Increasing Temperatures Turn Skyscraper Icicles to Flying Daggers

By Samantha-Rae Tuthill, AccuWeather.com Staff Writer
February 20, 2014; 8:54 AM ET
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After rounds of icy air and piles of snow, many in the Northeast may be excited for a few days of some warmer weather. However, the increase in temperature also brings an array of threats that could be damaging to people or property, such as falling ice, roof collapses and floods.

According to AccuWeather.com Senior Meteorologist Dave Dombek, icicles forming on homes are primarily a result of insufficient insulation and improperly running gutters, though other factors, such as the amount of direct sunshine, can also lead to icicle-forming conditions.

The Plattsmouth Chiropractic Center covered with icicles. (AP Photo/Nati Harnik) (AP Photo/Nati Harnik)

Homes without the right insulation lose heat, which melts the snow off the roof. If the gutters are not clear, the water overflows and freezes when it hits the frigid air. This process can continue for hours, resulting in large, heavy icicles.

An incoming warmup for the Midwest and Northeast, though short lived, will make these existing icicles especially dangerous.

"Thursday into Friday night is going to be the first time in a while that many places will spend the whole time period, both daytime and night, above freezing," Dombek said.

The warmer air will cause faster melting of the icicles, which will loosen them from their points of attachment on roofs and other surfaces. They can come crashing down to the detriment of people and objects below them with the ability to shatter car windshields, as well as cause concussions or even fatalities.

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Recently, falling ice closed streets in New York City as icicles came plummeting to the surface from the top of skyscrapers. One pedestrian was struck with falling ice and required 80 stitches as a result.

Other concerns that the warming weather can bring are increased risks of flooding as snow melts. Many drainage systems are blocked with ice and snow, or debris pushed aside by snow plows. Additionally, ice jams can dam rivers and streams as melting snow rises water levels.

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.

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.

Content contributed by AccuWeather.com Senior Meteorologist Alex Sosnowski

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