Arctic or polar continental air masses
cross the warm lake. The cold airmass is usually only a few thousand
feet thick, and is "capped" by a layer of warmer air, called a temperature
inversion. This inversion limits the extent to which the snow clouds
can grow. The addition of heat and moisture from the warm lake modifies
the airmass and modified air rises and cools allowing moisture to condense
into snow clouds. It also causes the inversion to raise, allowing
snow clouds to grow in height. After moving easily across the "smooth"
lake surface, the modified air slows down and "piles up" as it approaches
the downwind shore. The convergence produces additional lift, which
is further enhanced by orographic features (hills, mountains) downwind
of the body of water. The result is lake effect snow, though during
early Fall, lake effect
rain can occur.