Is All That Ice Going To Knock Out My Power? The Weather Service Might Be Able To Tell

Crews work to repair power lines in Dickson County, following an ice storm in early December. Image: Dickson Electric System

The National Weather Service is trying something new this winter. Forecasters are telling Middle Tennesseans not just how much ice will fall in an ice storm, but if the power will go out and for how long.  The system could be useful one day, but right now it’s far from perfect.

So far, forecasters are good at the “if the power will go out” part. But “how long” is still a little fuzzy. Take the recent ice storm that hit Dickson County. The forecast predicted outages of just a few hours, but thousands of residents were in the dark for days. Here’s the problem: it’s hard to know how much ice is on the ground at a given time.

“If ice continues to accumulate, you have to take into account yesterday’s ice and the day before’s ice, all the ice until it melts off,” says Larry Vannozzi, who heads the Weather Service’s office in Nashville.

For the index to work better, Vannozzi says forecasters will need a better way to measure ice accumulation. Right now, the only way to do that is with the naked eye.

Middle Tennessee is one of about a dozen regions where the National Weather Service is testing the prediction model. That’s because we’re susceptible to ice storms—being far enough north to see ice during the winter but not too far south to get just rain.

An example of the ice storm impact forecast, from December 7. Known as SPIA, it grades ice storms on a scale from 1 to 5, with 5 being the most severe. Image: National Weather Service.