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Weather in Action: Upstream Lake Effect Snow Bands
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Aftermath of a lake effect snow event
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The National Weather Service has been studying lake effect snow (LES) for many years. LES events occur to
varying degrees on all of the Great Lakes as well as other bodies of water such as the Great Salt Lake in
Utah. Research efforts have given meteorologists a good basic understanding of
LES fundamentals especially
in regards to which wind directions and temperature profiles are conducive to LES. For the most part
LES events are single lake events with bands of snow off of Lake Ontario, bands of snow off of
Lake Erie, etc. However, when atmospheric parameters are favorable multiple LES bands from different
lakes can merge and enhance snow fall rates farther downstream
The radar picture below is a composite image from the neighboring radars in Buffalo, NY and
Binghamton, NY during a LES event. A single band of LES is clearly visible downwind of Lake
Ontario extending southeastward into the Syracuse area. Yet the plume clearly has origins
beyond Lake Ontario since the westernmost portion of the band viewable on the radar extends
across southern Ontario, Canada.
By looking at the visible satellite picture below we can see what is happening. A single band of
LES has also formed over Lake Huron, upstream of the Lake Ontario band. The wind direction was just
right across the lakes to allow the bands to merge into a large LES band complex spanning several
hundred miles, with the band over Lake Huron feeding into the band over Lake Ontario. Having an
upstream LES band reinforce another band farther downstream makes the downstream band a better snow
producer than it would have been by itself.
This particular case occurred in late March. LES bands typically lose their identity and become more
cellular as a result of heating during the afternoon especially early and late in the season. By having
an upstream band for reinforcement, the single band downwind of Lake Ontario was able to maintain its
integrity throughout the afternoon despite relatively strong insolation.
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