At least two feet of snow had fallen in parts of New York by Monday evening and the weather system responsible is expected to bring similar conditions to Indiana, Michigan and Ohio later today.
The National Weather Service said 24 inches of snow had fallen at Constableville, at the east end of Lake Ontario on the Tug Hill Plateau, by late Monday. In western New York, moisture from Lake Erie had turned into 23 inches of snow by midmorning at Ellicottville, south of Buffalo. In northwest Pennsylvania, Erie reported as much as 14 inches of snow Monday morning.
It wasn't the first snowstorm this season in the Northeast. In late October, a storm spread just over a foot of snow over parts of northern New Jersey, northeast Pennsylvania's Pocono Mountains and New York's Catskill Mountains, and heavy snow also fell at higher elevations of northern New England.
A heavy snowfall brings with it the danger of roof collapses, which was the case in parts of New England and Wisconsin last winter. The Institute for Business & Home Safety has found that the age of the building is a major factor in the snow load risk, although snow load designs have not changed much in recent years. Light metal buildings will typically have less capacity to handle a high snow load. For flat roofs, the step-down area between roof sections is a potential source of roof overload because of the tendency for ice and snow collection.
The best source for determining how much snow load a building can handle is the design plan. IBHS says most roof designs can handle at least 20 lbs per square foot. These designs can range from 10 to 20 lbs per square foot in Mid-Atlantic states, and between 40 and 70 lbs per square foot in New England. IBHS offers these general guidelines to help estimate the weight of snow:
Fresh snow: 10-12 inches of new snow is equal to one inch of water, or about 5 lbs per square foot of roof space, so you could have 4 feet of new snow before you need to worry.
Packed snow: 3-5 inches of old snow is equal to one inch of water, or about 5 lbs per square foot of roof space, so anything more than 2 feet of old snow could be dangerous.
The total accumulated weight of two feet of old snow and two feet of new snow could be as high as 60 lbs per square foot of roof space, which is getting toward the limits of even the best designed roof.
If there's ice, it's much heavier, with one inch equaling about a foot of fresh snow.
For safe removal that won't endanger you or damage your roof, consult a roofing contractor.
To help minimize the risks from melting snow, IBHS suggests keeping attics well ventilated to reduce the risk of ice dams forming. A warm attic melts snow on the roof, causing water to run down and refreeze at the roof's edge where it's cooler. An ice buildup blocks water from draining and forces water under the roof covering and into the attic or down the inside walls.
Commercial buildings with flat roofs are particularly vulnerable to water leaks if ice dams clog roof drains. Water can also find its way inside on sloped roofs along the eaves.
To maintain proper drainage, remove snow from window wells and all walls. Clear debris from basement drains. Make sure gutters are clean and stable to ensure proper drainage.
IBHS research shows about $1 of every $5 paid for home and business property losses in recent years has stemmed from damage due to freezing weather, snow and water leaks. For more information visit the Freezing Weather section of this site.