Washington, D.C.’s Missing Snow

 

Snowfall has been such a rare commodity in recent years that NOAA’s annual snowfall average for Washington, D.C. decreased when the climate records were recently updated.  This past winter NOAA updated its climate records to reflect the 30-year period of 1991-2020, replacing the previous data set from 1981-2010.  Since four of the last five winters had below average snowfall, D.C.’s annual snowfall average decreased from 15.4” to 13.7” in NOAA’s updated weather averages.

Last winter, for example, had below average snowfall with a seasonal total of only 5.4”.  January 2019 was the last time D.C. residents had a daily snowfall of more than 5”.  2018-2019 was the only winter in the last five years D.C. finished with above average snowfall.

D.C. residents haven’t had much snow in December either over the last decade.  December used to be D.C.’s third snowiest month of the year, but has since been replaced by March.  March has been the only month in the last decade that Washingtonians often had above average snowfall, with five such occurrence since 2011.  Consequently, D.C.’s March snowfall average increased from 1.3” to 2.0”.  Meanwhile, Washingtonians haven’t had so much as an inch of December snowfall since 2017.

Winters tend to be cyclical in the DC Metro Area, with several snowier than average seasons 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 D.C. Area winter weather enthusiasts with only scant amounts of snowfall.

A lot of attention is given to seasonal weather forecasts that discuss whether temperatures and precipitation will be above or below average.  A key factor meteorologists look at when issuing winter weather outlooks is the ENSO status that refers to the presence of El Nino, La Nina or neither. 

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 included D.C.’s warmest December on record.  However, there was a major shift in the weather pattern in January 2016 when DC’s fourth largest snowstorm on record occurred.  Stay tuned to my colleagues and I on the WUSA9 Weather Team for changes in the evolving forecast on winter weather for this season.

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

Reagan National Airport (DCA): 2.3” (January 31, 2021)
Dulles International Airport, Sterling, Virginia (IAD): 1.0” (February 18, 2021)

Last 5” of Snow

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

Last 10” of Snow

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

 

Following a Cold November, December Gets Underway

 

November 2021 was a colder and drier than average month in the Nation’s Capital.  Washingtonians finished with only a third of November’s rainfall average or 0.98”.  That made for D.C.’s third November over the last decade with less than an inch of rain.  To add to that, temperatures were below average on 20 out of 30 days last month as November finished 2° cooler than average.  It was the fourth time in the last five years November was colder than average in Washington, D.C.

Meteorological winter officially got underway on December 1 and continues through the end of February.  Average daily temperatures fall throughout December, according to NOAA.  D.C.’s average high/low temperatures range from 53°/38° on December 1 to 44°/30° on December 31.  D.C.’s warmest December temperature on record is 79° (December 7, 1998), while its coldest December temperature is -13° (December 31, 1880).  Eight of the last 10 Decembers have been warmer than average in Washington, D.C.  D.C.’s warmest December on record occurred relatively recently in 2015.

The Nation’s Capital averages 3.41” of rain in December.  While nine of the last 20 December’s have been wetter than average, seven of the last 20 have been snowier than average.  Washingtonians can expect an average of 1.7” of December snowfall (2.8” at Dulles Airport).  However, nine of the last 10 Decembers have had below average snowfall, with 2017 being the lone exception.  D.C.’s wettest December (7.56”) occurred in 1901 and driest (0.19”) in 1889.  By comparison, D.C.’s snowiest December occurred in 2009 with 16.6” (due to one of D.C.’s largest winter storms on record). 

These statistics help illustrate that December’s weather can have wide fluctuations from one year to the next.  The right ingredients need to come together merely once to produce a large winter storm.  However, in this La Nina winter, NOAA’s winter outlook is for warmer than average temperatures with near average precipitation.  Many of D.C.’s snowiest winters have occurred during El Nino winters with 1995-1996 being the notable exception.

Although there are several rainfall chances next week, no significant rainfall or wintry precipitation is expected.  That’s not to say the weather during the second half of the month won’t shift, but NOAA predicts above average temperatures will continue during the next one to two weeks for much of the eastern United States.

 

Meteorological Fall Comes to a Close

 

Meteorologists have a different benchmark for measuring seasons than the standard astronomical calendar most people are familiar with.  For the sake of climate records, meteorologists break up the four seasons into equal, three-month segments.  For example, “meteorological fall” began on September 1 and comes to a close today, November 30.  Meteorological winter officially gets underway tomorrow and continues through the end of February.  Since the fall comes to its unofficial conclusion today, we can reflect upon the D.C. Area weather headlines of the last three months.

November 2021 has been a cooler and drier than average month.  That couldn’t be more different than last November, which finished as one of D.C.’s warmest and wettest on record.  Temperatures this month have been streaky with several consecutive warmer than average days alternating with cooler than average days.  However, this month will finish with 20 out of 30 days that were colder than average.  It’s also been a dry month with measurable rainfall on only seven of the last 30 days.  D.C.’s November rainfall total will be 0.98”.  That’s the third November during the last decade with less than an inch of rain. 

By comparison, October 2021 was a very warm month in the D.C. Metro Area.  It finished as the second warmest, behind only 2007.  Meanwhile at Dulles Airport, October 2021 tied 2007 for warmest on record.  Rainfall was also very streaky last month.  Although only 0.42” accumulated at National Airport through October 24, two significant rainfall events during the final week of October produced a two-day rainfall total of 2.70”.  That helped October 2021 finish close to average instead of finishing among the driest on record.  D.C.’s most impressive weather statistic during all of October is that 28 of the 31 days last month were warmer than average.

D.C.’s trend of streaky 2021 fall weather began in September when accumulating rainfall was spotty.  The majority of September’s rainfall total occurred on only two days.  The remnants of Hurricane Ida brought the Mid-Atlantic Region heavy rain and severe weather on September 1 with 1.34” at National Airport.  Another 1.30” fell on September 23.  September’s average monthly temperature (combining daily high/low temperatures) finished nearly 1° above average.  It was also slightly wetter than average (0.10”). 

This fall will finish a warmer than average season overall, but with below average rainfall.  Seven of the last nine autumns have had below average rainfall in Washington, D.C.  That follows a stretch of four consecutive autumns (2009-2012) when Washingtonians had above average rainfall.  NOAA’s outlook for the upcoming winter season weighs heavily on the current episode of La Nina and expects the Mid-Atlantic Region to have warmer than average temperatures with near average precipitation.  Four of the last five winters have had below average snowfall in the Nation’s Capital.