Will Pittsburgh See a White Christmas this year?

Merry Christmas to all, first off! Hope everyone enjoys a great day spent with family and friends while remembering the real reason for the season! One important question on everyone’s mind today is “Will there be a White Christmas this year?” Let’s start at the basics to answer this question.

Definition of a White Christmas

I heard earlier this week that some local news stations had conflicting definitions over what a “White Christmas” was. Some claimed that to “get” a White Christmas, an inch of snow needed to fall. This is not true, nor do I believe it will be the case in the Pittsburgh region tomorrow (on Christmas day). According to the NCDC, or National Climatic Data Center (a part of the National Weather Service), a White Christmas is defined as a location having one inch or more of snow on the ground at that particular location. I’ll trust the NWS on this one.

What's the likelihood then?

In Pittsburgh, we have a 33% likelihood of seeing a White Christmas, based on the NCDC’s climactic data records. Other cities around the state have somewhat higher probabilities, with Bradford clocking in with a 70% chance (Erie was next in line, with a 57% chance). The first image below shows the probability of a White Christmas (in percent likelihood) across the United States. An interesting fact did appear on Wikipedia, stating:

According to research by CDIAC meteorologist Dale Kaiser, the United States during the second half of the 20th century experienced declining frequencies of White Christmases, especially in the northeastern region.

Meanwhile, the NCDC paper (links to both sources at the bottom of this post) says that most of New England (and points westward along those parallels) have a 60% or better chance, generally.

As for Christmas 2010, it’s safe to say we’ll have a White Christmas in Pittsburgh. Almost all areas have a solid inch of snow on the ground, despite a bit of melt off on Christmas Eve due to temperatures getting close to the freezing point. Some areas have seen snow blown around, but overall it should be enough. The second figure below shows the current (as of 12AM 12/25/10) modeled snow depth across the state. During Christmas Day, there will be some flurries to light snow showers across the western part of the state, much as we’ve seen over the past few days. However, I don’t believe it will be enough to make it to a full inch for places that don’t already see it.

One final reminder to close out this article, almost all of the state saw a White Christmas last year, while most of the PA population centers (the southern half of the state, more generally) was snow free on Christmas Day 2008.