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November 10th 1996, 04Z
surface data analysis
A surface low in northwest Pennslvania (PA)
is producing and
area of snow and rain in the
eastern lakes. The cold front associated with
the low is the leading edge
of the unseasonably cold air which set-off the LES event that persisted
through the next three days.
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At 0400z on November 10 (i.e. late evening on the 9th of Nov), NE Ohio
was receiving locally heavy snowfall as a result of the surface storm.
At this hour snow was falling at the rate of 1-2"/hour in the higher
elevations east and southeast of Cleveland, Ohio. Temperatures were
hovering near freezing, as can be seen in the 32F isotherm highlighted below.
Warmer
air is being wrapped around the backside of the storm through the eastern
lakes. |
Most accounts of this phase of the storm attributed the heavy snowfall in
NE Ohio to the elevation of the terrain and the flow of unstable air over
the east end of Lake Erie. Winds were weak in this area, but were both
convergent and over water. This "lake-enhanced" snowfall produced a great
variation of snowfall in the region. Some local snowfalls of 14" were
reported in Geauga county, while nearby communities had only wet snow
without accumulation. There is some question whether this was a
"lake-enhanced" storm since the flow was quite weak and the air flowing
over the open waters was not very cold. However, the lake temperature in
eastern Lake Erie is very warm (>55F) so there is an appreciable
difference between the water temperature and the air blowing across the
lake. The distribution of snowfall certainly suggests lake-enhancement.
[Image: P,T, Wx 11/10/96 04z (66K)]
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In the western lakes, much colder air is moving into upper Michigan
and Wisconsin, and is setting off lake effect snow south of Lake Superior
and east of Lake Michigan. The dotted red lines denote thermal troughs in
the vicinity of the warm lakes. These troughs are important in
redirecting air flow and creating surface convergence near and east of the
trough axes. The troughs are found in most of the following surface
analyses and remain fairly stationary throughout the duration of the
storm. |
introduction
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Nov 10, 1996 10Z
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