The GFS continues the idea of a significant storm system off the Eastern US.  The model does bring snow to the big cities but the heaviest snow stays north where New England is the jackpot on this run.  The GFS is rather generous for our area verbatim as it should be warmer and slightly further north with the sfc low but details like that are not big 180hrs out.  Also subtle changes which we think will occur will impact the GFS.

Two things I point out above are the placement of the sfc low and the arctic s/w.  Two are very important in determining who gets rain and who gets snow.  To me it is becoming obvious that the GFS is realizing it cannot drive a system north into the arctic air that  easy.  This happens a lot on the GFS and should not allow the GFS to come further north with this system.  And it shows us a snow event is becoming likely for portions of the Northern Middle Atlantic to the Northeast.  How much snow? Too early to tell  but could be significant.  

The arctic s/w comes into play here because if it speeds up it will keep our system from coming north and keep it on an eastward heading.  This would put areas slightly further south in an extended period of snow from overrunning with some coastal enhancement.  This is possible because we explain the pattern does not support a big ridge in the Pacific into W Canada/Alaska.  The end result would be a faster arctic jet.  

PREVIOUS BLOG ON WHY PATTERN IS SUPPORTIVE

12z GFS Ensembles:

Most of the general comments above are directed toward the Northeast.  But the key here is ensembles are beginning to come around to the eastward adjustment, but still have quite a few against it.  

European

Big upper level low NE of HI (#2) pumps up the ridge (#3) and slows down the arctic s/w (#4).  The end result is a warmer solution with a northward track of the low resulting in a rainy solution for many.  The Euro has a phase 8 look to it in terms of forcing from the MJO which is reasonable, but all ensembles suggest a quick increase into phase 1.  Either way both phases do not favor an amplification of a ridge as far north as the Euro and GFS have currently.

The phasing of the #2 and #1 in the following frame is tough to believe since both features do not support phasing.  The bowling bowl vortex and fast PAC jet.  So it is clear euro is having some problems also.

Conclusion

-Threat is increasing for snow event in Northern Middle Atlantic/Northeast

-Still have a lot of tracking to go!

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