Will the dream of a Chicago white Christmas come true?

Chicago - The official winter forecast from the National Weather Service is calling for a relatively mild winter with less snowfall than average. Despite that, it only takes an inch of snow on the ground on Christmas Day for it to be declared an official "white Christmas". 

Will we have a blanket of white on Christmas Day this year? It is way too early to make a definitive forecast for snowfall on or before Christmas morning, but there are some clues we can collect to give us a better idea of what lies (or doesn't lie) ahead on the ground for the holiday.

Based on climatology, the odds are against us for having a white Christmas. The probability of Chicago seeing one is about 35%, so about two out of three Christmases are typically not of the white variety. 

The further north you go in our country or the higher in elevation, the better the chance of seeing significant snow on the ground for Christmas.

The further north you go in Illinois, the greater the chance too. Our far northern and northwest suburbs have about a 40-50% chance of seeing a white Christmas. The probabilities drop to 25-40% in the suburbs well south of the city. 

Even with the forecasting favoring less than ideal conditions this winter for big snow, it only takes one storm at the right time to give us enough snow for a white Christmas classification. Last year is a good example.

 The "Accumulated Winter Season Severity Index" or AWSSI (or "misery index") calculated by the Midwest Regional Climate Center measures our winter misery and assigns it a category. The categories in order from least miserable to most include mild, moderate, average, severe, and extreme. Last year's winter was rated "mild". We had almost half the normal snowfall we typically see. Even still, we managed to squeeze out enough snow in time to have that somewhat elusive white Christmas.

2022 saw the first white Christmas for Chicago in five years. Here are some recent white Christmases we have seen in Chicago and the amount of snow on the ground for each:

• 1" on December 25, 2022
• 2" on December 25, 2017
• 2" on December 25, 2016
• 2" on December 25, 2010
• 2" on December 25, 2002

Most of the longer-range models seem to suggest it could be a tough year for fans of white Christmases.

The longer-range temperature outlooks from the Climate Prediction Center are hinting at a milder and drier-than-average pattern developing soon that could continue up to and possibly right through Christmas.

The 6-10 day temperature outlook has northern Illinois and Indiana near normal overall. Average highs for that time of the year are around 37 to 38 degrees. Not ideal for snow production but lows normally drop into the middle 20s. 

This forecast covers the period from this Sunday through the following Thursday.

The precipitation forecasts aren't boding well. The 6-10 day outlook precipitation outlook that covers next Tuesday through the following Monday, has us near normal. The problem is, this could be the beginning of a switch to a drier pattern. More on that below.

The 8-14 day temperature outlook has us "likely above" average overall. This takes us right up to the beginning of the week before Christmas. 

The 8-14 day precipitation outlook has us "leaning below" average overall. This takes us right up to the beginning of the week before Christmas. 

So, in summary, we are moving towards a potentially milder and drier pattern leading right up until about seven days before the holiday.

The 3-4 week temperature outlook covers the period from a little more than a week before Christmas to about a week after the holiday. It keeps the relatively mild pattern coming, favoring us for above-average temperatures overall.

The 3-4 week precipitation outlook forecasts for most of us equal chances of above or below normal precipitation. It favors our far northern suburbs slightly for above-normal precipitation.

The monthly temperature outlook for December seems determined to keep snowfall below average. The forecast calls for temperatures to be "likely above" average overall for the month. Not the type of forecast you would hope for if a white, rather than wet, Christmas is your goal.

The good news for those who want a white Christmas is that these forecasts are not guaranteed. They will change, no doubt. Plus, timing is everything. We just need the right combination of cold temperatures and enough moisture to fluff up an inch of snow on the ground by the time Santa is done with his big ride this year.