While working as a forecaster at the Indianapolis NWS Office in the 1970s, the computer models were getting good enough to extend a forecast out about seven days. For the most part, they were fairly accurate through seventy-two hours. We applied a number of what was known as cook book rules in forecasting snow amounts. Many are still basic enough to use today.
One of the standard synoptic forecasting techniques was to expect the heaviest snow to accumulate about 150 miles north of the track of the center of lowest pressure. That was close to the case for last Saturday’s snowfall of six inches from Clear Lake, Iowa to Cumberland, Wisconsin.
Looking out at the long range GFS, I can’t find a system that has the potential to produce signifcant snow in the Upper Midwest between now and December 24th. But I’m experienced enough to doubt model output data after five days, particularly in the winter months. I know this much, daylight is continuing to grow short and we are gradually approaching the historically coldest days of the season.
Our friends at the State Climate Office have posted this graphic of the probability of a White Christmas in Minnesota. Here’s a statement they included with the image; The best chances of having a white Christmas is almost guaranteed in the Boundary Waters Canoe Area and a good part of the Arrowhead. The chances decrease to the south and west and the best chance for a “brown” Christmas is in far southwest Minnesota where chances are a little better than 60%.
You can dive into more details of their research by clicking on their White Christmas post.
Cold air is still coming, but so is the moderation. Once we get through the next forty-eight hours of winter chill there will be a nice bump-up in temperatures for Saturday afternoon through Sunday.
The GFS has been consistent with readings in the lower to perhaps the middle 30s on Sunday. Here’s a snapshot of expected surface temperatures and winds for noon on Sunday.
Before I turn the weather fun back to the Chief meteorologist, Paul Huttner, I’ll leave you with this extended temperature outlook for the next 8 to 14 days from NOAA’s Climate Prediction Center. I’ll not include an editorial comment.
This is not a magnitude of warmth or cold but a confidence level of above or below normal temperatures. May the wind be always at your back.