CAPE

It's a delicate balance. The vorticity feeding the gyre is what flattens the flow and de-amplifies the wave enough to force it to track underneath.

Something to note about the synoptic setup for this storm is the absence of high pressure to the north. Without that feature in place we don't want to see the initial low become too amped and tracking to our NW with no wedge in place. Nice to see the GFS depiction of a weaker low as it tracks into WV with a secondary low to our south becoming more prominent.

This is the modeled snow from the 6z GFS for today so factor that in the the snow total maps.

GFS is adjusting towards the other guidance. Less amplified/weaker with the initial low and earlier secondary development.

6z GFS coming in souther.

Icon never leads the way. GFS is always wonky to some extent. This is exactly the sort of progression we want.

Like I said, Euro, as expected, is rock steady. Weenies happy again. Drink. ( I'm drunk)

Gorgeous. It looks like a brief relax in the block, with another episode developing, originating more from Scandinavia this time. Ens means have been hinting at this. NA blocks that evolve from Scandi ridging excite me.. 2009-10.

Look above. Strong jet streak increases vorticity below.

Yeah its not out yet. My post was in anticipation of it holding steady vs the apparent ICON led north trend, with the GFS also going that way. These run to run variations always happen at this range, and many folks seem to lose sight of the big picture. This pattern is supportive of a significant frozen event across the region, and its happening.

Not on WB

18z Euro, ever rock steady- the voice of reason- will stop the mini weenie panic lol. I never set a bar, so the previous simulations that produced 8-12" for my yard are just that. Pretty sure its gonna snow.

Looks a little wonky to me. Only very subtle differences at h5. Run to run change is nada from 12z to 18z. Chalk it up to 'noise', but given the relatively narrow N-S area where parameters align for heavy snow, pretty small changes can make a notable difference. This is how we roll almost always!

Eh I will take 12z all day over this run verbatim lol. Very nice run for the southern PA folks though.

GFS hangs onto the primarily low. Did this a bit at 12z but a little more pronounced this run. Not sure I buy it. Either way not a huge difference but explains some of the mixy issues getting closer for a time.

WWA up here for tomorrow for snow accumulation less than one inch tomorrow, and less than one inch tomorrow night. I expected 'half inch or less' wording, but ok. Mt Holly Kinda bullish- The bulk of the snow will fall across the Delaware Valley, including Philadelphia and nearby suburbs, southern New Jersey, and Delmarva. In these areas, around an inch to two inches of snow will accumulate. Will go ahead and issue an impact-based Winter Weather Advisory for these areas mostly since the bulk of this snow will fall around the time of the evening commute. A coating to under an inch of snow is possible north of Philadelphia.

Actual total eta- SBY to OC an inch+ is from the tomorrow night thing Same for N MD and DE on the GFS map

That's the way I would interpret it if you're referring to the GFS. The 6z Euro actually partially phases a piece of that NS energy.

The 0z Canadian tracks the primary low further north than current runs of the GFS and Euro. Part of the reason has to do with that shortwave tracking southeastward in southern Canada I mentioned in an earlier post- look where the CMC has that NS energy as the storm is approaching. Notably further north than other guidance at that point. Results in weaker confluence and allows the low to come further north.

The run to run variations on the storm track we are seeing on guidance are pretty minor, but for those on the N or S edge it can make a big difference. The primary feature to watch is the piece of vorticity rotating down in southern Canada overtop our approaching shortwave. Some runs it digs a bit more, or comes in right on top or out in front/just behind. The timing and degree of interaction between that energy and our storm will influence the exact track.

Hints of a little enhanced lift on the west side of the developing offshore low via an inverted trough

Latest Natty blend

The advertised look for mid month looks prime for a major east coast snowstorm. The 0z GEFS 13-16th window is active.