Accumulating snow likely Friday night and Saturday...
Widespread snowfall event expected Friday night through Saturday,
with some additional snowfall expected from northwest flow lake
effect Saturday night. Two separate shortwaves, one within the
southern stream and the other within the northern stream will be
head eastward Friday night. These features will eventually phase
over the mid Atlantic and Northeast by Saturday. In response, low
pressure will develop Friday night over the southern Appalachians.
This low will then strengthen and track up along the East Coast into
New England Saturday.
Surface temperatures early Friday evening will likely still be warm
enough to support rain or a rain/snow mix across much of the area
ahead of the approaching cold front. The exception may be across
portions of the Niagara frontier and closer to Lake Erie where the
start of wet-bulbing may have already transitioned the rain over to
wet snow. The surface cold front will cross the area from west to
east early Friday night. Once the boundary passes, any rain will
transition to snow very quickly and pick up in intensity. The
expectation is that by midnight or so Friday night that the entire
area will have transitioned over to wet snow.
Steady light to occasionally moderate snow will continue across the
entire area through the first half of Saturday. Snowfall rates are
not likely to exceed more than a half inch per hour. Although, there
is the possibility for some mesoscale banding on the western side
of the storm, as strong frontogenesis is expected due to the rapidly
deepening low which may bring enhanced snowfall rates.
Later Saturday afternoon and Saturday night as the storm starts to
pull off, lake enhanced snow will eventually go to pure lake effect
snow as 850 mb temperatures near -18C. This will maintain snowfall
to the southeast of the lakes and higher terrain.
As the storm deepens as it lifts into northern New England, winds
will increase with wind gusts of 40-45 mph possible Saturday into
Saturday night which will result in considerable blowing and
drifting snow with potential near white-out conditions at times.
The greatest snowfall totals continue to look to be focused east of
the Genesee Valley and also across the higher terrain east and south
of Buffalo off Lake Erie due to lake enhancement/upslope flow. These
areas are included in a winter storm watch as outlined below, not
only for snowfall of 7 inches or more, but also with the added
impacts due to the strong winds.