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A big winter storm is the atmosphere's mechanism to redistribute heat energymore evenly through the atmosphere. This is accomplished through large-scalecirculations that move cold air masses south and warm air masses north. Thestorm center itself is always found on the eastern side of large upper-airtroughs. Here, differing air masses are in close proximity, and the densitydifferences are what drives the storm's massive circulation. In turn, the airmasses get intricately involved with one another, which ultimately produceslarge scale areas of snow, ice and rain.With the above in mind, the Eastern Seaboard is clearly the perfect place forhuge winter storms. Here, there can be a huge temperature gradient between warmair over the Gulf Stream and cold air across the interior. The most powerfulof these storms are called nor'easters.

The storm coming up the East Coast tonight and Saturday will be one of thosepowerful nor'easters, complete with heavy snow through the interior and stronggales along the coast.

Story By AccuWeather.com Senior Meteorologist John Kocet.