1/1/14: Hard to see with a still picture but take a look at the WV loop. First, the still Water Vapor. You have the obvious active sub tropical jet stream, you have the Polar jet stream.
now…. the loop… You can see the Polar Jet is already started to blend into the Sub jet. Watch the dry slot start to fill in and watch those milky white colors start blending into the subjet. Diving south right into the tropical feeding moisture.
What this is doing is pushing the 500mb level downwards and you can see this too currently. If that goes negative tilted near the coast, snow totals would be enhanced and that’s what the models saw in todays update. It goes slightly negative hence the Blizzard and Winter Storm Warnings with widespread 6-15″ forecasted. Just fascinating stuff from a meteorological perspective..