Cold air advection will start to change the rain to snow as early as
Saturday afternoon, especially at higher elevations of the western
Southern Tier, as the surface low tracks north into southern Quebec
by Saturday evening. The low will continue to push northward while
deepening, pulling down much colder air behind it. This will
eventually change all the precipitation over to snow by Sunday. The
cold advection will lead to a period of lake enhanced snows east of
the lakes, before the synoptic moisture gets cut off by approaching
surface high pressure from the Ohio valley Sunday night.
The highest snow accumulations are expected across the higher
terrain east of the lakes where the change over to snow occurs the
quickest and lake enhancement occurs. In these areas, could be
looking at amounts as high as 4-6 inches, perhaps as much as 3-4
inches across the Bristol Hills. Temperatures will remain marginal
at lower elevations with accumulations likely limited to an inch or
less.