You can’t turn on the news today, or over the past few days, without hearing about the bitter cold now underway from the Plains to the Mid-Atlantic and New England. As I watched the “Today Show” yesterday morning the cold was such a great lead-off story that hosts Matt Lauer and Savannah Guthrie started the show outside, as bundled up as they could be. Oddly — but appropriately enough — Al Roker was inside with a cup of something hot and steamy. But it’s January, after all, and this is part of the deal (except on the Gulf Coast where we came close to 80 yesterday in Houston and will do the same today).
However, because it’s January there’s still a lot of winter yet to come and some of it next week will be none too pretty. And what could be worse than bitter, miserable cold? What could be worse than heavy snowfall or even a blizzard? What’s the worst winter can throw at us? Ice. For northern regions of the country, really any region of the country, an ice storm can be as devastating as a hurricane in many regards. Enough ice can bring down trees which can then bring down power lines which can then lead to hundreds of thousands of people being without power, to say nothing of the treacherous travel conditions. Following an ice storm, travel conditions remain dangerous which makes repairs to property and the power grid excruciatingly slow.
It was four years ago this month when a winter storm brought two inches of ice accumulation and then as much as five inches of snow on top of the ice to the central Plains and Midwest. The one-two winter punch left two million people without power and was responsible for 55 deaths.
And so as we look at the situation developing next week, even though the risk at this time is classified as slight, we can’t afford to downplay the potential for significant consequences. So here’s what’s happening.
First, a warm-up. Any icing situation needs warm air over sub-freezing air to allow liquid precipitation in the elevated warm air to freeze or begin to freeze as it falls through the colder air near the surface. That is indeed the case: high temperatures today in the lower 20s will warm to nearly 40 by Monday in places like Indianapolis and Columbus.
Next, moisture. There has to be precipitation, not just heavy clouds and gusty winds. The more precipitation available, the more ice accumulation possible. The icing on the cake (sorry) however, is a sudden drop in temperature while the precipitation is occurring. What starts as rain ends up as ice on the ground.
All these factors will be in place later this weekend as the next cold front will deliver a chilly blast to the Midwest. Behind the cold front, cold air will undercut the already-in-place warm air, creating the ideal conditions for accumulating ice as liquid precipitation aloft falls through sub-freezing air near the surface.
[The video of the English people doing the best they can to traverse an icy street can be seen here.]