From National Geographic: Geography in the News: Lake-Effect Snow
Lake-effect snow has arrived around the Great Lakes as winter has finally come to the Midwest.
During a single 1995 December storm, Buffalo, N.Y., received 40
inches of snow. Although this was a heavy snow, it was not a record for
Buffalo. Buffalo’s geographic location places it in position to receive
some of the Eastern United States’ heaviest urban snowfalls. The ring of
snowfall that occurs around the east side of the Great Lakes is a
phenomenon called lake‑effect snow.
Buffalo is located on the eastern shore of Lake Erie in western New
York State. The city is on a relatively flat glacial lake plain, to the
northwest of the Allegheny portion of the Appalachian Plateau. The plain
formed when a remnant of the Pleistocene continental glacier blocked
the northern drainage of the St. Lawrence River, backing up water into a
huge ice-dammed lake..
The lake finally spilled through the Mohawk Valley into the Hudson
River Valley and exited at present‑day New York City. The valley became a
glacial spillway. Today it is a broad, flat valley occupied by the tiny
Buffalo’s growth was stimulated by its location at the eastern end of
Lake Erie and at the western end of the Mohawk Valley. The Erie Canal,
following the Mohawk, was completed in 1825 and served as a water link
between New York City and Buffalo. Freight rates for shipping between
Buffalo and New York City immediately dropped by 95 percent and travel
time between the two cities decreased by more than half. This meant that
nearly all goods traveling by land or water between New York City and
the Midwest had to go through Buffalo.
Despite deep snows and winter winds from the lake, Buffalo ‑‑ today a city of more than 621,000 people ‑‑ grew and prospered.
One look at a map of the region confirms that Buffalo is the only
major city on an eastern shore of one of the Great Lakes. In fact, only a
few small towns are found on the east sides of the lakes. Snowy winters
and high lake winds are common in these locations, largely as a result
of a lake‑effect.
Lake‑effect snows result from cold, dry winter winds sweeping from
Canada across unfrozen lakes. As they cross open water, the winds
evaporate some moisture and become warmer. When the moist air reaches
the east sides of the lakes, the air is forced to rise abruptly over the
land and the colder air above the land. The results are exceptional
snowfalls in bands along the southeast sides of the lakes, often
accompanied by the unusual winter phenomena of thunder and lightning.
The most dramatic effect normally extends up to 70 miles (113 km)
inland from the lakes, but bands of light snow and flurries may extend
as far away as the ski resort at Snowshoe, W.Va., on the Appalachian
Most winter air from Canada is very dry and generally brings only
flurries, except on the leeward sides of the unfrozen Great Lakes.
Moisture for most heavy snowfalls in the Eastern United States ‑‑
outside of the areas having lake‑effect snows ‑‑ comes from the Gulf of
Mexico and the Atlantic Ocean.
Lake‑effect snows around the Great Lakes begin to cease when the
Great Lakes mostly freeze over, usually by February. An interesting
feature about the freezing of lakes is that all the water in the lake
must cool to 39 degrees F (4 C) before the surface can cool to 32 F (0
C) and freeze. The result is that a shallow lake–such as Lake Erie, the
shallowest of the five lakes–freezes over earlier and more frequently
than the other Great Lakes.
Buffalo’s average annual snowfall is nearly 100 inches (2.5 m), but
some surprising snowfalls have taken place in lake‑effect locations. For
example, Oswego, near the east end of Lake Ontario, received 101 inches
(2.56 m) in five days in 1966. Buffalo received 48 inches (1.2 m) in
one day in 1937. During the blizzard of 1977, Buffalo received over 120
inches (3 m) by the end of January, with February and March yet to go.
Few who have witnessed a heavy Buffalo snowfall accompanied by thunder and lightning ever forget it.