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Posted at 09:55 AM ET, 01/10/2012

The overachieving snowfall of January 9, 2012


Snow total map from the National Weather Service. See also: list of totals.
What was predicted to be a non-accumulating mix of snow, sleet and light rain turned into a surprising mostly snow event Monday, producing a trace to two inches across the region. Officially, National Airport received 0.6”, Dulles 0.5” and BWI airport 0.4”.

Post photographer gallery: Winter’s first snowfall

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The heaviest snow fell south and southwest of the District, with jackpot totals of 1-2” from southwest Fairfax county through central Prince William county and into northern Fauquier county. Some of the eastern suburbs also surpassed an inch, including the southern half of Prince George’s county, and northern Charles and Calvert counties.

Here are some of the more impressive (impressive, being a relative term for this storm) totals:


Oakton, in western Fairfax county, received just over 1” (CWG photographer Kevin Ambrose)
Virginia

Centreville, Va: 1-1.1”
Burke: 1”
Bailey’s Crossroads: 1.2”
Franconia: 1”
Dale City: 1.5”
Gainesville: 1.2”
Manassas: 2”

Maryland

Saint Charles: 1”
Camp Springs: 1”
Forest Heights: 1.5”
Huntington: 1”

Why was the forecast not up to par?

This was kind of a sneaky storm system that just grazed us. We were on the very northern fringe of the precipitation shield, and indeed, locations just 30 miles north of Washington got basically no snow.

Computer models were very erratic in their simulations for this storm. On most model simulations, either no precipitation was shown for the D.C. area or they indicated the atmosphere would be too warm for snow. A few did show just enough cold air and moisture around to produce some snow or mixed precipitation, and we actually had mentioned there was a chance we’d see wet snow flakes or a mix Sunday night into Monday going back to late last week (forecast issued Thursday).

On Sunday, one run of the European model suggested the event might be a little more meaningful than just a few wet flakes but had little support. After looking at Sunday night’s models which hinted snow might be more a concern, we updated our forecast and said a non-accumulating mix of light snow, sleet and rain was becoming increasingly likely Monday. We also put this information out on Twitter and Facebook.


Sledding in Oakton. By CWG photographer Kevin Ambrose.
Of course, the event turned out to be a (little) bit more than a non-accumulating mix. But model simulations didn’t converge on that idea until Monday morning, just as the precipitation was moving in.

This was just one of those “on the edge” forecasts that tipped in the snowy direction. In most cases, they tip the other way. If the system had tracked 30 miles south, we wouldn’t even be having this discussion.

But ultimately, we erred in being a little dismissive of the snowier scenario and not communicating the possibility. So we take responsibility for that...

Here are some more snow photos from Facebook and Twitter followers....

By  |  09:55 AM ET, 01/10/2012

Categories:  Local Climate, Latest, Recaps, Winter Storms

 
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