Tracking the Trough...
I don't know what it is about recent Winter storms but they just seem be more and more difficult to forecast. This one is a bear...forecasting a Norlun trough is almost like forecasting where a squall line will form...very, very difficult. Of course this isn't your typical Norlun trough either...there may actually be more than one intense band that sets up or a band that travels a pretty long distance up the coast with multiple flare ups...fun stuff!
I like where the NAM is placing the Norlun to set-up and start...based on the upper level vortex...700mb lift and 850mb overrunning inflow...it has it focused to our south and west NYC area looks to be ground zero. I also think that we will break into light snow by afternoon on Friday based on onshore moisture enhanced flow being lifted by a little 500mb lift and upper level divergence but the main band of heavy snow should stay to our south all Friday and deep into the evening. After that it gets more complicated...does the trough migrate north? Does a new one form to our north...over us? Does a new surface low spin up on the original Norlun trough in our coastal waters? There is definitely bigger snow potential early Saturday morning as the energy from the Norlun to our south starts to migrate north. There is also bigger snow potential late Saturday when the upper level vortex traverses the Northeast. Pinpointing these zones of heavier snow will also be very tough and could end up just north and just south of the Boston Metro area. Clearly, very complicated and honestly with all these vortices and the upper level cut-off floating through any and all scenarios are entirely possible. With that said at the very least we are talking about a few inches of snow with potential for 6 or more inches.
