The storm system that is expected to bring snow to the mountains and cold rain to the coastal plain will be affecting the Carolinas within a few hours. My final snow, sleet, and freezing rain forecast has been issued.
The storm is expected to track along the coastline of the Gulf of Mexico before moving northward off the Carolina coast. Moisture overruns North Carolina later this afternoon and tonight. The heaviest snows will fall across western NC between 2:00 a.m. and 12:00 p.m. For central locations, the heaviest precipitation is between 4:00 a.m. and 2:00 p.m. Major accumulations of snow and sleet is expected across western and central NC. Freezing rain is also expected to accumulate in parts of central and eastern NC.
The image loop below is the High Resolution NAM and it shows the overall progression of the storm from Saturday evening through Monday morning.
The greatest issues at the moment deal with the extent of sleet mixing with the snow. As many of you know, warm air aloft will melt the snow and change it to sleet. Models indicate this warm layer of air may move into the central portion of NC, which would keep snow totals lower. Thus, I have kept the snow totals lower in parts of central NC due to sleet mixing in.
Across the Catawba Valley northward into the Triad, the forecast is also complicated. The temperature aloft approaches 32° throughout the storm. If the warm layer of air moves further north than expected, the accumulation of snow and sleet would be on the low end of the scale. If the warm layer of air remains further south, then the accumulation would be on the upper end of the scale, and possibly higher than I expect.
There is relatively good agreement in the models in terms of how much precipitation will move northward into the area. All the major global models show roughly 2 inches of precipitation from I-40 southward. As you move northward, the models show around 1.5 inches of precipitation. This is a lot of moisture for any winter storm in the Carolinas.
My final forecast snow and sleet map shows most areas outside the mountains remaining under one foot of snow from this system. While other models show higher snow totals in the foothills and western piedmont, I am not convinced that the warm layer of air will stay far enough south the prevent areas shaded in yellow from turning into sleet and keeping snow totals lower. In the event the warm layer stays further south towards I-85, then the areas shaded in yellow may see higher snow totals.
For the mountains, I expect this system to remain mostly snow, thus the higher snow totals.
As we move towards I-85 and the Charlotte metro area, this zone is expected to be the battle ground between the warmer air and the colder air. At points, this zone may change to freezing rain or a cold rain. This area may see ice accumulations approaching .5 of an inch, which may cause widespread power outages. The areas shaded in green, light blue, and dark blue is where the transition zone occurs, so these areas are the most difficult part of the forecast. Overall forecast confidence remains relatively low in these areas.
Towards the Raleigh/Durham area, there will be a sharp cut off from major accumulations and little accumulations. That is why Raleigh is right on the cut off line between 1-3 and 2-5 inches. Areas west of Raleigh have the chance to receive more than 5 inches of snow and sleet if the warm nose is remains south.
This is a very serious and dangerous storm system approaching the Carolinas. Please make final plans before the system begins impacting our weather. I will have a video later this evening on Facebook, and I will keep you up to date with the latest information on this system.