Snowmageddon storm clobbers the Mid-Atlantic with 2 - 3 feet of snow

It's a very white world in the Mid-Atlantic today, where the historic blizzard of 2010 has buried residents under a record-breaking two to three feet of snow. The storm, which President Obama referred to as "Snowmageddon" in a speech before the Democratic National Committee winter meeting, set the all-time record for heaviest snowfall in Delaware history, thanks to the 26.5" that fell in Wilmington (old state record: 25" in the President's Day storm of 2003). "Snowmageddon" dumped the second heaviest at Philadelphia 28.5"), second heaviest at Atlantic City (18.2"), third heaviest at Baltimore (24.8"), and the 4th heaviest at Washington D.C. (17.8"). Several locations in Maryland have seen over three feet of snow, with the northern Washington D.C. suburb of Colesville receiving 40", and the southern Baltimore suburb of Elkridge receiving 38.3". While the blizzard was not an exceptionally strong storm--the central pressure was a rather unimpressive 986 mb at the height of the blizzard, at 9am EST Saturday--it was an exceptionally wet storm. The melted equivalent precipitation for the blizzard exceeded three inches along its core snow belt. That's an phenomenal amount of moisture for a winter storm. The blizzard formed a very unstable region aloft where thunderstorms were able to build, and there were many reports of thundersnow during the height of the storm. These embedded thunderstorms were able to generate very heavy snow bursts of 2 - 3 inches per hour.

A new storm expected to affect the area Tuesday may add to the immense pile of snow on the ground, though the precipitation may partially fall as rain. With only a slow warm up in store for the mid-Atlantic over the next ten days, the snow will stick around for a while. This is a good thing, since a sudden thaw or heavy rain event could generate considerable flooding, if the three inches of precipitation locked in the snow is suddenly released.

Today's blizzard is the second major snowstorm of 16+ inches to affect the Washington D.C./Baltimore region this winter--the other being the 16.4" storm of December 19 - 20. According to the National Climatic Data Center, the expected return period in the Washington D.C./Baltimore region for snowstorms with more than 16 inches of snow is about once every 25 years. Thus, a one-two punch of two major Mid-Atlantic Nor'easters with 16+ inches of snow in one winter is something that should happen only once every 625 years. Such an event has not happened since the beginning of the historical record in 1870. The numbers are even more impressive for Philadelphia, which has had two snowstorms exceeding 23" this winter. According to the National Climatic Data Center, the return period for a 22+ inch snow storm is once every 100 years--and we've had two 100-year snow storms in Philadelphia this winter. That should happen only once every 10,000 years, in today's climate. Of course, the last ice age was just ending around 12,000 years ago, so this probability number has to be viewed with a some skepticism. Still, the two huge snowstorms this winter in the Mid-Atlantic are definitely a very rare event one should see only once every few hundred years.


Figure 1. "Snowmageddon", the Nor'easter of February 5 - 6, just off the Mid-Atlantic coast, at 12:01 pm EST Saturday 2/6/10. Image credit: NASA GOES project.

The top 10 snowstorms on record for Baltimore:

1. 28.2", Feb 15-18, 2003
2. 26.5", Jan 27-29, 1922
3. 24.8", Feb 5-6, 2010
4. 22.8", Feb 11-12, 1983
5. 22.5", Jan 7-8, 1996
6. 22.0", Mar 29-30, 1942
7. 21.4", Feb 11-14, 1899
8. 21.0", Dec 19-20, 2009
9. 20.0", Feb 18-19, 1979
10. 16.0", Mar 15-18, 1892

The top 10 snowstorms on record for Washington, D.C.:

1. 28.0", Jan 27-28, 1922
2. 20.5", Feb 11-13, 1899
3. 18.7", Feb 18-19, 1979
4. 17.8" Feb 5-6, 2010
5. 17.1", Jan 6-8, 1996
6. 16.7", Feb 15-18, 2003
7. 16.6", Feb 11-12, 1983
8. 16.4", Dec 19-20, 2009 (Snowpocalypse)
9. 14.4", Feb 15-16, 1958
10. 14.4", Feb 7, 1936

Top 9 snowstorms for Philadelphia:

1. 30.7", Jan 7-8, 1996
2. 28.5", Feb 5-6, 2010
3. 23.2", Dec 19-20, 2009
4. 21.3", Feb 11-12, 1983
5. 21.0", Dec 25-26, 1909
6. 19.4", Apr 3-4, 1915
7. 18.9", Feb 12-14, 1899
8. 16.7", Jan 22-24, 1935
9. 15.1", Feb 28-Mar 1, 1941

I'll have a new blog on Monday, when I'll discuss if record snow storms are inconsistent with a world experiencing warming. Have a great Super Bowl weekend, everyone!

Jeff Masters