How snowfall is measured

Ask any two neighbors to stick a ruler in the ground and measure this week’s snowfall, and they will probably end up with different numbers. WHYY has more on how the data collectors measure the final tally.

Ask any two neighbors to stick a ruler in the ground and measure this week’s snowfall, and they will probably end up with different numbers. WHYY’s health and science reporter Kerry Grens has more on how the data collectors measure the final tally. [audio:100211kgsnow.mp3]

Ever wonder where snow accumulation totals come from?

Predicting snow fall is a complicated science, but measuring that snow fall is pretty low-tech. The National Weather Service is the official flake counter. Observers at the airports and volunteers around the region take snow measurements. Joe Miketta is a meteorologist at the National Weather Service’s Mount Holly station.

Miketta: They actually put a board on the ground in an area where it doesn’t normally drift and it’s not blocked by any obstruction and an observer goes out every six hours and actually measures the depth of the snow. And then they wipe the board off so they can get a new measurement six hours later.

Miketta says the measurements are often not exact — take a situation like Wednesday morning, where rain fell and melted some snowpack before the storm’s second wave brought more snow.

Miketta: So it’s actually possible if the conditions are right that a snow pack can go down even though it doesn’t stop snowing. And that makes figuring out how deep the snow gets very very interesting.

The weather service also measures the total liquid precipitation by taking a core sample and melting the snow. Miketta says that helps predict whether snow melt will cause a flood. This week’s storm measured between one and two inches of water.