Freezing rain risks vary
This winter's storms, combined with see-saw temperatures, have been nothing new for the central United States. But, even long-time Plains dwellers were a bit nervous some weeks ago when forecasters called for a gigantic front to deposit freezing rain--and then snow.
"Freezing rain is always interesting. You're on a skating rink everywhere you go. Unfortunately, the weather pattern can also cause tremendous amounts of tension, disruption and damage. Just ask Kansas Citians about the ice storm of 2002. Or, Wichita residents about 2005. They were at the epicenter of ice storms that permanently changed their regions' landscape of trees," said Mary Knapp, State of Kansas climatologist, based with Kansas State University Research and Extension.
Knapp explained that freezing rain occurs when warm, moist air overrides cold air that's already in place at ground level. The upper air mass is the precipitation source. So, the moisture is liquid when it first falls. The rain starts to freeze, however, when it drops into the cold-air zone.
"With that kind of recipe, you've got quite a bit of room for variation," she said. "Des Moines, Iowa, established a record for being different on Dec. 21, 1990. The temperature was 2 degrees below zero. But, the moisture falling then was freezing drizzle-- in other words, still-liquid precipitation."
Another odd outcome can occur when the cold, lower air mass is sitting on ground that's warm.
"That's when you get icing on trees, fences and elevated surfaces--while little ice collects on roads," Knapp said. "Even then, however, the ice buildup can deposit tons of weight on tree branches. Ice on utility lines can result in power outages that take days to repair. Fires can soon be a problem, too."
Yet, the most treacherous combo for travelers can be ice, hidden under snow--in part because it starts out looking fairly harmless, she said. Once deposited, the mix also can be difficult to remove. And, as it melts, the snow can keep adding to the ice layer whenever nighttime temperatures fall below 32 F.
According to the National Weather Service, about 70 percent of Americans' winter storm-related injuries result from vehicle accidents. About 25 percent result from their being caught out in the storm.