The 1993 North American storm complex, also known as the '93 Superstorm or the [Great] Blizzard of 1993, was a large cyclonic storm that occurred on March 12- 14, 1993 on the East Coast of North America. In most locations, it was a heavy snowstorm.
This storm complex was, by all accounts, massive, affecting over 26 U.S. states and much of eastern Canada. Bringing cold air along with heavy precipitation, it was manifest as a blizzard over much of the area it affected. The storm brought snow as far south as northern Florida, thundersnow from Texas to Pennsylvania, and whiteout conditions. Some affected areas saw more than 3.5 feet (1.0 m) of snow, and snowdrifts were as high as 30 ft (9.5 m). Southern Florida saw no snow, but tornados and derechos, resultant from the storm, occurred there and on Cuba. Responsible for 300 deaths and the loss of electric power to over 10 million, it is purported to have been directly experienced by over 130 million people in the United States, about half the country's population at that time. Every airport from Halifax, Nova Scotia to Atlanta, Georgia was closed for some time because of the storm. The volume of the storm's total snowfall was later computed to be 12.91 mi3 (53.96 km3), an amount which would weigh (depending on the variable density of snow) between 5.4 and 27 billion tonnes.
Temperatures accompanying the storm were unseasonably cold for early spring: average daily maximum temperatures, in mid-March, are around 46°F (8°C) in Boston, 51°F (11°C) in Philadelphia, 65°F (18°C) in Atlanta and Texas. During the 1993 storm, these places were all near or below freezing, and parts of New England saw daily maximum temperatures as low as 14°F (-10°C). Record low temperatures for March were recorded in much of the Southern U.S.
Barometric pressures recorded during the storm were also unusually low: readings of 28.35"Hg (960 mb or hPa) were observed in New England. Usually, such low readings are observed only in hurricanes, which peak at the exact opposite time of year. It also pushed a storm surge ashore on the Florida panhandle, drowning a few people taken by surprise at the storm's ferocity. (This incident is featured occasionally on reruns of Storm Stories.)
As one of the most powerful storms in recent history, the storm has been described as the "Storm of the Century" by many of the areas affected. The last blizzard to have such an effect on the Southeast was the Great Blizzard of 1899.
Weather forecasters saw only shortly in advance of the storm that it would be extremely powerful, noting a confluence of factors said to occur about once in 500 years. A "disorganized area of low pressure" that formed in the Gulf of Mexico (which, being warm by March, is a frequent source of spring snowstorms) joined an arctic high pressure system in the Midwestern Great Plains, brought into the mid-lattudes by an unusually steep southward jet stream. These factors combined to produce unusually cold temperatures across the eastern half of the United States. A cyclonic low pressure system from Nova Scotia (see: nor'easter) later collided with these airmasses, producing the storm, which gained strength as it moved northward.
Weather forecasts early in the week did not expect much from the system at all, which made the storm all the more shocking when it did arrive. Atlanta forecasts thought there would only be a few rain showers by that weekend, but it later dumped 4 to 8 inches or 10 to 20cm of snow on the city, several times what it normally receives in a winter. To the north and west, cities like Birmingham, Alabama and Chattanooga and Knoxville in Tennessee were buried by double or triple that amount, even further beyond what was initially forecast. Isolated areas of even heavier snow occurred due to thunderstorms.
The weight of record snows collapsed many factory roofs in the South, and snowdrifts on the leeward sides of buildings caused a few decks with substandard anchors to fall from homes. Hundreds of people were rescued from the Appalachian Mountains, many caught completely off-guard on the Appalachian Trail, or visiting cabins and lodges just to see what they expected would be a much lighter snow. The heaviest snow recorded was at Newfound Gap, where U.S. 441 crosses the Tennessee and North Carolina border, with five feet or 1.5 meters, plus drifts. Electricity was not restored to many isolated rural areas for a week or more.