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Probability of a White Christmas: 68%. Likelihood of a White Christmas: 100%

Snow covers Oswego.  A month of unusually heavy early winter snow makes it all but certain the region will enjoy a white Christmas.
Snow covers Oswego. A month of unusually heavy early winter snow makes it all but certain the region will enjoy a white Christmas.

There’s a difference between what’s probable and what’s likely.  The prospect for a white Christmas in Oswego County is a fine example.

This past week, Cornell University’s climatologists predicted that Oswego would have about a 68% chance of having a white Christmas.  They define that as the probability of there being 1 inch or more of snow on the ground on December 25.

But you could be forgiven for wondering whether the good people of the Cornell climate center ever stick their heads out of their windows.

We’ve received an unusually large amount of snow for December and it’s still with us.  Unless Congress repeals winter and installs heat lamps throughout the region, we’re very likely to have plenty of snow on the ground come Christmas Day.

And that, says Cornell climatologist Jessica Rennells, is the difference between what’s probable and what’s likely.

“What we do is look at the past history of snowfall on Christmas day,” Rennells said.  “We look at the past 50 years.”

Add it all up and you get the probability, based on the past, of a white Christmas.

“It’s just the historical data,” she explained.  “You guys already have so much snow.

“People are going to say that their chance of snow (on the ground) Christmas morning are probably higher than that.”

In other words, Cornell says that, based on the past, a white Christmas is probable about 2/3rds of the time.  But, looking forward, a white Christmas is nearly 100% certain.