From the National Weather Service in Buffalo:
.LONG TERM /WEDNESDAY THROUGH SATURDAY/... ...Some Accumulating Wet Snow Increasingly Likely by the Weekend... It`s been a long time in coming...but it is starting to look more likely that most of the region will pick up their first measurable snowfall of the young season during this period. A large and very complex storm system will develop over the Mid west... and while the various guidance packages continue to have run to run variability...a general agreement is taking shape for a prolonged period of precipitation that should include some wet snow. The highest chance for the wet snow will initially come at night and across the higher terrain...but as we approach the weekend...the mixed pcpn/wet snow should become more widespread with lake enhancement figuring into the equation as well. While confidence remains low with many of the details...including snowfall amounts...it is not out the realm of possibilities that lake enhanced areas southeast of the lakes pick up several inches of wet snow by late Saturday. A vigorous 140kt H25 jet digging into an already impressively deep longwave trough over the nations mid section on Wednesday will lead to significant hgt falls downstream across the Lower Great Lakes and especially the Mid Atlantic region with broad areas experiencing return intervals greater than once in a generation (25-30 years) for this time of year. This will easily support broad cyclogenesis from our forecast area to the Mid Atlantic coast with deep moisture allowing for widespread pcpn for much of this period. The day to day details... While broad cyclogenesis will be taking place immediately to our west on Wednesday...a stubborn mid level ridge will help to keep fairly innocent weather in place for the bulk of our forecast area. A nearly stalled warm front/triple point will extend from Lake Erie southward across western Pennsylvania...but there should be enough forcing to allow for more nuisance rain shower...mainly over the western counties. The bulk of the day should be rain free. This will all change Wednesday night...as the still deepening closed storm system will dig across the Upper Great Lakes. The downstream ridge will finally be shoved off the coast...and this will allow an occlusion to sweep northeast across our forecast area. Deep lift supplied from combined H925-70 frontogenetic forcing and from a passing 100kt H25 jetlet will support a wide swath of moderately heavy rain over our area. Rainfall Wednesday night should average a half to as much as one inch by daybreak. Given our dry antecedent conditions... this will be beneficial rain and should NOT be an issue. An important difference from previous guidance though is that a somewhat more northerly placement of the stacked mature low will encourage colder air to sweep into the region...particularly the western Southern Tier. This would allow the rain to mix with...and possibly change to...wet snow by daybreak Thursday. Confidence will deteriorate somewhat on Thursday as to where the large lumbering storm system will track...either to the southeast to about West Virginia or to remain nearly stationary over the Lower Great Lakes. In either case...relatively deep moisture will remain in place on Thursday with any dry slots being SHORT LIVED in mature. Colder air will continue to seep into the region at this point...and with H85 temps generally ranging from -2 to -4c...at least some of the resulting rain will fall as a mix. Mainly just wet snow will be likely across the higher terrain and in areas where the pcpn can be steady enough to support dynamic cooling (in this cooling due to melting) for just wet snow. Minor accumulations will be possible in these areas...especially on elevated surfaces. From Thursday night into Saturday...guidance is somewhat in line with additional shortwave energy feeding into the large closed storm system. This would encourage the stacked low to dumbbell from the Mid Atlantic region up across New England. The deep cyclonic flow would remain firmly in place over our forecast area...with H85 temps of -2 to -4c and deep synoptic moisture supporting continued CAT pops for mixed pcpn. By the weekend...a north to northwest flow would then offer some lake enhancement as well. This 36 to 48 hour period should allow just about all of the region to experience a little wet snow...with many areas increasingly likely to pick up a some accumulation. Given the relatively `warm` antecedent conditions though...most areas are not expected to experience problems with area roadways. This would only change if it were a little colder aloft to allow for more prolonged snowfall.