A strong upper level low will push though the Southeast on Tuesday, creating for an extremely difficult forecast. Small details in the upper atmosphere will equate to large changes regarding precipitation type that falls at the surface. I am growing increasingly more confident that at least the immediate Foothills or WNC right up next to the Blue Ridge Mountains will see snow fall Tuesday morning. Both the NAM & High Resolution NAM show this. The High Resolution NAM though blossoms the precipitation earlier, and therefore more hits the SW mountains of WNC. The 3km High Resolution NAM even shows snow falling around Asheville. We are beginning to see a Northwest trend on all models, but it remains to be seen how far Northwest the models move the precipitation shield. Below you can see the most recent model trends.
Upper Level Low
The upper level low pressure that will push into the area is what is creating havoc with this forecast. An upper level low will control the direction of motion with precipitation as its lifted into the atmosphere, and has the ability to make its own cold air through dynamic cooling. When the upper level low begins to go negative tilt, precipitation can rotation around the upper level low, where it falls in a cold sector. Many times this precipitation falls as snow, grapel, or hail. Below you can see how the 3km NAM and the high resolution NAM crank back the upper level low towards WNC as it rotates through. I believe that any precipitation that falls, has the chance to be frozen.
These appear to be very similar, but their precipitation depictions are somewhat different. Below you can see the 12z NAM 12km radar depiction, and it shows the setup a bit more elongated, and affects the Foothills and even Charlotte more. This would indicate a stronger Lee side development of the captured surface low thats developing and forming its precipitation band along a zone of truncation. Wherever this strong band develops, it will likely snow. It could be across Upstate SC, or WNC, or the Foothills of NC, or even the Piedmont of NC. There is not enough data to nail it down just yet, but check back soon.. ill have another detailed update together before the storm approaches.