Taking a look at the current surface charts over the CONUS, you can see the Arctic HP system slowly building into the plains and eventually the Ohio Valley. This will setup a strong cold air damming situation, even as the HP slides offshore, it will be reinforced on the backside of strengthening surface low pressure.
As of now I am favoring the ECMWF, as it was the first model to catch onto the phasing in this split-flow pattern. The NAM is generally unreliable outside of 36 to 48 hours and has a tendency to produce large errors in QPF fields past this range due the high-res model physics. The GGEM has performed well also, but for the time being I am not really factoring it into this forecast.
I am currently favoring a SLP track similar to the analogs at the bottom of this article. The evolution is not unlike other large storms of the past. A s/w will ride through the southern CONUS and be caught by a polar jet wave entering the US over the northern plains. These two features will phase and induce a strengthening low pressure over the northern gulf, which will track just offshore the east coast as the trough tilts negatively. This will send a large precipitation shield northeast and eventually form a deformation band of snow on the backside. Climatologically, the sfc track I see would be favorable for the western and north-central Carolinas, as well as far NE Georgia snow wise. As you head east of a line from NW Charlotte to Greensboro, snow will mix with sleet and eventually freezing rain as warm air aloft is drawn in from the coastal low(east wind). A thin zone of freezing rain is also likely east and southeast of this transition area. This zone is where the most impact will likely be felt by this storm. Ice accretions up to an inch are possible, as well as a few inches of sleet and snow. This would cause severe tree and power line damage.
There are several situations to monitor that will impact the eventualities of this storm. The first would be convective banding near the SLP over the northern gulf Wednesday. As the SLP begins to organize, history has shown us that convective banding can rob moisture advection to the northwest of the SLP. Some models, especially the GFS, have hinted at this a few times. Another feature is the progressive nature of the polar s/w that is entering the United States. This s/w is not riding down a large North American ridge, therefore the margin error may be on the more progressive side of the coin(meaning a later phase and track east of where I anticipating). Surface temperatures may also continue to trend a bit colder leading up to the storm, as the models realize the low level nature of the cold air.
Analogs – 12/25/10, 1/22/87
Forecasted totals are based on a blend of analogs, expected slp track, climo, model soundings, and the ECMWF/ECMWF ENS. I will issue another update tomorrow night.