Watts Up With That?
Tuesday, Dec 22nd, 2009

UPDATE: The East coast snowstorm seen from space


Image: NASA Earth Observatory – click for hi-res version*
The Mid-Atlantic states were completely white on Sunday, December 20, 2009, in the wake of a record-breaking snow storm. The storm deposited between 12 and 30 inches of snow in Virginia, Maryland, and Washington, D.C. on December 19, according to the National Weather Service. For many locations, the snowfall totals broke records for the most snow to fall in a single December day.

The storm shut down the federal government in Washington DC, stranded travelers, left hundreds of thousands without power and sharply cut holiday sales the weekend before Christmas.

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From the “weather is not climate” department here’s interesting news from the National Operational Hyrdologic Remote Sensing Center. While certainly not unprecedented or unusual, it is interesting, especially when comparing years past and the snow coverage using the website date selector. Here’s today’s snow depth map:



Indeed, it looks like a white Christmas for much of the USA. Here’s the data:

December 21, 2009

Area Covered By Snow:51.7%Area Covered Last Month:8.0%Snow DepthAverage:3.8 inMinimum:0.0 inMaximum:887.0 inStd. Dev.:6.4 inSnow Water EquivalentAverage:0.7 inMinimum:0.0 inMaximum:435.0 inStd. Dev.:1.4 in

Their weather summary indicates more snow on the way:

One to 3 feet of snow fell in the western Plains yesterday, while up to 1/2 inch of freezing rain fell in the central Plains. The precipitation was in response to a potent upper low in the Southern Plains and an associated surface low, which caused upslope flow conditions. The heaviest snowfall amounts were observed in the Colorado Front Range and in the Sangre de Cristo mountains of New Mexico. Strong surface winds in these areas caused much blowing and drifting snow.

Most of the snowpack across the West and western Plains is cool, with cold conditions at the lower elevations of the Great Basin. In the central Plains, where rain and snow fell yesterday, the snowpack there is warm, but snowmelt occurred along the southeastern edge of the central U.S. snowpack. Very warm conditions exist on the windward side of the Cascades where warm onshore flow occurred yesterday; slow snowmelt occurred there. Strong surface winds caused high blowing snow sublimation in the Western Plains from southeastern Wyoming and the Nebraska panhandle southward to northeastern New Mexico.

The upper low, currently over the Central Plains, will move slowly northeastward during the next three days, passing through the Great Lakes region by Sunday. A surface low will accompany the system. Little additional deepening of the system is expected since it appears that dry air is wrapping around the system. But on the cold side of the low, about 1/2 foot of snowfall is expected today in northeastern Colorado through southwestern Minnesota today. Heavier amounts are expected in orographically-favored areas of the Western Plains and northern Front Range. Snowfall is expected in the eastern part of the Upper Midwest and south of western Lake Superior. Up to 1/2 foot of snowfall is possible in this band with higher amounts snowfall likely in northwestern Wisconsin and the Michigan Upper Peninsula.

A deep surface low just off the central British Columbia coast has a cold front extending southward through the Northwest. Onshore flow behind the cold front and midlevel dynamics associated with the front will bring up to a foot of snowfall to the Cascades, Intermountains, Northern Rockies, and northern Sierra Nevada today and from northwestern Wyoming through southern Utah tomorrow. Another front will bring 4 to 8 inches of snow to the Cascades on Saturday.



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