Here five things you need to know about ice storms and how to prepare.
1. What Causes an Ice Storm
Ice forms when freezing rain accumulates on surfaces and the ground. Freezing occurs when air warmer than the freezing mark above the ground moves over subfreezing air near the ground. When snow aloft falls through the warmer layer it melts into rain. Then, as the rain droplets fall into the shallow layer of subfreezing air, the droplets freeze upon contact. This creates a glaze of ice.
Temperatures both at the surface and a few thousand feet above the ground helps determine the type of precipitation that is observed.
In most areas of the U.S., an ice storm typically refers to events where a quarter-inch of ice accumulation occurs producing a significant and possibly damaging accretion of ice.
If less than a quarter-inch of ice is produced, it's usually more of a nuisance event with less severe impacts. However, it's important to remember that even a light glaze of ice can make travel hazardous.
2. Significant Impacts Are Possible
When a quarter-inch or more of ice builds up, severe impacts can result. Ice can increase the weight of tree branches up to 30 times and can add 500 pounds of extra weight to power lines. Consequently, tree branches, power lines and power poles can fall.
This damage to trees and power lines can begin when ice accumulates between a quarter- and half-inch. Roads also become slippery at this stage.
When more than half-inch of accumulation occurs, widespread damage to trees and power lines can be expected and roads become impassable.
If strong, gusty winds accompany freezing rain, the chance for damage increases due to the added stress on trees and power lines. Downed trees can block roads, making driving even more dangerous.
3. Ice Storms and Their Impacts Can Last for Days
Depending on the severity of the ice storm and the weather pattern, impacts can persist for days. If more than a half-inch of ice occurs and damage is widespread, it can take quite a while to remove trees and repair power lines.
This can result in a loss of electricity and heat for several days. In some cases, hypothermia can become a concern due to the prolonged cold conditions and lack of heat.
An example of how an ice storm develops.
The other factor to consider is how cold it will be after the storm. If temperatures do not rise above the freezing mark, then not much melting will take place, especially in areas where there isn't much sun.
This is especially important in areas such as the South, where there is limited equipment and supplies to treat roadways.
One other consideration is if melting does occur and then the temperature drops below freezing, black ice can form, resulting in addition slippery travel conditions.
4. You Need to Prepare Ahead of Time
To mitigate the potential impacts that can occur from an ice storm, it's necessary to prepare ahead of time.
If you're stuck at home for several days make sure you have enough non-perishable food and any supplies you may need including water, a cooler with ice and prescriptions. If you have canned foods, be sure to have a non-electric can opener.
If you lose power it is a good idea to have flashlights, batteries and candles on hand. Remember to keep the doors to the refrigerator and freezer closed to help keep the food cold.
Charge any necessary electronics, such as your cell phone. If possible, have a secondary source of heat. You should also have a first-aid kit, some cash and have your vehicle filled with gas, according to FEMA.
Consider pruning limbs or removing trees leaning toward your home before the ice storm to avoid the potential of falling trees or limbs on your home.
5. They've Happened Many Times Before
One of the most devastating ice storms happened in portions of northern New England, upstate New York and southeastern Canada January 5-9, 1998. Ice accumulated up to 3 inches in some areas resulting in extensive power outages that lasted for days and in some cases weeks. Damaged totaled $1.4 billion in the U.S., $3 billion in Canada. Sixteen deaths were reported in the U.S. and 28 deaths in Canada.
Many ice storms take place in the South, including one in February 1994, which impacted areas from Texas and Oklahoma eastward to the Carolinas. More than 2 million lost power. Some residents in Mississippi were without power a month after the storm. At least nine deaths were attributed to the storm.
More recently, Winter Storm Goliath brought ice from areas in the southern Plains into the Midwest in late December 2015. Up to 1 inch of ice was reported near Yukon, Oklahoma, and 1/4 inch of ice downed numerous power lines and trees in Monmouth, Illinois.
A month before Goliath, Winter Storm Cara brought icy conditions to the southern Plains. Winds, freezing rain and sleet affected power lines northwest of Oklahoma City, leaving more than 100,000 customers without power, many for up to a week.
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