D.C.’s Hard Pivot to Winter

 

D.C.’s unusually warm start to November has quickly become a distant memory following a particularly cold week.  Yesterday’s high of 41° made for the coldest day in the Nation’s Capital since March 28 (40°).  Following another cold day today, temperatures will start to moderate and reach the 50s by tomorrow.  Highs for much of the upcoming Thanksgiving holiday weekend will be near average in the mid-50s for the Nation’s Capital.  That will feel balmy compared to the January-like chill that’s enveloped so much of the eastern United States over the last week.

These large fluctuations in temperature can be attributed to a shift in the position of the jet stream.  According to the National Weather Service, jet streams are “…relatively narrow bands of strong wind in the upper levels of the atmosphere. The winds blow from west to east in jet streams, but the flow often shifts to the north and south. Jet streams follow the boundaries between hot and cold air.”  The major shift from warmer than average weather when the jet stream was well north of the D.C. Metro Area changed to cooler than average when a “dip” in the jet stream occurred that allowed the colder than average weather to move south.

It’s been so cold in the Nation’s Capital that D.C.’s average monthly November temperature (combining daily high/low temperatures) went from being 10.8° above average for November 1 – 12, to being 3.4° above average as of November 20.  A drop in monthly average temperature this great over the course of a week is dramatic and underscores how unusually warm the first 12 days of November were in Washington, D.C.

Given that NOAA’s temperature outlook is for near average temperatures in the D.C. Metro Area for the rest of the month, November 2022 should finish as a warmer than average month.  Some may wonder whether November weather trends can foreshadow what the upcoming winter season will be like.  There have been some winters when November’s weather in the Nation’s Capital did, in fact, do that.  Such was the case during the 1995-1996 winter season.  November 1995 was 6.5° colder than average in Washington, D.C. with 0.5” of snow.  As longtime Washingtonians may recall, 1995-1996 was D.C.’s third snowiest winter on record with 46” – roughly triple the seasonal average of 15.4” at the time.  That winter was also 2.9° colder than average and featured a moderate episode of La Nina.

On the other hand, November 2009 was 2.6° warmer than average in Washington, D.C. and gave way to what became D.C.’s snowiest winter on record.  A total of 56.1” of snow fell in the Nation’s Capital during the 2009-2010 winter.  The 2009 - 2010 winter was also 2.4° colder than average.  However, unlike the 1995-1996 La Nina winter, it featured one of the strongest El Nino’s on record.  Thus, while November’s weather can sometimes foreshadow what the upcoming winter season will be like, there are too many variables to rely solely on November weather as a predictor.