Later Saturday afternoon through Saturday night the closed low will
move over or just south of the eastern Great Lakes. The associated
pool of cold air aloft will move overhead, and modest cold advection
will begin in the boundary layer. This will allow for a change to
wet snow, first at higher elevations where temperatures will be
slightly cooler, and last near the Lake Erie and Lake Ontario
shorelines. The majority of the precipitation will then be snow
later Saturday night through Sunday, although some rain may still
mix in at times across lower elevations. The wrap around phase of
precipitation Sunday and Sunday night will feature upslope
enhancement across the higher terrain of the western Southern Tier
and Tug Hill region as westerly flow increases in the wake of the
system. While there will be orographic enhancement, the boundary
layer never becomes cold enough for any appreciable lake
enhancement.
As far as accumulations go, the marginal thermal structure will
likely keep the accumulations highly dependent on elevation. There
will be virtually no accumulation anywhere through late afternoon
Saturday. Saturday night and Sunday it will become cold enough
across higher terrain to allow for accumulation to begin. Expect
total accumulations from Saturday night through Sunday to reach 3-6
inches across the higher terrain from the Boston Hills and Wyoming
County down through Chautauqua and Cattaraugus counties, and also on
the Tug Hill Plateau. Across lower elevations, temperatures will
struggle to get cold enough to allow for much, if any accumulation.
Expect a coating to an inch or two of slush at most across most of
the lower elevation locations, including Buffalo and Rochester.
These are early estimates and may change with later model guidance.