Weather Watch

By Dave Nicosia

Ice storms: winter’s menace

When one thinks of winter, snow is often the first thing that comes to mind. But, winter weather can also include sleet, freezing rain and just plain rain. When the temperature is below freezing and rain falls, the raindrops freeze on contact, forming a glaze of ice. If the ice builds up, it can weight down objects like trees and power lines. In extreme instances, the ice can build up enough to cause trees and power lines to fall. In addition, freezing rain can turn roads into an ice skating rink. Sleet occurs when raindrops freeze before hitting the ground. Sleet accumulates much more slowly than snow and does not form a glaze of ice on objects. It makes roads slippery, but does not have the impact that freezing rain does.

Often, sleet and freezing rain occur together in a winter storm.

One of the worst ice storms on record occurred in southeast Canada, northern New York and northern New England in January, 1998. Ice accumulated between two and five inches on trees and power lines, causing massive damage. Damage estimates were about 5.4 billion dollars from this ice storm. In northern New York, as many as 80,000 people were without electricity, and an estimated 16,000 trees were downed by heavy ice. Some people were without power for weeks. More than 5,000 people lost telephone service. Over 1000 people took refuge in public shelters. Sadly, this ice storm claimed 28 lives.

Freezing rain occurs when a layer of warmer, above-freezing air occurs above a colder, sub-freezing layer of air. Rain occurs in this layer, which falls into the colder air at the surface of the earth, eventually making contact with sub-freezing objects on the ground to form a coating or glazing of ice. When the sub-freezing layer of air at the surface of the earth is thick enough, the rain will have time to freeze and form a frozen raindrop. This is how sleet forms. When this sub-freezing layer of air near the ground is thinner, the rain won’t have time to re-freeze. This is freezing rain.

Central New York and northeast Pennsylvania have one of the highest incidences of freezing rain in the U.S. On average, our region has 12 days per year when freezing rain occurs. A severe ice storm occurred in New York, Pennsylvania and New Jersey in January of 1953. Ice accumulated up to four inches on trees and power lines. 50,000 people lost power. The ice storm caused millions of dollars worth of damage to our region.

How can you prepare for the next ice storm? Having an alternate source of heat is very important, because one of the first “casualties” of ice is power. In addition, you should avoid travel if an ice storm is predicted. Remember, it does not take very much ice on roadways to create treacherous road conditions.

The National Weather Service issues winter storm “watches” anytime a major ice storm is a possibility. “Warnings” are issued when damaging ice accumulations are imminent or occurring. Winter storm warnings usually are issued when half an inch or more of ice accumulation is expected. Winter weather “advisories” are issued for any accumulation of ice on roads. An advisory implies that conditions won’t be dangerous if proper precautions are taken. Often, the best precaution is not to travel.

For more information, visit the Binghamton National Weather Service web site at www.nws.noaa.gov/er/bgm, or www.nww.noaa.gov/om/winter/index.shtml. You can also send me e-mail with your questions at david.nicosia@noaa.gov.