What Ice Storm Accumulations Mean, How To Prepare And Stay Safe

Jim Cantore Goes Into Heart Of Ice Storm

You may hear meteorologists talk about ice storm accumulations and wonder, "How much ice causes tree damage, power outages? Will travel be impacted and how bad?" These are common questions, so let's break it down for you.

Just a thin coating of ice can result in a travel nightmare, while heavier amounts will severely damage trees and power lines. Strong winds can add extra force to already weighted-down tree branches and power lines, increasing the likelihood of significant damage and long-duration power outages.

Ice Storm Facts

*Ice can increase the weight of tree branches by 30 times.

*A one-half inch ice accumulation on power lines can add 500 pounds of extra weight.

*An ice storm in 2009 from northern Arkansas to the Ohio Valley knocked out power to 1.3 million customers.

*In 1998, an ice storm in northern New York and northern New England damaged millions of trees and caused $1.4 billion in damage. Accumulations were as much as three inches thick.

These ice accumulations are caused by freezing rain.

Freezing rain is a result of snow falling through an above-freezing warm layer in the atmosphere above the ground, which melts the snowflakes into rain. The raindrops then move into a thin layer of below-freezing air near the ground, allowing them to refreeze on contact to roads, trees, cars and other objects.

Sleet, on the other hand, does not accumulate on trees and power lines. However, sleet can accumulate on roads and make travel treacherous. Bottom line is that ice events with more sleet than freezing rain are much less a threat for tree damage or power outages.

What kind of impacts and damage do different amounts of ice cause? 

'Nuisance'

A nuisance ice event is usually one with one-quarter inch or less of ice accumulation.

Even though these lighter accumulations are considered a nuisance, travel can be dangerous even with a light glazing. Bridges and overpasses will become slippery first. Remember if the road, bridge or overpass looks wet, and temperatures are below freezing, it's safe to assume ice is present.

'Disruptive'

A more disruptive ice storm is typically one with ice accumulations from one-quarter to one-half inch.

'Major'

Once ice accumulations exceed one-half inch, the most high-end impacts can occur, including widespread severe tree damage and power outages that may last for days.

The most devastating storms contain ice accumulations of an inch or more.

How To Prepare And Stay Safe

*Avoid driving on icy roads for your safety and the safety of emergency personnel. If you are an emergency responder or must travel in the snow or ice, please keep a winter emergency kit in your car.

*Be sure to charge cell phones and laptops ahead of time. Make sure you have several ways to communicate with others. Consider landline phones, social media, and texting.

*Remember, if it’s too cold for you, it’s too cold for your pets. Plan for pets to come inside, and store adequate food and water for them.

*Children should never play around ice-covered trees; they may be injured if a branch breaks under the weight of the ice and falls on them.

*Think about safe alternate power sources you could use if you lose heat, such as a fireplace, wood/coal stove or portable space heaters. However, be sure to exercise caution.

*Follow manufacturers instructions when using portable space heaters and other devices.

*Never use portable generators, camp stoves and grills inside your home or garage; they should only be used outside. Keep them at least 20 feet away from your home's windows, doors and vents to prevent deadly carbon monoxide poisoning.

*Use flashlights during power outages instead of candles to prevent the risk of fire, and keep plenty of extra batteries on-hand.  

You may see posts circling around social media with crazy freezing rain amounts, but it's important to not take these at face value.

These maps simply show how much precipitation could fall in the form of freezing rain, but not how much ice accumulation actually occurs and in reality, ice doesn't accumulate on power lines and branches as much as these models show.