AccuWeather.com

By Alex Sosnowski, Expert Senior Meteorologist

Jan 12, 2011; 11:07 AM ET

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Most people are aware of the dangers presented by an icestorm coating roads, sidewalks, trees and power lines. However, serious problems with ice formation often follow storms that never brought ice in the first place.

The partial melting and subsequent freezing episodes that follow snowstorms can contribute to serious injury.

The two types of ice formation we speak of are black ice and icicles.

The ice in this photo can be easily seen. However, there are not so obvious dangers following winter storms. Photo by AccuWeather.com Facebook fan Irena taken Tuesday, Jan. 11, 2011.

Black Ice

A contracted plower comes by and pushes aside the snow from a parking lot then applies ice melting compounds such as rock salt before leaving.

While the situation may indeed be safe in the short-term, episodes of natural melting of the piles of snow over the hours and days tend to dilute the treatment with time.

The stage is then set for a slip-and-fall incident on black ice during the evening hours or the following morning. In this situation, areas made wet by natural melting froze into a thin sheet of transparent ice.

According to Dr. Joe Sobel, head of AccuWeather.com Forensics, "This is the most common incident following winter storms."

"Over the past four decades, AccuWeather.com Forensics has prepared over a thousand address-specific studies, reconstructing the weather for slip-and-fall incidents," Sobel said.

"Ice can form on cold surfaces, when the air temperature is above freezing," Sobel added.

Icicles

Another, less common, but dangerous situation is falling icicles in the days following a snowstorm in urban areas.

The most common area for icicles to form is at the edge of roofs or on the metal canopies of older bridges.

Conditions are right for icicle formation when the air temperature is below freezing and the roof or bridge canopy surface temperature is above freezing.

Heat escaping through the building or from the warming direct rays of the sun can cause part of the snow to melt. As this water drips into below-freezing air, the icicle forms.

The icicles then fall when their own weight becomes too much or when the air temperature inches above the freezing mark, striking unsuspecting pedestrians or motorists passing by underneath.

Property owners and government officials are urged to post warning signs when dangerous conditions from icicles or black ice exist or to correct the problem.

A heating cable can be used to prevent icicles from forming on the eaves of roofs.

Be sure to apply a fresh dose of ice-melting compounds on wet areas during the late afternoon hours "before" black ice forms on sidewalks and parking lots.