Changing Seasons

Autumn 2016: One for the Record Books

Meteorological fall, which runs from September 1 through November 30, was an especially warm and dry three-month period in the Mid-Atlantic Region.  In fact, November 2016 put an exclamation point on a record setting fall season in the Nation’s Capital.  The annual rainfall deficit in Washington, D.C. ballooned from 1.47” on September 1 to 6.13” by November 30. Only 4.16” of rain occurred during the fall in Washington, D.C. and that made it the seventh driest autumn on record and the driest since 2001 (2.65”).

The combination of a September that tied for third warmest, the tenth warmest October and a warmer than average November made the 2016 fall season the warmest on record in the Nation’s Capital.  The seasonal average temperature of 63.9 degrees (combining daily high and low temperatures) surpassed the previous record from 2007 by more than half a degree (0.6).  Despite being much warmer than average, there were some cold days this fall such as on November 23 when the low temperature reached 32 degrees at National Airport and 20 degrees at Dulles Airport.

Now that December has begun, what constitutes average weather in the Mid-Atlantic Region?  Average high and low temperatures at National Airport on December 1 are 52/37 degrees and drop to 44/29 degrees by New Year’s Eve.  The winter solstice occurs on December 21 and is the first day of “astronomical” winter in the Northern Hemisphere.  Washington, D.C. averages 3.05” of rain and 2.3” of snow during the month of December based on NOAA’s running 30-year average from 1980 – 2010.

Another interesting December trend in the Nation’s Capital is that since 2000, nine of the last 15 Decembers have been warmer than average.  Some many find that ironic because measureable snowfall has occurred in 10 of the last 15 Decembers.  However, a warm and wet December (such as in 2015) doesn’t always indicate what the entire winter will be like.  For example, while Washingtonians didn’t see their first measureable snow last winter until January 17 (0.3”), the season was still the third consecutive snowier than average winter in the Nation’s Capital.

NOAA’s outlook for December calls for a slight chance of above average precipitation in the Mid-Atlantic Region.  That coincides with some encouraging changes in the weather pattern.   My colleagues and I on the WUSA9 weather team expect an increasing potential for appreciable (and much-needed) rain on Tuesday.  That would be excellent news for the entire DC Metro Region.