I'm keeping a close eye on a potential snow threat for next weekend (Dec 20th-21st) for the Mid-Atlantic States. At this time the App Mnt's and Piedmont regions have the best chance for mostly snow, while the Coastal Plain regions from VA to DE and NJ look to be mostly rain, with some snow on the back end of this storm.
Global models all have different solutions in handling this rather complex upper level set up. With this threat still being 6-7 days away, the uncertainty level is high at this point. Split flow patterns with both a PJ and STJ involved can be tricky, but usually produce nice storms when they partially phase or fully phase. Per one of the best Global models and great in these patterns (THE EURO) develops a potential full phase of 2 pieces of energy which occurs near the M/A coast of VA, during next Saturday night into Sunday morning. The system begins to develop over the lower MS Valley during Friday and then moves ENE to the VA coast by Sunday morning.
As this storm is developing a large area of High pressure is pressing Southeastward into the G/L's region. This supplies us with the fresh cold air and suppresses the storm to a more southern track. The last 2 runs of the EURO model suggest a nice snowstorm for much of the M/A States with widespread 6"-12" amounts over the Mnt's and Piedmont of the M/A.
Though this a great model in this range (The EURO) I do think it's overdone with snowfall amounts (See attached Pics) but this has the potential to be a nice storm as the EURO suggests, so we need to consider it just as POTENTIAL for now, with it still being 6-7 days away !
As a PRELIM CALL, I think a 3"-6" event is possible for ROA / LYH / CHO VA areas next weekend. I'll have more towards mid week ! Del Valley areas look to be mostly Rain with some snow on the backside (Accumulations also possible there).