January 17th-18th Snow Event
Good morning folks, things look on track for our current winter storm and I have no major changes to the forecast from yesterday. I did update the snowfall forecast graphic slightly mostly beefing up amounts a bit.
General Discussion
It is currently snowing in central Mississippi where reports so far have come in around a dusting to 1 inch. As far as the rest of today goes, look for the area of rain over east TN, Georgia, and the Carolinas to strengthen and form the classic V-shape by this afternoon with moderate to heavy rain falling within it. The area of precipitation over Mississippi, associated with the upper low, will merge with this band of rain to create the classic comma-head look on satellite and radar by late this afternoon and evening across northern Georgia, NE AL, east TN, and western NC. This comma-head, which will represent the deformation band of this quick-hitting storm, will be where the strongest vertical velocities lie and where a band of heavy snow will form and move east. Model soundings show steep mid-level lapse rates and strong vertical motion, enhanced by the placement of the region in the right rear entrance region of a strong jet streak, and this could lead to some thunder and lightning, especially as the changeover is occurring. It appears that for most areas outside the mountains of northern NC, NE TN, and western Virginia, this will be a 3-6 hour period of snow.
I think an area of a dusting to 2 inches of snow will move into northern Alabama, and NW and N Georgia this afternoon and evening. The latest model soundings I have looked don’t look to promising for snow in the Atlanta metro area. It appears that the boundary layer may not cool enough to allow the snow to reach the surface this evening. They could see some flakes but even a dusting seems a stretch although it is possible. However areas just NW of the city will likely see some snow and perhaps some minor accumulations.
The highest snow totals as of now look to be in NE TN, NW NC, western and southwestern Va, and extreme southern WV. The reason is that this will be the area with the longest period of snow even though many will likely start as rain also. This area could see 6-12 inches of snow, particularly in the higher elevations. Cities in this area include Bristol, TN and Boone, NC. I do have concerns about areas of NW NC, in the escarpment. There will be a limited time of NE winds, with the winds shifting to the N and NW quickly and the high resolution NAM as well as our in-house high resolution models show local snow minimums in this area. This will result in downsloping and potential minimums of snowfall in areas from say Morganton to Lenoir to Wilkesboro. This is a tricky forecast though and will need to be monitored via radar and surface winds. Again this is not your typical winter storm with a gulf low moving NE out of the gulf with winds with a prolonged easterly component, so accumulation tendencies will also likely be atypical.
As the deformation bands moves across areas of Virginia/NC east of the mountains, look for a 3-6 hour period of moderate to heavy snow with a rapid changeover from rain to snow and again the possibility of some thunder and lightning. Snowfall rates could approach 1-2 inches per hour with this band and obviously if you can achieve that for a couple of hours, snow will accumulate quickly. The area east of the mountains with the best potential to overachieve is likely from the NW/N piedmont (Triad) into east-central Virginia (near Richmond). High-resolution modeling shows the potential for a vigorous snow band to set up there and hence I have upped the totals there to 3-6 inches. Further east and south, amounts taper off but 2-4 inches seem likely for the Triangle and for much of the NE piedmont of NC into the northern coastal plain and SE Virginia, with lesser amounts as we see a sharp gradient across southern NC. Charlotte will be an interesting place as northern Mecklenburg County could see several inches and southern Mecklenburg a dusting to inch. In general Charlotte and upstate SC will sweating bullets as I could see this being a shutout or a few inches, they are probably the trickiest area along with the escarpment areas to forecast for right now.
I will be following this storm all day obviously, and will post updates on twitter @RaleighWx and on the http://americanwx.com bulletin board. I will post an update this evening on how things are unfolding, but for now, I will probably just make this current forecast map my final call, since we are getting late in the game, unless the 12z data comes in dramatically different.
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