Pretty interesting AFD from Mt Holly-
Forecast models continue to forecast cyclogensis occurring beginning
Saturday off the southeast coast with rapidly deepening low pressure
depicted to then move north and east Saturday night through Sunday.
This will occur due to a potent upper level disturbance pivoting
around the base of the long wave trough over the east interacting
with the strong baroclinic zone along the coast.
In terms of impacts to our forecast area, this hinges on the
exact track the storm takes which still remains uncertain at
this time. Generally speaking, the latest 12z deterministic
guidance has our forecast area near the N/W fringe of the
storm`s precip shield. The GFS has shifted slightly farther S/E
with the storm track and precip shield compared to the 0z run
while the ECMWF has shifted a bit west. There also continues to
be spread among the ensembles. One thing that`s interesting to
note though is that the RGEM (the Canadian model) appears to be
supporting a track near or a bit west of the model consensus
based on its placement of upper level features at the end of
its run at 84 hours out (7PM Saturday evening). This model
generally does very well with these types of large scale winter
systems.
Potential storm impacts include not just heavy precipitation but
also strong winds and coastal flooding as the storm will have a
tight pressure gradient with a very strong wind field. Timing wise,
the earliest this would arrive is late day Saturday with the brunt
of the storm occuring Saturday night into Sunday if we get it. Given
the very cold temperatures in place both at the surface and aloft,
all snow is strongly favored in terms of precip type.
The latest NBM probabilistic data has trended back up a bit. For
snow amounts greater than 2 inches (plowable), the range is from
around 60-70 percent near the coast to 40-50 percent near the I-95
corridor with lower probabilities N/W of the urban corridor. For 6+
inches, these probs are around 30-40 percent near I-95 up to 50-60
percent near the coast.