This time of year the word "snow" starts to get mentioned in forecasts, and one particular breed of snowstorm gets a lot of attention. That's the so-called "lake-effect" snow.

These localized snows form when cold air from Canada flows across the waters of the Great Lakes, which are still relatively warm this time of year. The air warms, moistens, rises and forms clouds, which then dump bands of heavy snow just to the south and east of the Lakes. Here's a satellite image taken the day after a lake-effect snowstorm a few years ago - the white areas south and east of Lakes Erie, Ontario, and Huron are snow-covered and are typical lake-effect zones.

Closer to home, northwest winds here are coming down out of the Appalachians, and sinking air tends to dissipate clouds. As a result, it's unusual to see any more than a few clouds and snow flurries in the Philadelphia and Wilmington areas from the lake-effect.