Back-to-back winter storms in the Triad and High Country recently brought record snowfall to the region. But accumulation results can vary greatly.
So, how exactly do weather forecasters come up with those totals?
Trained observers make the official calculations. First, they need an open area away from buildings or trees to take measurements. In central North Carolina, that’s the airports in Greensboro and Raleigh/Durham. Normally, snowfall is measured on a flat, white “snowboard” that’s about 24 by 30 inches.
Chrissy Anderson is a meteorologist at the National Weather Service in Raleigh. She says observers use a standard snowfall measuring stick and take readings at regular 6-hour intervals.
But what happens when it’s windy?
"So, the last storm, January 30 to the 1st, there was significant blowing when it was snowing, and that caused drifting snow, which really made it difficult to get an accurate measurement from just one board," said Anderson. "So that's when the observers at the airports put out multiple snowboards, and they measure multiple locations around the airport, usually about five to 10 spots, and then they calculate an average."
Anderson says that average they calculated during the most recent weather event became the official snowfall total of 10.4 inches for the Greensboro airport area.
And what about ice totals?
"So for ice accumulation, it's a little bit different," she said. "It's measured automatically by sensors at the airport's automated surface observing system."
Anderson says in some cases with ice, National Weather Service observers can also visit sites to monitor thickness. She says to confirm amounts, they look at trees, branches, roadways and cars.