2010 February 5-6 Blizzard (Click on images for larger displays)


This storm missed the NWS Albany, NY forecast area, but produced historical amounts of snow in the mid-Atlantic U.S.  The storm was called affectionately “Snowpocalypse” and “Snowmageddon”.  It is worth noting the consistency and accuracy of the successive sets of guidance/ensembles 4 or more days prior to the storm, to just prior to the storm.  Some of the remarkable consistency will be provided below.


850 hPa wind anomalies were pointing to potentially historical snowfall amounts with anomalies exceeding -4 SD.  Also note the very large areal extent to the anomalies exceeding

-3 SD, which gave clues that the precipitation shield extended far beyond the main upper level impulse.




Above:  GEFS 850 hPa winds and anomalies valid 00Z 6 February and 12Z 6 February.




Above:  SREF 850 hPa winds and anomalies valid 00Z 6 February and 12Z 6 February.


250 hPa winds and anomalies were not pointing to a long-duration event, as the upper system was progressive, and 250 hPa U wind anomalies did not approach -2.5 SD.




Above:  NAM and GFS 250 hPa winds and anomalies valid 12Z 6 February.



Precipitation forecasts




Above:  SREF and GEFS probabilities for 2.00” liquid equivalent in 24 hours.



Above:  SREF probabilities for 3.00” liquid equivalent in 36 hours.




Above:  GFS, NAM80 and NAM12 36 hour QPF valid 00Z 7 February.  Note the large area of 2.00-4.00” of liquid equivalent precipitation across the mid-Atlantic.  This is extremely rare for a snowstorm to exhibit such moisture characteristics.




Above:  Water vapor satellite imagery valid 1245Z 5 February, showing the pure tropical moisture being fed into the system, and the unusually large areal extent to the moisture and precipitation.  The large precipitation shield was also evident due to the large area of east winds in the 850 hPa U wind anomalies. The size of the extremely large precipitation shield resulted in very long duration precipitation event, even with the progressive upper level system.  The onset of the precipitation was so far in advance of the upper level energy, that the heavy precipitation occurred for 24-36 hours.  It is important to evaluate more than just the 250 hPa wind anomalies when considering the potential duration of precipitation in a storm.



Above:  Visible satellite imagery valid 1345Z 6 February.  Note the storm had an eye as it tracked offshore the mid-Atlantic U.S.



Above:  Preliminary Nesis Category 3.


Any comments, questions or suggestions, please mail to:Neil.Stuart@noaa.gov