With last weekend’s October Nor’easter getting the 2011-2012 snow season off to an early start, the question naturally arises…Does this early snow indicate we’re in for a snowy winter? Since official snow records started in Baltimore back in 1883, there have been 15 Octobers (before this year) with at least a trace of snow. In the winters following those 15 Octobers, the average snowfall was just 19.3″. That’s actually a little below the most recent 30 year normal of 20.2″ and also below the average snowfall for the entire period of record, which is 21.9″.
The snowiest winter following an October snow was the winter of 1890-’91 when 35.9″ of snow fell. The least snowiest winter following October snowflakes was the winter of 1972-’73 when just 1.2″ of snow fell in Baltimore.
The dominant climate signal for north America this winter is expected to be La Nina (cool waters in the tropical Pacific Ocean), which does not give us a clear indication for what to expect. So, our winter weather will be largely controlled by the North Atlantic Oscillation (NAO). The NAO is the alternating pattern of high and low pressure over Greenland and the North Atlantic Ocean. When high pressure builds up in this area, cold Canadian air is shunted south into the northeastern and mid Atlantic regions of the United States. When low pressure develops over the north Atlantic Ocean, the cold air over Canada is swept east before moving this far south. When the cold phase of the NAO coincides with a storm on the coast, the mid Atlantic and northeast can have some big snowfalls. The official 90 day outlook from the National Oceanic and Atmospheric Administration calls for equal chances of cold or mild weather around here, and equal chances of wet or dry conditions.
In other words…stay tuned!