WHAT EXACTLY IS A WHITE CHRISTMAS
A White Christmas varies from one country to another. According to NCDC, in order for December 25th to be classified as a White Christmas in the United States there must be a 1" snow depth observed Christmas morning. Many though, just look at White Christmas by either snow falling or waking up to a fresh snowpack. From time to time, we may have trouble seeing snow in Indiana but speaking from a statistical standpoint, our odds for a White Christmas in Indiana seems pretty good especially North. Based off of data collected from 1981-2010, there is a 40%-50% probability for Northern Indiana to see a 1" snow depth Christmas morning, 25%-45% probability in Central Indiana, and 10%-25% probability for Southern Indiana. You can refer to the map seen to the right.
Let's break this all down....
The following information was prepared by the National Weather Service Office in Indianapolis, Indiana. Click HERE to be redirected to their original web page.
There are several ways to define a White Christmas. For the purposes of our historical look back, we’ll include a White Christmas as any day that has either at least a trace of snow on the ground, or experiences at least a trace of snow falling that day. In more general terms, we’ll define a White Christmas as any Christmas day that Indianapolis sees snow.
So what is the chance of at least a trace of snow falling at Indianapolis on Christmas day? Well, snowfall records on Christmas day have been kept in the Indianapolis area since 1871. And in that 138 year period of record, a trace of snow (or more) has fallen 62 times. This could be equated to a 45% chance of at least a trace of snow falling on Christmas Day.
Our other possibility for a White Christmas would be if there was at least a trace of snow already on the ground. This could be old snow from a week ago, or just the day before. Snow depth records don’t go quite as far back, and these were started in 1896. And in that 113 year span, there has been at least a trace of snow on the ground on Christmas Day a total of 60 times. This could be equated to a 53% chance of at least a trace of snow on the ground on Christmas Day. The last Christmas that saw snow on the ground in Indianapolis was in 2004, just a few days after a major snow storm produced 1 to 2 feet of snow over central Indiana. Snow did fall on Christmas Day 2005, 2006 and 2009, but due to temperatures in the 30s and the snow mixing with rain, none of it stayed on the ground.
With both of our possibilities for a White Christmas explored, what then is our final chance? What would our probability be of having either a Trace or more of snow falling, or a Trace or more already on the ground? Since 1871, this has happened in a total of 97 times, where either the snow has fallen or already been on the ground. This gives us an overall probability of 70%! Which means that 7 out of every 10 years, on average, will see either some snow falling or some snow already on the ground for Christmas Day.
So if a White Christmas is your dream, then you’ll probably take heart in these numbers. Much more often than not, there will be at least a few flakes around to greet us come Christmas Day!
\Its too early to put out an actual forecast for Christmas Day. The long range GFS models is picking up on a potential storm system shortly before the holiday. Precipitation type isn't clear as the possibility for rain, snow, and/or a wintry mix exists. Temperatures will be cold as well. Here's a look at Christmas high temps over the past 10 years in Indianapolis. THESE ARE JUST HIGHS. In 2011, we had the 20th warmest Christmas Day in 142 years of record keeping. In 1983, the high was -4 after a low of -14. This is the coldest Christmas Day on record. Look for more Christmas Climatology in a future blog.
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