Just wanted to let everyone know the current thinking so I put together my first call map.  A final call map will be posted tomorrow early afternoon.  Reasoning for this only be a first call is because of the current observations showing the potential for a more northwest shift increasing snowfall amounts farther north and west.  With only some ensemble members hinting at this and some mesoscale data it would not be wise to put this in the snow map until we get a better idea of the interaction between the southern stream s/w and northern stream.  

With that said this event is going to based off two main things:

1) Snow to liquid ratios- The snow to liquid ratio is going to be poor across much of Virginia and North Carolina, but a tremendous amount of banding and moisture will make up for this and still put down heavy snows.  As we head to the north across DC/MD/DE/S NJ the ratios improve dramatically.  At first ratios will be close to 5-7:1 but towards the core the dendritic growth layer extends to almost 150mb!! with most of the column below -10C until close to the sfc.  This will result in 12-13:1 ratios.

2) Banding- Frontogenetic forcing will be strong and with the deformation zone I have been highlighting this will only enhance it even more.  One thing I am not seeing in soundings is instability enough to lead to thundersnow or any tremendous bands that produce over 2"hr.  Some SREF members hint at some possible across Southern VA but overall I think we will see banding follow the 700mb frontogenesis and allow a widespread heavy snow band.