Weather patterns don't stay locked for long

Stephen Letro
National Weather Service Jacksonville
Published Thursday, March 01, 2007

Why has there been so much snow up North this winter?

In a very real sense, folks in the Northeast are paying the price for what had been a very mild early part of the winter. During much of December and early January, while the eastern part of the country was basking in weather up to 10 degrees warmer than normal, the Rockies and Plains states were being pummeled by one storm system after another. At that time, the configuration of the jet stream favored cold and wet conditions in the West, and mild and dry weather in the East.

One thing that we know is that weather patterns rarely stay locked in place for an entire season and sure enough, by the middle of January the pattern flipped, sending storm systems across the southern U.S. into the Northeast and pulling down vast amounts of frigid Arctic air from Canada.

Regions that had averaged 5 to 10 degrees warmer than the long term average earlier in the season were now seeing below normal readings of the same magnitude. What made this change especially brutal was the fact that due to the warm weather through early January, the Great Lakes stayed much warmer than normal. That meant that when the Arctic air came pouring over the Lakes, it was able to absorb vast amounts of moisture off the Lakes, which it then dumped in the form of lake effect snow in the normal snow belt areas.

Such pattern changes are really fairly common during the winter, but this year the changes occurred in an order and in a timing that served to maximize the snowfall potential across much of the country, with wintry precipitation at one point occurring as far south as central and southern Georgia.

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