Winter Finally Arrives!

 

Snowfall Forecast (WUSA9)

Following D.C.’s second warmest December on record, there’s been a hard pivot towards more winter-like weather in the Nation’s Capital.  There has been a net swing more than 30° between yesterday’s high of 63° at 5:06 PM to a 1 p.m. temperature of 29° at National Airport following the passage of a powerful cold front.  Today is D.C.’s most significant winter storm in nearly three years.

January is the coldest month of the year in the Nation’s Capital with an average monthly temperature (combining daily high/low temperatures) of 37.5°.  That’s an increase over the previous average of 35.7°.  Last winter, NOAA updated its temperature and precipitation averages to reflect the 30-year period of 1991-2020.  Since the 2010s were a much warmer decade than the 1980s, it’s not a surprise that January’s average temperature increased by 1.8° when the 2010s replaced the 1980s in NOAA’s previous data set (1981-2010).

D.C.’s coldest time of the year based on average temperatures occur in mid-January.  The daily average high/low temperatures in the Nation’s Capital are 44°/30° for a six-day stretch from January 14 – January 19.  Six of the last 10 January’s have been warmer than average in Washington, D.C.  The warmest January temperature on record is 79° on January 26, 1950.  By comparison, D.C.’s coldest January temperature is -14° from January 1, 1881. 

January has been a relatively dry month in the Nation’s Capital over the last decade.  Eight of the last 10 January’s had below average precipitation.  That includes D.C.’s fourth driest January on record in 2018 (0.94”).  Not surprisingly, NOAA’s January rainfall average for Washington, D.C. dropped from 2.86” to 2.81” in the updated climate data set.  Seven of the last 10 January’s have had below average snowfall in Washington, D.C.  That’s led D.C.’s January snowfall average to fall from 5.6” to 4.9”.  However, January remains D.C.’s second snowiest month of the year narrowly behind February (5.0”).

Despite D.C.’s trend for warmer and drier than average January weather, the right ingredients need to come together only once to create a significant winter storm.  Such is the case today with a significant storm.  NOAA’s Climate Prediction Center expects colder than average weather to continue in the D.C. Metro Area through mid-January.  Near to below average precipitation is expected to coincide with these below average temperatures.

Reagan National Airport (DCA)

Last 1” snowfall: 2.3” (January 31, 2021)

Last 5” snowfall: 8.3” (January 13, 2019)

Last 10” snowfall: 10.3” (January 12 – 14, 2019)