December 2020 Forecast Update

NOAA's Climate Prediction Center issued their December 2020 forecast update which features some changes to the temperature and precipitation forecast. Overall, December may average out to be a warmer than normal month with less than normal precipitation. The winter as a whole (December-January-February) still features uncertainty with respect to temperatures (though as Bill Marino pointed out recently we may see periods of abnormally warm and cold temperatures that average out to near normal), but precipitation odds are still tilted toward wetter than normal (both rain and snow). Below are the latest graphics for December only:

Temperature

Precipitation

Why is December looking milder and drier?

The Climate Prediction Center has observed a few important changes. While La Niña is alive and well across the Pacific Ocean, there are some important factors that the long-range forecasters have noted:

• The presence of a mid-level ridge initially expected over the Gulf of Alaska has shifted eastward from previous expectations
• Increased ridging over the north-central U.S. supports warmer and drier than normal conditions as opposed to an active jet stream bringing more weather systems to the region, increasing our risk for winter storms and/or lake effect snow
• The latest GFS and ECMWF ensemble forecasts for December are showing drier and warmer than normal for the Great Lakes for at least the first half of December

There may be more reasons that have yet to surface. What is certain is that La Niña hasn't gone anywhere and still is a reasonable seasonal predictor of weather patterns, but it can be overruled by other teleconnections or other factors. These are difficult or impossible to anticipate months in advance. Winter may take longer to get going this time around, as has happened several times since the strong winters of 2013-2014 and 2014-2015. We will continue taking a look at things and see what Mother Nature decides to throw at us for the 2020-2021 winter.