Forecast for February 16th-17th 2013 Storm
I have made a few minor changes to my forecast map which you can see. I have expanded area B, the 1-3 inch area back to the southwest to include much of upstate SC and also a bit further west in NC. I have also reduced the amount of snow to 2-4 inches in area C.
In general the storm is unfolding as outlined yesterday afternoon. The model guidance has for the most part converged on a general precipitation forecast. There appears to be two potential QPF maximum one in the NE piedmont of NC towards the northern coastal plain and SE Virginia. Another is over upstate SC. It is a complicated scenario with several pieces of energy but in general the strong trough is going to go negatively titled today across the Southeast this will produce two general areas of lift one directly associated with the trough dynamics over upstate SC and the other with the coastal low being spawned by this trough off the NC coast. As the evening wears on this energy will coalesce into the one coastal low. This adds to the uncertainty a bit, as there could be a relative precip minimum between the two areas of enhanced lift somewhere across NC, with the best chance being the Sandhills or SE piedmont. But any chance could put that area in a better lift zone.
Because of these complications, the general forecast of snow is tricky, and I readily admit some areas will likely bust. Another complicator is the unusual atmospheric setup. The atmosphere will be very cold aloft with temperatures below freezing from 950-975mb and up in man locations, but at the surface temperatures will likely not cool below freezing during this event. The primary reason is the lack of a cold surface high to our north to drain low level cold air at the surface and the fact that we do not have an antecedent cold air mass in place before the storm begins. Therefore cooling at the surface will come from latent cooling of snow flakes melting just off the surface and also cool air being dragged down from aloft via precipitation. Therefore it may snow in areas with temperatures in the 36-38 range. Accumulating snow will likely fall with temperatures in the 32-34 range where rates are high enough.
The area from upstate SC to the SC midlands to the eastern piedmont of NC and into NE NC/SE Va are the areas to watch for the best QPF and potentially the best snow totals. I will follow all day and update via twitter @RaleighWx.