The Importance of Storm Track

 

Some of DC’s largest snowstorms have occurred during the second half of January, including the infamous “Knickerbocker” Storm of 1922 and, more recently, a record-setting snowstorm in January 2016.  A high degree of skill is required when forecasting snow in the D.C. Metro Area given the complexity of winter storms and the unique geography of the Mid-Atlantic Region.  

Several of the record snow events in the Mid-Atlantic Region over the last 20 years were well-forecast in advance.  For example, the January 22-23, 2016 event tied for fourth largest snowfall in the Nation’s Capital and was first mentioned in forecasts the previous weekend.  Also, area meteorologists, including my colleagues and I on the WUSA9 weather team, gave residents several days advance notice of high impact storms in February 2010 and December 2009.

These storms were such blockbuster events that the computer models meteorologists use were able to identify the seeds that became the storms days in advance.  The farther out from an event you are, there is a higher degree of fluctuation between computer model runs.  That leads to an old adage in the weather community that “the trend is your friend.”  If several models show a particular storm or event over several runs, then meteorologists have more confidence that said event might occur.

The ideal track for a winter storm to bring the D.C. Metro Area appreciable snowfall is just off the Mid-Atlantic Coast.  Whether the storm develops along the U.S. Gulf Coast or off the southeastern coast of the United States – as this weekend’s Nor’Easter did – is irrelevant, so long as the track is close enough to the coast to bring the Nation’s Capital accumulating snow.  However, if the storm develops or tracks to close to the coast, then it could displace the cold air in place. 

There were several notable near misses in the Nation’s Capital when Washingtonians either saw no precipitation or what began as snow changed to rain.  The winter storm on January 16 began as a few inches of snow in the D.C. Metro Area, but changed to rain after sunset as daytime highs reached the low 40s.  That was because the storm track was too far west for the cold air to remain in place.  The area of low pressure essentially tracked up the Chesapeake Bay during the January 16 event, so the changeover to rain occurred.

This weekend’s Nor’Easter developed and tracked just far enough east to prevent the Nation’s Capital from seeing significant snowfall.  Meanwhile, Philadelphia, New York City and Boston will see their largest snowfalls of the winter.  There have been several notable storms over the last 10 – 15 years that have tracked just far enough east where the D.C. Metro Area saw little or no snow, while cities to our north got walloped with snow.  One such example occurred on December 26-27, 2010.  A developing area of low-pressure didn’t intensify rapidly until it was approaching Long Island.  This kept the heavy snow from roughly Atlantic City northward through New York City.  The snow with this storm had a sharp western edge with areas west of the Chesapeake Bay that got no snow.