CHARLOTTE, NC (WBTV) – An upper level system and surface cold front will move across the Carolinas on Wednesday, bringing with it the possibility of severe weather.
The Storm Prediction Center has placed most of the area, including Charlotte, under a "Slight Risk" category for severe storms that could fire up on Wednesday afternoon. The SPC has focused its concern on the Piedmont, where they expect a line of storms to move through late in the day.
There are several reasons we're watching this system. First is the timing of the cold front's passage. At this time models have the front moving through in the late afternoon or early evening hours of Wednesday, a time of day when conditions are usually more suitable to severe weather. Also, with Southwesterly winds in the lower levels of the atmosphere forecast for Tuesday, plenty of Gulf moisture will be in place before the front arrives.
In addition to moisture, forecasters also look for instability in the atmosphere. Wednesday's forecast has plenty. On a plot of upper level conditions, forecasters can tell how buoyant a parcel of air would be if it were somehow forced upward. If we take a warm air parcel and move it upward in the atmosphere, it will continue to rise as long as it remains warmer than the air around it. All that warm air needs is some sort of trigger to get it rising initially. Our next cold front will serve as that trigger. If the front were to move through a buoyant area, we could see rapidly rising air that could form very tall thunderstorms, which have the potential to become strong to severe.
The good news with this next system is that the environment will be very unfavorable for tornado development. Tornadoes need lots of wind shear, or a change in wind direction as you climb higher in the atmosphere. Instead, winds throughout the atmosphere will be largely unidirectional, meaning that a line of storms along the front is likely.
Severe storms can still form along these lines, and damaging winds will still be possible and can be just as dangerous as tornadoes.