Dangerous Roof Collapses Possible With Deep Snow, Rain

By By Alex Sosnowski, senior meteorologist.
February 21, 2014, 4:15:05 AM EST

While flooding is likely to be minor and sporadic through Friday, the warmup and rainfall will continue to bring the risk of leaky roofs and roof collapses into the weekend.

This risk is greatest on flat roofs.

"A deep snow varied by drifting, combined with rainfall, natural melting and blocked drainage systems on the roofs can lead to uneven weight distribution," According to Forensic Weather Expert Steve Wistar, "When this weight exceeds the design of the roof, a partial or total collapse could occur."

Property owners may want to consider removing some of the snow from the roof, only if they can do so safely. If any doubt, consult a properly-insured private contractor.

In some cases, strained roofs that survive the added weight from this week's rain could succumb to additional storms later this season.


Cold air is expected to return in stages this weekend, and additional storms with heavy snow are possible beginning next week. The return of cold air will cause slush and runoff to freeze.

The lingering snow cover and added moisture from the rainfall and additional snowstorms will carry the flooding forward through the remainder of the winter and perhaps into the spring.

Frigid Air to Clutch Midwest, Northeast Again Next Week
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Flood Risk Rises With Incoming Rain

As of Tuesday, Feb., 18, 2014, there was as much as 6 inches of water locked up in the snow over parts of the Upper Midwest and northern New England. Farther south in the Midwest and Northeast, there was between 1 and 3 inches of water contained within the snow on the ground.


Over a surface area of one square foot, an inch of water (approximately 10 inches of snow on average) weighs about 5.2 pounds. However, the weight of the snow can vary, depending on its water content when it first fell and how much rain it absorbed later.

Steve Wistar is one of the nation's leading experts on roof snow loads.

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