s by Thursday and lower 50s by Friday across South Carolina and Northern Georgia.


Figure 2. Atlanta shut down: At 9 am EST on Wednesday, February 12, 2014, the normally busy lanes of I-75 in Atlanta near the I-285 interchange were deserted. Image credit: Greg Diamond, TWC.

Heavy snow for the Mid-Atlantic and Northeast coast Wednesday night and Thursday
The storm will move up the Eastern Seaboard Wednesday night into Thursday, likely bringing six or more inches of snow to major East Coast cities, including Washington D.C., Baltimore, New York City, and Philadelphia. However, depending upon the exact track of the storm, rain may mix with the snow near the coast on Thursday afternoon, potentially keeping snowfall amounts under six inches in New York City and Philadelphia. The winds from the storm are not going to be strong by Nor'easter standards, and only minor coastal flooding is expected. In Philadelphia, where 6 - 10" of snow are predicted, the storm could set a bit of history. If Philadelphia International Airport receives 6 inches or more of snow from this system, it would be the first time since record keeping began during the winter of 1884 -1885 that Philadelphia has had four separate six inch or greater snowstorms in a winter.

Historic U.S. ice storms
Today's ice storm is likely to be more damaging than the January 2000 ice storm, which caused $48 million in losses in north Georgia. However, it will not compare to the damage from the most expensive ice storm in U.S. history, the great February 1994 Southeast U.S. ice storm. That storm killed nine people and caused $4.7 billion (2013 dollars) of damage in portions of TX, OK, AR, LA, MS, AL, TN, GA, SC, NC, and VA. At least 2 million customers were without electricity at some point, and 1/2 million were still without power three days after the storm. Hardest hit was Northern Mississippi, which was deluged with 4 - 5" of freezing rain that created flooding problems. Ice thicknesses of 3.5 - 5.5 inches were common in the state, causing catastrophic damage estimated at $3 billion. Some residents were without power one month after the storm.

TWC has put together a Top Ten Worst U.S. Ice Storms list, and the 1994 storm ranks as the South's worst ice storm. The record for greatest accumulation of ice in the U.S. occurred during the New Year's ice storm of January 1 - 3, 1961, in Northern Idaho, with up to 8" of ice.

Jeff Masters