Winter Weather Events

The Nation’s Capital averages 15.4” of snow in a given winter season according to NOAA.  Sometimes it comes in a series of smaller storms as it did during the 2014-2015 winter; in other winters it occurs primarily during one large storm such as during the 2015-2016 winter.  NOAA has already released its winter weather outlook, while my colleagues and I on the WUSA9 weather team will release ours soon. 

There are a lot of factors to consider such as the status of the El Nino Southern Oscillation, “ENSO,” that refers to the presence of El Nino, La Nina or neither during a neutral phase.  It’s also important to consider the status or “phase” of the North Atlantic Oscillation (“NAO”).  Over the last 30 years, there have been a number of memorable winter seasons that could offer some clues as to what might be in store for the 2019-2020 season in the DC Metro Area.  Five of the last 10 winters have been snowier than average in Washington, D.C., including last winter.

Sometimes winter arrives early as it did during the 1989-1990 season.  November 1989 was 1.6° cooler than average in the Nation’s Capital and saw 3.5” of snow (seven times the monthly average).  Meanwhile, December 1989 was an astounding 11.8° colder than average in the Nation’s Capital, making it DC’s coldest December since 1917.  A total of 12.5” of snow occurred during those two months.  However, the weather pattern changed dramatically to being significantly warmer than average when January arrived.  A combined total of only 2.6” of snow fell from January 1 through March 31, 1990.  This was an ENSO neutral winter.

On the opposite end of the spectrum was the 2015-2016 winter season.  December 2015 was DC’s warmest on record.  The first measurable snowfall of the winter didn’t occur until 0.3” fell on January 17, 2016.  That set a new record for latest first measurable snowfall of the season.  Less than a week later, DC residents experienced one of the largest snowstorms on record when a total of 17.8” of snow occurred on January 22-23.  The rest of the 2015-2016 winter season was unremarkable and DC had a seasonal snow total of 22.2”.  A particularly strong El Nino occurred that winter and was a contributing factor in the 2015-2016 winter weather events.

By comparison, the 2014-2015 winter season had a weak episode of El Nino and DC saw a series of smaller snowstorms.  At least 0.1” of snow fell on 14 days between January 1 and March 31, with a seasonal snow total of 18.3”.  Unlike the 2015-2016 winter when over 80% of the snow occurred during the record January 2016 storm, the largest daily snowfall of the 2014-2015 winter season was 4.8” on March 5, 2015.  Another interesting fact is that March has been DC’s snowiest month of the year in four of the last 10 years.  One of those winters was the weak La Nina season of 2017-2018, when February was 1.7° warmer than March’s monthly average temperature (combining daily high and low temperatures).  That’s exceptionally rare since spring not only arrives in March but December, January and February also average more snowfall in the Nation’s Capital. 

NOAA’s winter weather outlook calls for warmer and wetter than average conditions in the Mid-Atlantic Region.  However, snow-lovers shouldn’t fret since the right ingredients only have to come together once to produce a large snowfall.  That’s what happened during the 2015-2016 winter season which got off to a record warm start in December and didn’t see any measureable snowfall until mid-January.