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December 18, 2009

NWS: 5 to 10 inches, maybe more

As often happens just before Maryland's biggest snowstorms, the National Weather Service's snowfall predictions continued to creep upward on Friday. The first predictions were issued with Thursday's Winter Storm Watch, and they mentioned "more than 5 inches." Feb. 11-12, 2006 Baltimore snowstorm

The Winter Storm Warnings issued overnight for the entire state advise residents to prepare for 5 to 10 inches, with "locally higher amounts possible, mainly in or near Southern Maryland."

The forecast for BWI during the daytime on Saturday now calls for 7 to 11 inches. Add in the 1 to 2 inches expected before dawn Saturday, and you get 8 to 13 inches.

Looking back, it seems to me that is a pattern for the forecasters out at Sterling. They tend to be cautious and conservative with these snow predictions, as they should be, given their responsibilities. As the really big storms close in, and our fate becomes inevitable, they begin to adjust their forecasts, and you can see the numbers begin to climb. Perhaps that's appropriate caution. Perhaps it's driven by sound science.

But it sometimes also seems to leaves them lagging behind some of the commercial and amateur forecasters, who seem to revel in the possibilities on the high side. It's good for ratings. It's good for click counts. It becomes the buzz.

And that's what seems to be playing out this morning. As Sterling weighs each model run, and forecasters add in their own knowledge and experience, their accumulation numbers begin to creep higher. Elsewhere, in the meantime, some broadcasters and commercial forecasters are AccuWeather.comtalking about one to two feet of snow.'s headline this morning (if you can get to it; the site is very slow) warns of "a very disruptive Mid-Atlantic Blizzard." Its snow map (left) shows Baltimore in the 6 to 12-inch band. But blogger Henry Margusity is calling for 12 to 18 inches in Washington (and presumably Baltimore). Some of the computer models last night were even scarier, suggesting an historic dump of 24 to 36 inches.

Baltimore, at least, has never had a 36-inch snowstorm, so I think we can dismiss that as likely fantasy for us. In the mountains, maybe. Southwestern Virginia could see two feet in spots. But not here.

That said, it does look like we are in for a memorable storm. It could well be the biggest since the Feb. 11-12 snowfall in 2006 (photo above) that left 13.1 inches at the airport. If some of the higher predictions prove accurate, it could become the biggest snowfall since the record storm in February 2003, that piled up 28 inches at the airport and paralyzed the region for days.

Even a foot of snow, on top of the inch (officially, at BWI) that fell Dec. 5, and this would become the snowiest December since 1966, when 20.4 inches fell at the airport, still a record for the month. It would also become the fifth-snowiest December since record-keeping began in 1883.

December isn't often a snowy month in Baltimore. The long-term average snowfall in December is just 1.7 inches. Our snowiest months, on average, are January (7 inches) and February (6.4 inches). Here are the "snowiest December" numbers to watch as the snow piles up Saturday on your sidewalk:

December 1966:  20.4 inches

December 1904:  17.1 inches

December 1960:  15.6 inches

December 1932:  14.7 inches

(SUN PHOTO/John Makely/Feb. 12, 2006)

Top 20 Snowstorms in Baltimore: (1891-2006)
128.2 inches ... Feb. 15-18, 20031114.1 inches ... Dec. 11-12, 1960
226.5 inches  ... Jan. 27-29, 19221213.1  inches ... Feb. 11-12, 2006
322.8 inches ... Feb. 11, 19831313.0  inches ... Mar. 5-7, 1962
422.5 inches ... Jan. 7-8, 19961412.3 inches ... Jan. 22, 1987
522.0 inches ... Mar. 29-30, 19421512.1 inches ... Jan. 30-31, 1966
621.4 inches ... Feb. 11-14, 18991612.0 inches ... Feb. 16-18, 1900
720.0 inches ... Feb. 18-19, 19791711.9 inches ... Mar. 13-14, 1993
816.0 inches ... Mar. 15-18, 18921811.7 inches ... Feb. 5-8, 1899
915.5 inches ... Feb. 15, 19581911.5 inches ... Dec. 17-18, 1932
1014.9 inches ... Jan. 25, 20002011.5 inches ... Mar. 21-22, 1964
Posted by Frank Roylance at 10:50 AM | | Comments (2)
Categories: Winter weather


Why did it have to be THIS weekend.....

There's a phenomenal amount of moisture feeding this storm.

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff

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