Wednesday, December 14, 2022

Prospects of a White Christmas in central Indiana this year

A lot of people starting to ask about the prospects of a White Christmas in central Indiana.

Meteorologists define "White Christmas" as having 1" of snow on the ground at 7am December 25.  Historically, Indianapolis has had a White Christmas 28% of the years since 1899.  The last White Christmas was 2017 and the city has only had it two out of the last 17 years.  So you could say we are overdue for snow Christmas morning.

Let me just say that it too early to say with any certainty if there will, or won't be, snow on the ground for Christmas.  Considering it takes just a few hundredths of an inch of liquid to produce 1" of snow (when it is very cold), it is impossible to forecast this far in advance.

That being said, I have taken a closer look at the long range global computer model ensembles.  Specifically, the ECMWF, GFS, and the CMC.

If you don't know, computer model ensembles are a combination of computer model runs.  Instead of running just a single forecast, the computer model is run a number of times from slightly different starting conditions. The complete set of forecasts is referred to as the ensemble, and individual forecasts within it as ensemble members.

The three ensembles - ECMWF, GFS, and CMC - result in a total of 100 different forecasts, or ensemble members.  Out of the 100, 75 members suggest there will be at least 1" of snow on the ground 7am December 25.  It should be noted that is a 6.3% decrease from Tuesday night's runs.

The images show the various members of the ensembles.

Keep in mind this is just one instance of runs.  This is going to, and likely will, change every six hours as more data becomes available.

One thing that is looking more and more likely is a blast of cold air coming to the Midwest late next week.  For more on that, visit my FB page and scroll down to the previous post.

Let me know what you are hoping for Christmas.  A White Christmas or not.

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