Across North America in November 2017 snow cover was above normal for much of the month until later month when warm weather caused a retreat in North-Central U.S. snow cover and also in the far Northeast U.S. Absence of the late month warm pattern may have caused November 2017 to observe near record snow cover. Most recently, the November 2013 and 2014 observations were similar to last month. In each following winter a “polar vortex winter” pattern developed in which the eastern U.S. was cold and snowy. That pattern will be present at times this winter season separated by mild Pacific influence.
The Northern Hemisphere November snow cover was 10th snowiest in the 1966-2017 period of record. The November value is consistent with 6 of the past 7 years. Above normal snow cover in the northern hemisphere prior to the start of northern hemisphere winter is due primarily to the polar vortex forming over still open water of the far northern polar region due to the constricted polar ice cap.
Pictured: Northern hemisphere snow cover in November 2017 according to the Rutgers University Snow Lab.