As of this posting (late Sunday afternoon), a Lake Effect Snow Watch has been elevated to a WARNING for Erie, Genesee, Wyoming, Chautauqua, and Cattaraugus Counties. This has the hallmarks of a true major winter event and will be highly disruptive due to rather strong winds creating near blizzard conditions within the movable feast of snow. (All this will be preceded by a few inches of water laden snow late Sunday into Monday afternoon, although there is still some chance of rain mixing in with that slushy snow at times).
BUFKIT and other models are showing Extreme instability from late Monday night into Tuesday, which virtually assures occasional thundersnow and locally very heavy snowfall rates. The lake snow will probably start over the hilly terrain Monday evening and shift northward through the Buffalo Stowns and into the rest of the metro area by Tuesday morning out to at least Batavia as the flow backs from W to SW. There are more indications as of this posting that enough backing of the boundary layer flow will occur for the LES to reach into the Ntown & NE ‘burbs, as well as the City (backing to 240 now indicated in the higher res NAM.). In a synoptic setup such as this (as noted by NWS AFDs), the climatological positioning of the 850mb low is favorable for such backing and for accelerated gusts. The passage of a short waves (I posted this in the previous thread) during Tuesday will allow some veering during Tuesday afternoon and evening back through the Stowns and into Ski Country. Winds are still likely to back to SW again by Wednesday AM, bringing LES back north. Rh values should diminish somewhat by Wednesday afternoon (along with some anticyclonic curvature around the ridge to our south), gradually lessening snowfall rates. Also as previously noted, another vigorous short wave will approach late Wednesday into Thursday, bringing more synoptic snow showers and some developing LES. The cold air trailing this low appears to be colder than in runs over the last few days, so some of that LES MAY be fairly impressive again if there isn’t too much directional shear–which can’t be determined this far out.
Bottom line: Confidence is High that this will be a major event. Confidence is growing that the metro area will suffer a big impact toward and through Tuesday morning, with veering returning a major impact through the Buffalo Stowns and then down into Ski Country by late Tuesday/Tuesday evening. Confidence is moderate and growing that the nearby northern and NE ‘burbs will also have a substantial impact. And, confidence is High that within this band Near Blizzard conditions will occur.