Lake-Effect Snow to Blast Great Lakes Region

In the wake of Winter Storm Dion, a frigid air mass is setting off the season's heaviest lake-effect snows to date across parts of the Great Lakes region.

(MORE: Current Winter Weather Alerts | Latest Updates)

Wednesday Winds

Cold Wednesday

Cold Thursday

Western Great Lakes

Eastern Great Lakes

As cold winds blow across the relatively warm waters of the Great Lakes, they are picking up moisture. That moisture, in turn, is being wrung out on the lee side of the lakes in the form of locally intense bands of snow.

For Wednesday and Thursday, very cold air – with temperatures near zero 5,000 feet above the ground – will be crossing the open lakes, where water temperatures are in the mid 30s to low 40s. The temperature difference between the air and water has created instability in the atmosphere, allowing moist air near the lake surface to rise, forming clouds and snow squalls.

(INTERACTIVE: Great Lakes Radar)

"Fetch" is the technical term for the distance over which wind crosses open water. When the wind blows down the long axis of one of the Great Lakes, snowfall potential is maximized on the lee side of that lake. In this case, it looks like three areas will have a favorable fetch:

• East of Lake Ontario over the Tug Hill Plateau in upstate New York, north of Syracuse
• East of Lake Erie over southwest New York, mainly south of Buffalo
• East of Lake Huron's Georgian Bay over Ontario province of Canada, as a long fetch of wind crosses Lake Superior and northern Lake Huron

At this time, at least within the U.S., it appears that the heaviest snow totals will be found east of Lake Ontario, where the favorable fetch and the sharp rise in elevation east of the lake will contribute to storm total accumulations of over 3 feet on the Tug Hill Plateau through early Thursday. As of early Thursday morning, 28 inches of snow had piled up east of Lake Ontario in Lacona.

(FORECAST: Syracuse | Watertown | Lowville)

As the inset maps show, significant snowfall will also affect the ski country south of Buffalo as well as the shores of Lake Superior in Michigan's Upper Peninsula.

(FORECAST: Jamestown, N.Y. | Marquette, Mich.)

For Lower Michigan, the dominant westerly winds will blow perpendicular to Lake Michigan's axis, leading to multiple bands of less intense lake-effect snow. Still, snow and blowing snow will reduce visibilities especially along and west of U.S. Highway 131, as is typical of this kind of setup.

(FORECAST: Traverse City | Grand Rapids)

Across this entire region, the very cold conditions will lead to snow-covered and icy secondary roads and side streets, and even well-traveled and well-treated roadways may have slick spots. Drive with caution and have a winter weather survival kit with you if you are traveling longer distances between cities.

http://www.weather.com/news/weather-winter/lake-effect-snow-blast-great-lakes-region-20131210