Meteorological winter is here and the first half of December has seen it’s ups and downs in the weather department. In particular, the Midwest has been fairly quiet, while an active pattern has dominated the Northeast… with even a large winter storm dropping feet of snow from Upstate NY into Massachusetts on December 1st – 3rd. While winter weather has kept many busy out East, the pattern has been generally unfavorable for long-lasting cold as thunderstorm activity in the tropics continues to remain focused over the Indian Ocean (which is not conducive for cold in December). Basically, the Midwest into the Northeast has been relying on high latitude blocking over Greenland and Alaska to bring brief shots of cold air. This blocking has helped to stave off milder weather at times, however, enough cold air has still been around at just the right time to create a few winter storms.
This less than optimal winter pattern will likely continue through the week of Christmas, but after that a gradual change to colder and colder weather will begin. This slow change will be aided by two large scale changes. The first will be tropical thunderstorm activity increasing over the warmer than average water in the western/central Pacific as we head into January. This positioning (believe it or not), puts forcing on the atmosphere that favors cold air over the northeast quarter of the country. Second, a stratospheric warming event will likely occur around a week or two from now, which correlates with more Greenland/Alaskan blocking that brings arctic air and stormier weather to the East. The combination of these two events will likely allow for more sustained cold into January 2020 along with an increasing risk for more frequent winter storms. Cheers to potentially snowy 2020!