Syracuse, NY – The first real taste of winter could bring “tremendous” lake effect snow to parts of upstate New York this weekend, the National Weather Service said.

More than a foot of lake effect snow is possible in typical lake effect areas near Lakes Erie and Ontario.

“Immense bands of snow and lake-effect snow showers will develop east and southeast of the Great Lakes, resulting in significant accumulations and blowing snow in the hardest hit areas,” the weather service said.

The worst spots are likely to be I-90 between Cleveland and Buffalo and I-81 north of Syracuse. Wind gusts of up to 30 miles per hour will cause poor visibility on the roads.

“Travel could be very difficult to impossible with very poor visibility and deep snow cover on the roads,” the weather service office in Buffalo said. “Some major roads may be temporarily closed.”

Winter storm warnings are in effect for these areas from Friday morning through Sunday morning. Monitoring areas include Cattaraugus, Chautauqua, Wyoming and southern Erie counties in western New York, south of Buffalo; and Oswego, Lewis and Jefferson counties on the Tug Hill plateau.

By Monday the wind could shift and come from the northwest. In this case, lake effect snow could extend from Georgian Bay to central New York and even the Southern Tier, the weather service said.

The exact locations of narrow lake effect snow bands are very difficult to predict several days in advance.

Late November and early December is peak season for lake effect snow as the Great Lakes are still warm and mostly ice-free. Cold winds blowing down from Canada pick up moisture from the warm lakes and drop it as snow as the winds blow over relatively colder land.

Lake Erie’s surface temperature is 51 degrees today, 6 degrees above the long-term average as of November 27th. Lake Ontario also has a temperature of 51 degrees, but the weather service does not keep historical data. That’s because Lake Ontario is so deep – up to 800 feet – that rising cold water during high winds causes wide temperature swings at the weather service’s official measuring point near Rochester.

Great Lakes surface temperature is a major factor in lake effect snow, but not the only one. To produce large lake effect snowstorms, the winds must be from the west or northwest and the air blowing over the lakes must be cold enough.