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Dreaming of a White Christmas? |
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Maybe not so much after the quick start to the winter season with Rockford being a little over 10 inches away from the snow season (July thru June) normal and Chicago being about 20 inches away. With this active start to the season, folks from the Dakotas all the way into southern Illinois already have some sort of snow cover as of the morning of December 19th. With forecast temperatures over the next week remaining below freezing throughout, this snow pack is not anticipated to diminish much. Coop observers from across northeast Illinois and northwest Indiana report that as much as 10 inches of snow covers the ground up along the Wisconsin/Illinois border, while lower amounts of around 1 to 2 inches coat the region from I-80 southward. Here are the latest snow depth observations from local coop observers:
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The following is an image from the National Operational Hydrologic Remote Sensing Center showing the snow depths across the United States on December 19th.
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A White Christmas is technically defined as having an inch of snow depth on the ground on December 25th, however, others consider it to be a White Christmas if it is snowing on Christmas regardless of whether it accumulates or not. Here is a national map outlining the normal probabilities of having a White Christmas across the United States from the National Climatic Data Center using the one inch snow depth rule.
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The Rockford area is in the 51-60% probability of having a White Christmas, while the Chicago area is in the 41-50% probability of having a White Christmas. The last time that both Chicago and Rockford had an inch of snow on the ground on Christmas morning was in 2003 when exactly 1 inch was on the ground. Last year, Rockford did have an inch of snow depth, but Chicago did not.
There is also an alternate thought where if it snows at all that day, it is considered to be a White Christmas. If you go by this rule, then the last time this happened was in 2005 when a Trace of snow fell at both Chicago and Rockford. The last time that measureable snow fell on Christmas Day was in 2004 when 0.3” fell at Chicago and 0.4” fell at Rockford. Throughout their respective Christmas histories, 54% of Chicago’s and 40% of Rockford’s Christmas have had at least a Trace of snow that fell that day.
The forecast for this Christmas being white is looking almost certain at the moment with the entire region covered with at least an inch of snow with temperatures expected to remain below freezing throughout. There will also be a few more chances for snow through Christmas day, which may add a fresh white coat to the snow pack.
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Updated 12/19/08 TJH
