Ice storm potential remains high in Missouri

Every winter brings freezing temperatures, which when accompanied by moisture, can cause dangerous conditions on the roads.

Snow is not the only precipitation threat during the winter months. Ice storms, caused by freezing rain, can cripple entire cities and they are not unusual for Missouri winters.

In fact, Missouri has some of the highest average number of days with freezing rain per year and the average number of continuous hours with freezing rain in the country.

The most recent freezing rain event in central Missouri happened January 2007. On the 12th and 13th, less than a half-inch of ice fell in parts of Mid-Missouri.

The ice knocked out power to more than 300,000 people across the state, killed one person and led the governor to declare a state of emergency. Damage from the storm ended up costing about $350 million.

Ice storms occur when snow or ice particles fall through a layer of air that is above freezing. That causes the ice to turn to liquid rain. When the rain passes through a shallow layer of cold, below freezing air near the surface, it becomes super-cooled.

As it hits the ground, it freezes on contact and creates a glaze of ice.

A tiny bit of ice can create huge problems. Just hundredths of an inch of ice causes slick roads, leading to car accidents. And less than half an inch of ice on power lines can add nearly 500 pounds of extra weight per line. That same amount makes tree branches 30 times heavier.

The effects of ice storms also last much longer than snow storms. Roads are nearly impassible and downed trees and power lines are more likely.

Mid-Missouri has been spared major ice storms for nearly six years, but what about this year?

For a major ice storm to form, cold Canadian air flows in around an area of high pressure to the north. To the south, a storm system will feed warm air and moisture northward. The warm air will rise above the cold air, creating clouds, rain and freezing rain at the surface.

As we’ve already seen this fall, the battle between warm and arctic air masses will likely continue as we head into winter.

As long as Missouri remains between the battling air masses and we get a southern-moving winter storm, our chances of seeing a potential ice storm will remain high.

It’s difficult to forecast ice amounts, but just a minor amount can lead to trouble.