Major Pattern Shift Ahead in the Nation’s Capital

This past week has featured some of DC’s coldest December weather in recent memory.  Friday’s high temperature of only 31° at National Airport was the coldest during the first half of December since December 14, 2010 (29°).  Washingtonians also experienced the first measurable December snowfall this month since 2013. 

December’s monthly average temperature is only 0.6° colder than average through December 16.  That’s because temperatures were above average during the first seven days of the month.  Then from December 8 – 15, high temperatures were colder than average on all but two days.  So far this month, the Nation’s Capital has had three days with high temperatures in the 30s, compared to an average of just under five such days dating back to 1993.  Also, Washington, D.C. has averaged approximately one December day with high temperatures at or below freezing since 1993.  

DC residents saw 1.5” of snow on December 9 followed by another 0.2” on December 15.  By comparison, Washington, D.C. didn’t see its first inch of snow last winter until January 30.  For those of you who are tired of the cold and the snow, several days of milder than average temperatures are on tap during the upcoming week.

Does a sustained period of colder than average weather in the DC Metro Area in December foreshadow similar weather during the rest of the winter?  For example, NOAA data indicates that December 2000 and December 2010 featured 11 and 13 days, respectively, where high temperatures remained below 40°.  Both months finished more than five degrees colder than average, however, the entire winter seasons had below average snowfall.  On the other hand, the months of December 1995 and December 2002 were similar in that they were also colder than average with measurable snowfall.  However, the 1995-1996 and 2002-2003 winter seasons each rank among the snowiest on record in Washington, D.C. 

Washingtonians experienced their warmest December on record just two years ago and that was followed by an epic snowstorm on January 22-23, 2016.  So, while monthly or seasonal weather trends can give a broad overview for a particular area, they often obscure a handful of really warm or cold days and the presence of a large winter storm.  

The upcoming work-week will be similar to the first week of the month in the Nation’s Capital, with several days expected to be in the 50s to near 60° in spots with no significant precipitation expected.