The science of lake-effect snow
By Jared Shelton News-Press NOW meteorologist
The first snowflakes of the season fell over parts of Northwest Missouri and Northeast Kansas last weekend, amounting to only a trace of accumulation in St. Joseph, where a light dusting of white coated parts of the landscape for just a few short hours.
Meanwhile, enough snow came down to produce a winter wonderland 20 to 40 miles south of St. Joseph, as a narrow band of precipitation dumped 2 to 4 inches of wet snow along and just north of the Interstate 70 corridor. Isolated locations even picked up on 5 inches of fresh snowfall, catching many off guard.
When it comes to winter weather, sometimes a few miles can make all the difference. This could not be more true for those subject to bands of blinding lake-effect snow, which pummel select locations downwind of the Great Lakes every year, particularly in late fall and early winter before Lake Michigan, Lake Superior, Lake Ontario and Lake Erie are cold enough to freeze over.
Different from typical snowstorms, which dump snow over large regions spanning thousands of square miles and even entire states, lake-effect snow often comes down in narrow bands that can be less than 10 miles wide but up to 200 miles long. As frigid air blows over the unfrozen Great Lakes in late fall and early winter, it can tap into the relatively warmer waters, developing a convective corridor of intense snowfall. Lake-effect snow squalls can even produce thunder and lightning, almost like a summer storm that brings blinding rain in one part of town and leaves other nearby areas completely untouched.
Aside from “warm” lake water and a steady stream of polar air, a few other factors influence when and where the most intense lake-effect snow bands develop. The orientation, or “fetch,” of polar air blowing across the Great Lakes can maximize the intensity and longevity of a snowsquall when it passes over long stretches of open water.
For example, parts of western New York are pummeled with the worst of lake-effect snow when winds are west to east, blowing longways across Lake Erie with a fetch of over 100 miles.
Geography also can play a role in lake-effect snow, as small mountains and other elevated areas can provide more lift for powerful bands to develop and thrive with maximum efficiency. The Tug-Hill plateau along the shores of Lake Ontario in northern New York knows this all too well, where a handful of world-record snowfall events have taken place over the past century and the annual average snowfall ranges from 200 to 250 inches per year.
For the past seven to 10 days, lake-effect snow has made national news, pummeling parts of the Great Lakes region as some unlucky locations have picked up on 30 to 60 inches of snow. The list of those now buried under 4 to 6 feet of lake-effect powder includes parts of upstate New York, northern Michigan, northwest Pennsylvania and northeast Ohio.
