https://forecast.weather.gov/product.php?site=NWS&issuedby=O...

Confidence has increased enough to warrant winter storm watch issuance for the entire CWA. Latest 12Z guidance coming into better agreement on potent northern stream shortwave energy diving SW from wrn Canada and the northern Plains into the plains and mid Mississippi valley by Sunday morning, phasing with southern stream coming out of the SW states and Mexico to carve out a deep closed low aloft over the Mid Atlantic and induce rapid cyclogenesis off the Mid Atlantic coast, with the surface low bombing out from from 1008 mb off the N Carolina coast Sunday morning to 970-975 mb near 38-39N/71W by Monday morning, then passing just outside the 40N/70W benchmark Monday afternoon, GFS still more intense and closer to the coast than the ECMWF, with its heaviest snow bands directly over the area as opposed to just offshore. NAM and SREF have both trended toward a heavier snowfall scenario as well, which has been a good signal in past heavy snowfall events.

Snow should start Sunday morning, and may mix with rain at times especially in the NYC metro area, NE NJ and western Long Island. Then as precip intensity picks up later in the day Sunday p-type should become all snow throughout. Heaviest snow looks to fall from late day Sunday into Monday morning, then snow tapers off Monday afternoon.

Greatest likelihood of seeing 6+ inches will be along the coast, especially eastern Long Island where up to a foot of accumulation is possible. Winds will also be strong Sunday night into Monday morning especially along the coast as the sfc low deepens, with blowing and drifting snow and some downed tree limbs as winds gust to at least 40-45 mph, and possible blizzard conditions in Suffolk, and near blizzard conditions elsewhere along the coast including NYC. NAM/GFS both signal potential for wind gusts to 60 mph late Sunday night into Monday morning, though these winds can sometimes be overdone in heavy snow events. If trends for heavy snow and strong winds continue to increase and expand northward, the potential for blizzard conditions could encompass all coastal areas.