November 11, 1996 13Z
surface data analysis
By the early morning hours of Nov 11, 1996 heavy snow is falling in
many of the snowbelt communities from western New York, NW Pennsylvania,
and points west. Unseasonably cold air (note the low 20's in west central
Ohio) is pouring into the region on brisk west and northwesterly flow.
However, close to the warm lakes, surface temperatures warm as can be seen
by following the 28F isotherm around Lake Erie and Ontario.
||In the pressure field,
the surface low
responsible for the heavy snowfall
of Saturday Nov 9 has lifted into Ontario Province and weakened. The
associated cold front
has made little progress eastward because the upper
level trough is aligned with the surface front and does not provide any
eastward push to the system. "thermal troughs" have set up east of Lakes
Superior and Michigan.|
The flow field shows an ideal fetch for lake effect snow in NE Ohio and
the downwind shore of Lake Erie. The fetch of cold air over southern Lake
Michigan turns cyclonically from NW to westerly as it crosses the western
end of Lake Erie.
||It appears that the thermal trough in evidence east of
Lake Michigan is important in backing the flow between the two lakes.
This trajectory across the two lakes implies that air arriving over Lake
Erie will have been "preconditioned" with heat and moisture from Lake
Michigan - thus, making it easier for clouds and precipitation to quickly
form to the lee of the lakeshore.|
Nov 10, 1996 10Z
Nov 11, 1996 19z