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Yesterday I posted several times that the big blizzard of this weekend was confirmed as the all-time greatest snowfall ever recorded in Baltimore.  (Of course, there must have been bigger storms many years ago.)

But today, on TV and Internet, I've seen several reports that claim it was only the third all-time (and the December 19th event ranks 8th).

How could this be?  What explains the discrepancy?  This puzzled me so I poked around and found the answer.

In addition to hearing several weather broadcasters specifically saying that it was the all-time greatest in Baltimore, my confidence about that was based on local meteorologists saying repeatedly that the latest total they had from the official station at BWI airport was from 11 a.m.--and it continued snowing very hard for another four hours after that.

But as it turns out, a contractor made a fundamental error in the snow measuring at BWI, and we may never have a proper official number:

The contractor paid to make snow measurements at BWI for the weather service (the NWS has none of its own personnel there) evidently failed to follow NWS protocols in measuring the snow.

Those rules say the observer must allow snow to fall on an official "snow board" for six hours, then wipe it clear and repeat the procedure every six hours until the snow ends.

The technique is designed to split the difference between measuring all the snow at once (which means the snow will have compacted some from its own the weight), or measuring it more frequently, and perhaps exaggerating the snow depth by eliminating most compaction.

The contractor measured every hour on the hour and added it up. That produced a total of 28.6 inches. He also took a "snow depth" reading, meaning that he measured all the snow at once, after it stopped falling. Because of compaction, that came to 24.7 inches.

"We don't have an observation for every six hours," Lee said.

Sterling is now consulting with headquarters, and with climatologists, to figure out how to make a reasonable estimate of what a six-hour measurement might have been. "We'll have to come up with an official estimate somewhere between the 24.7 inch snow depth and 28.6," Lee said.

Source: (the Baltimore Sun)

This is not terribly important, but I thought it was interesting.

I'm estimating the total at my property in Carroll County, MD (30 miles NW of Balmer) at 31 inches or more, because just as the snow was ending I measured one open (non drifted) spot at 27 inches--and I'm sure there was at least 4 inches of compaction from this extremely dense snow, probably more.

I think the highest official total was 40 inches at Colesville in Montgomery County, MD, quite close to DC.  Much of DC got quite a bit more than the "official" total of 17 inches at National Airport.

We're only halfway through the winter, and this is already the all-time snowiest winter in Maryland history. Another winter storm watch already went up for another storm to hit Balmer and DC on Tuesday. Some weather guys are saying more than a foot; others 3 to 6 inches.

This week I need to invest in some better snow removal stuff, like a Wovel ( and a snow-blower. The last two days have almost killed us from shoveling and plowing and towing.  I'm so sore I can hardly walk.  But we did finally dig out way out and were able to go out to the storm, and survived the drive up the big hill near our place that is still covered with six inches of ice.

Many people are not so lucky. More than 100,000 are still without power in the DC area, and many side streets, especially in the burbs, are still unplowed. The federal government is closed tomorrow. Maryland Governor O'Malley suggested that everybody stay home until Wednesday.

Originally posted to Timaeus on Sun Feb 07, 2010 at 03:23 PM PST.


For those clobbered by this storm:

35%12 votes
41%14 votes
14%5 votes
8%3 votes

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