Snow – A Rare Commodity

 

January 2016 Blizzard, Bethesda, MD

Three of the last four winters have had dramatically below average snowfall in the Nation’s Capital.  Last winter, for example, a seasonal total of only 0.6” occurred and was DC’s third least snowy winter on record.  It’s remarkable that Washington, D.C., which averages 15.4” of snow annually, hasn’t had an inch of snow since February 2019.

December is DC’s third snowiest month of the year on average with 2.3”.  However, every December since 2010 has had below average snowfall in the Nation’s Capital.  Not since 2017 have Washingtonians even had an inch of December snowfall.  That’s what makes this week’s winter storm potential especially dramatic.

Winter’s tend to be cyclical in the DC Metro Area with several snowier than average followed by some that feature below average snowfall.  Washingtonians experienced three consecutive snowier than average winters between 2013-2014 and 2015-2016 for the first time since the late 1970s.  However, the last few years have been disappointing for DC Area winter weather enthusiasts with only scant amounts of snowfall.

The National Weather Service keeps weather records at DC’s two major airports, National and Dulles.  The first inch of snow occurred in December twice in the last decade at National Airport, while Dulles had its first inch in December four times.  Last winter was unique in that less than 1” occurred during the entire winter.  Winter weather can be fickle in the DC Metro Area.  March was actually the snowiest month of the year during five of the last 15 winters.  DC’s first inch of snow during the 2012-2013 winter didn’t occur until March 25 (1.4”)!

A lot of attention is given to seasonal weather forecasts and whether temperatures and precipitation will be above or below average.  Some factors that meteorologists look at when issuing winter weather outlooks include the ENSO status (the presence of El Nino, La Nina or neither), and the status of the North Atlantic Oscillation (NAO), etc.  The positive or negative phase of the NAO is based on sea level pressure differences between the semi-permanent features, the Azores (subtropical) High and the Subpolar Low.  NOAA’s winter weather outlook for the DC Metro Area is for warmer than average temperatures with near average precipitation.

Irrespective of the overall seasonal weather outlook, the right ingredients only need to come together once to create a significant winter weather event.  That’s what happened during the 2015-2016 winter that featured DC’s warmest December on record.  However, there was a major shift in the weather pattern during the January 2016 when DC’s fourth largest snowstorm on record occurred.  Stay tuned to my colleagues and I on the WUSA9 Weather Team to see what is setting up to be DC’s largest winter storm in several years this week.

Last 1” of Snow (Source: National Weather Service)

Reagan National Airport (DCA): 2.6” (February 20, 2019)
Dulles International Airport, Sterling, Virginia (IAD): 2.0” (January 7, 2020)

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Last 5” of Snow

DCA: 8.3” (January 13, 2019)
IAD: 7.7” (January 13, 2019)

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Last 10” of Snow

DCA: 11.3” (January 23, 2016)
IAD: 22.1” (January 23, 2016)