Another Warm and Wet December

This December will finish as a warmer and wetter than average month in the Nation’s Capital for the fifth time in the last six years.  Through December 30, DC’s December average temperature (combining daily high and low temperatures) is 2.1° above average.  Washingtonians also exceeded the December rainfall average (3.05”) with 3.28”.  December 2019 won’t finish as wet as last December (5.82”) or as warm as December 2015 (11.5° warmer than average). 

DC had no measurable snowfall occurred in December 2014, 2015 and 2018.  However, each of the subsequent winters (2014-2015, 2015-2016 and 2018-2019) finished with above average snowfall.  That means there’s good news for snow lovers in the DC Metro Area longing for appreciable snowfall.  It’s true that Washingtonians officially saw 0.4” of snow this month, well below DC’s December average of 2.3”.  However, once the calendar changes to January, there can be a dramatic change in the weather pattern.  For example, a significant dip in the jet stream occurred in early January 2015 that coincided with the passage of a vigorous Alberta Clipper that brought the Nation’s Capital a robust 2.4” on January 6.  What’s more, February 2015 was DC’s coldest February since 1996 and finished with 9.8” of snow. 

December 2015 was DC’s warmest on record and featured more days with highs in the 70s (three) then had lows at or below freezing (two).  It was also a wet month with rain on nine of its final 10 days that helped it finish 1.79” wetter than average.  The first measurable snowfall of the 2015-2016 didn’t occur until January 17 and set a record for DC’s latest first accumulating snowfall.  DC’s fourth largest snowstorm occurred a few days after that. 

December 2018 was another warm and wet month with 5.82” of rain (nearly double DC’s December average of 3.05”) that helped 2018 finish as DC’s wettest year on record.  However, a significant winter storm that spanned three days brought the Nation’s Capital 11.5” of snow the following month – DC’s largest snow event since the record January 2016 storm.

The only colder than average December in recent years occurred in 2017.  However, the 2017-2018 winter finished with half of DC’s seasonal average of 15.4” of snow.  That helps illustrate that a cold December doesn’t always foreshadow a snowy winter, just as a warm and wet December doesn’t portend a warm winter.  Although NOAA’s January outlook is for near average temperatures and above average precipitation in the DC Metro Area, the right ingredients need to come together only once to produce a significant snowfall.

Weather Quiz

When was the last time DC residents had high temperatures in the 60s on New Year’s Eve?

A.  1998

B.  2002

C.  2011

D.  2015

2019: The Year in Weather

As 2019 comes to a close, it’s a good time to reflect upon some of the memorable weather events that DC Area residents have experienced this year.  Check out this story I co-wrote for the WUSA9 website.

December’s First Half

DC’s weather during the first half of December has been remarkably close to average.  Temperatures through December 18 were within 0.6° of the average.  That’s much closer than November, which finished 3.5° colder than average.  And it’s also much cooler than last December which finished 3.8° warmer than average.

The warmest temperature so far this month was 60° on December 10.  The coldest temperature so far this month in DC was 27° on December 18.  What has stood out so far this month has been the relatively high number of rainy and gloomy days.  Ten of the first 18 days of December have produced measurable rainfall in the Nation’s Capital.  While than half of DC’s December days so far have been rainy, Washingtonians have officially had only 2.42” of rain through December 18.  That’s not an unusually high amount.  DC residents had 3.76” of rain for the same period last December.  The Nation’s Capital averages 3.05” for the entire month of December.  

Accumulating snowfall also occurred two days this month with a combined total of 0.4”.  That’s not a significant amount of snow by any stretch, considering DC averages 2.3” for the month.  It is noteworthy, though, since accumulating snowfall has now occurred in the Nation’s Capital in 11 Decembers since 2002.  Today also marks the tenth anniversary of DC’s largest December snowstorm when 16.4” fell on December 18-19, 2009.

Fortunately, for those people tired of the recent stretch of wet weather, there has been a shift in the weather pattern.  NOAA’s Climate Prediction Center expects the next six to 10 days to be drier than average in the Mid-Atlantic Region through December 29.  There is no rain or snow on the WUSA9 7-day weather forecast either, as we expect dry conditions through Christmas Day.

While that’s good news for travelers and last minute holiday errands, it’s not for DC Area residents longing for a White Christmas.  Snow on Christmas in the Nation’s Capital is a relative rarity with only four White Christmas’s in the last 30 years.  Some other cities that see snow on Christmas more frequently than DC include Minneapolis, Chicago, Buffalo, and Albany.

An important distinction is that a “White Christmas” can mean two things.  New snowfall can occur on Christmas Day or snow from a previous storm could linger on the ground on December 25.  The latter tends to occur during very cold Decembers such as in 1989 and 2009.  December 1989 was a very cold and snowy month with 9” of snow in the Nation’s Capital, but the rest of the 1989-1990 winter was mild with below average snowfall (DC averages 15.4” of snow annually).  By comparison, the cold and snowy December 2009 was just a harbinger of what became DC’s snowiest winter on record in 2009-2010.  DC’s last White Christmas was in 2009.