How does the National Weather Service forecast LES?
National Weather Service (NWS) meteorologists must consider many factors when forecasting the intensity and location of LES. Many are associated with the prevailing meteorological situation, while others are a function of the local geography. A few of the meteorological factors that impact LES include air temperature, instability (as approximated by the lake to air temperature difference), cold air depth (inversion height), upstream moisture (relative humidity), large-scale lift, and winds. The physical geography of the land and water is also important; including aspects such as fetch, elevation, and shoreline orientation. One of the more challenging aspects of forecasting LES is pinpointing where the heaviest snow will occur. Even small changes in wind direction can change tremendously the areas impacted. The following table shows which areas typically receive the heaviest snowfall, as a function of wind direction. Though LES can occur with any wind direction, it is most common when w
