The lake effect is particularly clear in this Sea-viewing Wide
field-of-view Sensor (SeaWiFS) true-color image of the North American
Great Lakes region, acquired December 5, 2000. Lakes Nipigon, Superior,
and Michigan show striking contrasts between clear and cloudy air as the
wind blows from the northwest across the lakes.
As it flows across the relatively warm lakes, the cold dry air gathers
heat and moisture from the surface. The warm moist air rises into the
atmosphere and mixes vigorously with the cold dry air above. The layer
of warm moist air deepens as it travels across the lake. Some of the
evaporated water from the lake condenses into streamers of fog rising
from the surface, while much of the moisture condenses to form a
stratocumulus cloud in the upper half of the mixed layer.
The cloud-forming water droplets may freeze into ice crystals and, due
to accumulated water deposition over time, grow into snowflakes. This
process can generate snowstorms that produce significant amounts of
snowfall downwind. It is not uncommon for lake effect snowstorms to
produce as much as two feet of snow within a 24-hour period in
northwestern parts of New York and Pennsylvania.
Image provided by the SeaWiFS Project, NASA/Goddard Space Flight Center,