It seems over the last few weeks we have talked a lot about severe weather in the Carolinas. That threat has established itself once again.
The Setup: A high pressure is set up to the northeast of the Carolinas. This will allow for cool air to flow into the Carolinas. This is what we call Cold Air Damming, or has you have heard here on Carolina Weather Group "The Carolina Wedge".
The Appalachian Mountains play a huge part in the wedge. Cold air is dense, and sinks to the ground. As that air continues to get pushed from the Easterly winds it gets trapped against the mountains, which range in height between 3 and 6 thousand feet. The air can't go over the mountains. The cold, cool air sits and just pools up. This gives cloudy skies for many folks in the Carolinas. When this happens, you will normally see light rain break out along a line from Asheville to Wilkesboro.
This afternoon, evening and overnight, we expect this wedge to break down because a warm front will move through and provide a southerly air flow. That southerly flow will bring in more moisture, and warmer temperatures. It will also set up some instability for thunderstorms. Models indicate that surface based CAPE (Convective Available Potential Energy) or thunderstorm fuel will be high enough to support a few severe storms in Western North Carolina and The Upstate of South Carolina.
Anytime we see a wedge breakdown, our Doppler ears perk up! When you see am influx of warm air - along with a change in the air flow's direction, there is always a severe weather concern.
The Storm Prediction Center in Norman, Oklahoma has parts of North Carolina and South Carolina in a slight risk of severe weather (Level 2 out of 5). This risk runs from the North Carolina / Tennessee line to the US Highway 321 corridor. The entire Upstate of South Carolina falls under the slight category as well. The marginal risk of severe weather (level 1 out of 5) runs from Statesville, NC to Greensboro, NC. All of South Carolina outside of the Upstate is in a marginal risk as well. Damaging winds would be the main concern, but a few storms could produce some large hail. Tornado threat is very low, but not quite zero.