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Posted at 02:10 PM ET, 02/03/2012

What does 1.7” of snow through January buy Washington D.C. for the whole winter season?


Snow Lovers Support Group: Would you like to join? (Steve Tracton)
Where’s the snow? Washington is of course not a snow town, except maybe in a rare year like 2009-10. Even so, through the end of January we’re running 6.7” below the normal of 8.4” of snowfall by the time February begins. Half a foot of snow below normal -- think of that as a crippling snowstorm which shuts town for a week!

Before this one, just 18 of 124 winters on record (back to 1887-88) witnessed 1.7” or less snow through the end of January. All of this year’s total came in January and it’s been characterized by many as the winter without a winter. But, will that continue?

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Fourteen of the 18 seasons in our current predicament, or worse, finished with a seasonal total of less than 10” of snow. That’s below normal by account of climatology and horrid in the eyes of a snow lover. One additional season finished with less than the current seasonal average of 14.5”, while three finished above to well above average.


Data collected at NWS Baltimore/Washington’s web site.
However, of those 18 seasons with paltry snow amounts like this one, the average amount of total seasonal snowfall that fell during February-April is 81 percent. This compares to an all-time average of 47 percent and a 30-year normal of 42 percent. Snow lovers surely must be hoping more than 42 percent of all the snow we see this season is still to come, or better yet 81!

Since some of the years in that sample had all of their snow after January, in attempt to balance a bit, I also examined seasons in which up to twice as much snow (3.4”) had fallen by the end January. That adds 10 to the sample for a total of 28 winters (3.4” or less). By this measure, the average portion of the seasonal snowfall accumulating in January and beyond is 75 percent.

Examining recent times

In recent history, the early 2000s have been marked by very little snow intermixed with copious snow. The copious snow years are of course easier to remember and much less numerous. 40.4” fell in 2002-03 including 28.8” from February till finish, and then there’s the record breaking 56.1” of snow in 2009-10 that included 32.1” in February alone.

Including those two years, five of the 10 Februaries have featured above average snow. Two of the ten featured above average snow in March. One (2007) even had accumulating April snow!

In the “hurting” category, 2006-07 had even less snow through this point (only 1.3”) than this winter, and it finished with 9.5”. 2008-09 recorded slightly more by now — a whopping 1.9” -- and it finished with 7.5”, including a sizeable 5.5” at the start of March. 2001-02 stood at 2.7” and only picked up another 0.5” for the miserable total of 3.2”. 2007-08 grabbed 1” more from its pre-February total to finish with 4.9”.
30-seasons of “season ending” snowfall amounts beginning in February. The red line is the average of 6.1”.

Possible trends

The 30-year norm for snowfall still to come in D.C. is 6.1”, 4.8” of which falls in February and 1.3” in March. Half of the seasons with 1.7” or less through January finished above that average (and half below). Four of the 18 seasons saw February snowfall greater than the current average of 4.8”, and 11 had March snowfall above the present day 1.3” norm.


A tulip in the snow. By CWG photographer Kevin Ambrose.
That March stat -- 61 percent above normal snow -- might seem particularly interesting, especially if you miss seeing our crystal ball. When broken down by pre-National (DCA) history (mid 1940s) and DCA history, there is a nearly equal distribution, with 6 seasons before and 5 seasons after. Of course, other factors like ENSO state, blocking regimes, and temperatures during the winter are not discussed here but would need to be considered in a deeper examination.

Before the move to DCA, the average through March after a pathetic (1.7” or less) start was 8.3”. After the move, that average is 7”. Removing the high-snow outlier in each group, we get averages of 6” pre and 4.5” post. This, factored in with some evidence that La Ninas (particularly moderate ones) may tend to produce late in the season, could at least keep us watching a few weeks past this month, if warmth ever stays away for longer than a minute.

Baltimore and Dulles


Data collected at NWS Baltimore/Washington’s web site.
Folklore holds, and in this case it is true, that when it comes to low snow totals, National is just about king in the local area. And sure, we don’t all live at the airports. But, the data is plentiful there, and three points are better than one!

Baltimore, whose record is a few seasons longer than D.C.’s, has seen only 11 years with equal to or less snow than this season’s 1.3”. Of those seasons, 84 percent of the winter total was still to come after January. Including snow totals up to double 1.3”, the average seasonal still to come is 76 percent. The 30-year average brings almost exactly half of the winter’s snow from February through April.

Dulles, where historical records are about half as long as D.C. and Baltimore, has seen five seasons with equal to or less than the 2.3” that has fallen through January. In those years, 78 percent of the seasonal total fell from February onward. Factoring in seasons with up to twice as much snow season-to-date brings a normal of 62 percent still to come. Like Baltimore. almost half of the seasonal total usually falls from February through April.

A guess on where we finish?

Now armed with a climatological basis for making an educated guess, it seems that the odds are historically poor to even top 10” on the season in D.C. Reaching average would be fantastic, and getting above might be akin to a mini miracle. It has happened though.

What do you think?

Disclaimer: There is no meaningful correlation between October through January snow and February through April snow when examining the entire set of years regardless of how they started. When examining the smaller subset of seasons, there is some correlation but it is still weak and impacted by outliers on both ends. This post is meant as historical in nature rather than predictive.

By  |  02:10 PM ET, 02/03/2012

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