A Warm and Wet December

December 14 - 16, 2018 Rainfall Totals (Source: NWS - LWX)

The first three weeks of December 2018 couldn’t have been more different than last December.  Through December 21, DC’s average monthly temperature (combining daily high and low temperatures) was 2.2° above average.  The final five days of December 2017 were unusually frigid in the Nation’s Capital and remained at 33° or colder.  With a high/low temperature of 23°/16°, December 31, 2017 was also DC’s coldest December day since 1989.  By comparison, DC’s high/low temperature of 67°/47° made for the warmest December day in the Nation’s Capital since December 27, 2016 (68°/49°).  

NOAA’s temperature outlook over the next six to 10 days is for above average temperatures over much of the eastern United States through the end of the year.  That will disappoint local winter weather enthusiasts who were hoping for a “White Christmas.”  There hasn’t been snow on the ground in the DC Metro Area on Christmas Day since 2009.  December 2018 will finish as a warmer than average month.  That’s not unusual considering seven of the last 10 Decembers have been warmer than average in Washington, D.C., including DC’s warmest December on record in 2015.

 

One of DC’s more significant weather headlines this month occurred on December 15 when 2.55” of rain fell at National Airport, breaking the existing 129-year-old record for wettest year.  The 61.33” of rain that occurred in 1889 stood as DC’s wettest year until last Saturday.  DC’s rainfall total since January 1 now stands at 64.75”.

Winter weather enthusiasts might wonder what clues, if any, a warm and wet December offer for the rest of the winter.  Looking at DC’s 10 snowiest winters on record, seven of the 10 Decembers in those winters were colder than average.  That includes December 2009, which featured DC’s largest December snowfall on record with 16.4” of snow on December 18-19.  Six of the 10 Decembers in DC’s 10 snowiest winters were also wetter and snowier than average.  

The fact is, however, that a multitude of factors go into a seasonal forecast.  Winter weather in the United States can be influenced by the presence of El Nino or La Nina and other things like the North Atlantic Oscillation.  December weather by itself isn’t a reliable indicator of what the rest of the winter will feature.  For example, December 1989 finished tied with 1917 as the second coldest on record in the Nation’s Capital – almost 12° colder than average.  It was also a very snowy month with 9”, compared to the December average of 2.3”.  By comparison, the rest of the winter was warmer than average with a combined snow total of only 2.8”.

On the other hand, December 2015 was DC’s warmest on record with no snow.  There was a major shift in the weather pattern by mid-January of 2016 when the right elements came together to produce the epic “Blizzard of 2016.”  That storm made the 2015-2016 winter season snowier than average in Washington, D.C.  Given the warm weather prevalent in the DC Metro Area in December 2015, a snowier than average winter seemed like a pipe dream in early January 2016.  

My colleagues and I on the WUSA9 Weather Team will keep DC Area residents apprised of the latest weather headlines both on-air, online, and on the free WUSA9 app.