Well, you may not have to dream much longer - we're going to have a couple rounds of snow this week. The greatest chance of a White Christmas will come on Christmas Eve into Christmas Day, where a powerful cold front and low pressure system is expected to push through the region. A White Christmas is defined as having at least 1" of snow on the ground on Christmas Day.

Historical probabilities of a White Christmas. 

According to the National Weather Service (and climate.gov), the Erie region has a 51-75% of having a White Christmas any given year.

For this Christmas, I am currently expecting a 70% chance of a White Christmas given the current forecast and model predictions. At this point, based off from all of the data available, there is a currently a higher chance of having snow on Christmas Day than not having snow on Christmas Day for 2020.

So, just why am I gloating a 70% chance? First, it is worth noting that I initially issued a 70% chance on 12/18 - keep this in mind as you read the following. The weather community began to monitor the potential of a powerful storm that is expected to arrive around Christmas Eve since the end of last week. At the beginning, we started to monitor ensembles which are essentially weather models that are ran multiple times with slightly different input values.

One weather model that we watch is the ECMWF (the "Euro") model. There are two things to watch here. The first graphic I have is the probability of the snow depth over 1 inch of snow. This is different than the probability of new snow accumulation being over one inch. Notice in this graphic, Erie would have the probability of about 90% of having greater than 1 inch of snow.

ECMWF probabilities of having snow depth over one inch. - WEATHERMODELS

Additionally, let's also look at the probability of having over 1" of new accumulation.

ECMWF probabilities of having new snowfall over one inch. - WEATHERMODELS

As you can see, a lot is the same but this is for additional snowfall ending Friday morning. So, there are very high probabilities of having over 1" of new snowfall for Christmas morning. Now, if we're wanting to see probabilities for having over one inch of new snow accumulation - we can look at that as well. Erie, currently, has about an 85% chance of having over 3" of new snow by Friday morning - which would definitely put us in the contention of a White Christmas.

ECMWF probabilities of having new snowfall over three inches. - WEATHERMODELS

I hope you have found this thought process helpful when understanding the rational behind saying a "70% chance of a White Christmas." Do I think the possibility is greater than 70%? Yes, I do, but as of right now there's still more details that need to be worked out before I would feel comfortable raising my probability.