As strong high pressure retreats to the NE late Sat night into
Sunday, an expansive winter storm will impact the area from then
into Mon. Primary low pressure moving into the TN valley on Sunday
should dissipate while a secondary low forms near Cape Hatteras and
the VA capes, and then moves to a position just inside the 40N/70W
benchmark. Snow should begin in the NYC metro area after midnight
Sat night and spread NE to the rest of the CWA by daybreak, with
some accumulation of 1-2 inches possible by daybreak for the NYC
metro area. Heavy snow is then likely daytime Sunday into Sunday
evening via strong front-end H7-8 frontogenetic and thermal forcing
aided by an anticyclonic upper jet to the north. Given the cold air
mass in place, snow ratios look to be on the high side (15:1) at the
onset, and then settle down a little closer to 12:1 as heavier
precip arrives and the low to mid levels slowly warm.
Depending on the ultimate track of the system, it remains possible
enough warm air could intrude aloft to force a brief mix with sleet
and/or freezing rain Sunday night, especially for NYC and Long
Island. Have only mentioned a slight chance of this occurring, and
at any rate the damage will have been done well before then as far
as meeting 6+ inch snowfall amounts.
Total QPF for the event should be roughly between 1.0-1.5 inches.
Watch mentions a boilerplate 6-12 inches likely with localized
accumulations over 12 inches, but the above QPF with higher snow
ratios could yield widespread potential accumulations of over a
foot.