Christmas in the Nation’s Capital

 

Where's the car ?!

There are two ways you can have a White Christmas: fresh snowfall on Christmas Day or the remains of a previous snowfall.  The National Weather Service defines a “White Christmas” as having “…at least 1 inch of snow being on the ground on December 25.”  Areas farther north and west of the immediate D.C. Metro Area have considerably higher odds of seeing a white Christmas.  

Washingtonians have seen very little December snowfall at all over the last decade.  Nine of the last 10 Decembers in the Nation’s Capital have had below average snowfall.  That led NOAA’s December’s snowfall average to fall from 2.3” for the 30-year period from 1981 – 2010, to 1.7” to reflect 1991 – 2020.

Historically, Washington, D.C. has had measurable snowfall on Christmas Day roughly every 15 years (or nine times since 1884).  The last time was on December 25, 2002 when 0.2” of snow occurred.  Meanwhile, the last time Washingtonians had snow on the ground on Christmas Day was in 2009.  That’s because the Nation’s Capital had its largest December snowfall on record just the week before when 16.4” was measured at National Airport on December 18-19.  Although more than half had melted by Christmas, 7” remained on the ground, creating the last official white Christmas in Washington, D.C.

The average high and low temperatures on December 25 in Washington, D.C. are 47°/33°.  The coldest Christmas Day occurred in 1983 with high/low temperatures of only 14°/3°.  The last time temperatures remained below freezing on Christmas was in 2000 when the high temperature was only 28°.  By comparison, D.C.’s warmest Christmas on record was in 1964 (72°).  More recently, D.C. residents had a high temperature of 69° on December 25, 2015 that tied with 1965 for third warmest Christmas.  Such temperatures are more common in mid-to-late April.

Rainfall is much more common on Christmas Day.  Washingtonians have had measurable precipitation on December 25 a total of 53 times, dating back to 1871.  The most recent rainy Christmas in the Nation’s Capital occurred in 2015.  Last Christmas was a changeable weather day with a high of 57° shortly after midnight and some rain showers.  However, temperatures fell throughout the day with some light snow and flurries Christmas morning.

Winter weather enthusiasts may wonder if a warmer than average December is a reliable indicator of what kind of weather will ensue in January.  The short answer is no.  For example, December 2015 finished as D.C.’s warmest on record but gave way to a colder and snowier than average January.  On the other hand, December 2002 was both colder and snowier than average as part of the epic 2002-2003 winter that finished tied for DC’s seventh snowiest on record.

Washington, D.C.’s Snowiest Christmas Day’s  (Source: NOAA) 

1.  5.4”  (1962)
2.  4.5”  (1909)
3.  4.3”  (1969)
4.  1.0”  (1902)
5.  0.6”  (1935)

 

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“White” Christmas’ in D.C. in Recent Decades  

1.  2009
2.  2002
3.  1993
4.  1989

 

December’s Deadly Tornado Outbreak

 

December 10, 2021 Storm Reports  (Source: NOAA)

Severe weather in December is rare in the United States.  Severe weather refers to a thunderstorm that contains any of the following; wind gusts of at least 58 mph; hail 1”/+ in diameter; or a tornado.  The month of December averages the fewest number of tornadoes of any month with 24 according to NOAA’s National Center for Environmental Information.

A devastating severe weather outbreak occurred on December 10, with dozens of confirmed tornadoes.  The majority of them occurred late in the evening and overnight when a lot of people didn’t get the warnings in time to take appropriate safety precautions.  However, the watches and warnings were in place since it was a well forecast severe weather event by NOAA’s Storm Prediction Center.  Due to the powerful nature of many of the tornadoes, there have been dozens of reported fatalities.  By the time the final number of casualties is known, this could finish as the deadliest December tornado outbreak on record for the United States.

Tornadoes were reported from Arkansas to Ohio, with a few particularly intense EF-3 or stronger tornadoes.  NOAA crews have been busy surveying the damage and rescue teams have been searching for survivors.  Given the scope of the outbreak the final tornado count and intensity of the tornadoes may not be known for some time.  Meanwhile, it’s likely that the destructive tornado that occurred in Mayfield, Kentucky reached EF-5 intensity.

Although not an EF-5 intensity for its entire duration, the Mayfield tornado had a long track across four states and was dubbed the “Quad State Tornado” with a track of more than 200 miles.  Subject to final verification from NOAA, this could break the existing record for longest lasting tornado on record.  Tornadoes are ranked on the Enhanced Fujita Scale, with weak tornadoes being an EF-0 and the highest ranking an EF-5 with winds of greater than 200 mph. 

Several factors contributed to this tornado outbreak.  There was record warmth in the southern Plains states and Tennessee Valley.  Memphis, Tennessee, for example, had a record high of 79° this past Friday.  A powerful area of low pressure also helped create the “lift” in the unstable atmosphere that allowed for the intense, supercell thunderstorms to develop.  A “supercell” thunderstorm is large, long-lasting thunderstorm that rotates.

If the Mayfield tornado is confirmed as an EF-5, it will the first since May 20, 2013 in Moore, Oklahoma.  That would end the longest stretch in U.S. history no F5/EF-5 tornado has occurred.  It would also be the first December EF-5 tornado, and third overall, since December 18, 1957 when one was observed in Sunfield, Illinois.  Accurate tornado records date back to 1953.   Fortunately, as rescue operations continue, NOAA’s Storm Prediction Center doesn’t expect any severe weather in impacted areas during the next few days.

D.C.’s Warm and Dry Start to December

 

The first third of December has been unusually warm in the Nation’s Capital, with five days considerably warmer than average.  There were three days with highs in the 60s at National Airport – D.C.’s official weather reporting site – along with one day in the 70s.  When D.C.’s high temperature reached 70° on December 6, it became the first December day in the Nation’s Capital with highs of at least 70° in six years.

D.C. warmest December on record came in 2015, which had three days with highs in the 70s.  There were also 11 days high temperatures were in the 60s.  Although this month isn’t expected to challenge for D.C.’s warmest, it is well-positioned to finish as a warmer than average December for the tenth time in the last 11 years.  In fact, December has been so warm over the last decade that D.C.’s average monthly temperature (combining daily high/low temperatures) has risen considerably.

December’s average temperature in the Nation’s Capital for the 30-year period of 1981-2010 was 39.7°.  However, since NOAA updated its climate data last winter to reflect the 30-year period of 1991-2020, D.C.’s average December temperature has risen 2.0° to 41.7°.  That’s a huge difference in average monthly temperature over a relatively short period of time.  NOAA’s Climate Prediction Center expects the warmer than average weather to continue for the next one to two weeks.

If high temperatures today reach 70°/+ at National Airport, then that would be the second time this month.  While no 70° December warmth occurred in the Nation’s Capital before this week since 2015, it happened in four consecutive years through 2015.   That was really unusual, though, that one had to go back to 1998 to get four Decembers with 70° warmth in the Nation’s Capital prior to 2011. 

It has also been a dry month, with only 0.01” of rain through December 10.  There has been a near 50/50 split of wetter vs. drier than average Decembers over the last decade, with six that were wetter than average.  NOAA also expects near to slightly above rainfall the rest of the month.  However, given how dry it’s been so far this month, it would take above average rainfall the rest of the month for the Nation’s Capital to merely finish with an average amount. 

Washington, D.C.’s Warmest December’s (Source: NOAA)

1.  51.2° (2015)
2.  45.6° (1984, 1889)
4.  45.5° (2001, 1982, 1971)
7.  45.4° (2012)
8.  45.0° (2011, 1923)
10.  44.5° (1990)