Lake-Effect Snow Guns Start Up

Lake-effect snowstorms often run at full throttle in December. That's becausethe temperature of the Great Lakes is relatively mild compared to the arcticair masses that might be crossing them. What this produces is a very unstableatmosphere. The low levels gain a little heat from the lakes, while it remainsvery cold aloft. This causes large bodies of air to rise abruptly, formingclouds and snow. The snow often falls in narrow bands that are strung out inthe direction of the wind. Often some of the worst lake-effect snowstormsresult from bands that are barely 10 miles wide. The trick is keeping the bandover one location for a length of time, and if that happens, you can gettremendous snowfalls. Given the most extreme situations, lake-effect storms cangenerate snowfall at the rate of 4 or 5 inches per hour!Currently, we are dealing with a very extreme situation. The air that will becrossing the Great Lakes on Thursday is very cold, which will create a veryviolent condition in the atmosphere. The bands of snow that stream downwind ofthe lakes into Friday will produce snowfall totals of 1 to 3 feet!Story by AccuWeather.com Senior Meteorologist John Kocet.