The overall weather pattern has been very quiet across much of the US, east of the Rocky Mountains here recently. However, the potential is there for severe thunderstorm activity across parts of Dixie Alley. While the Storm Prediction Center has highlighted parts of Arkansas, Louisiana, and Mississippi for Wednesday, the area at risk looks to be larger in size. That could easily include portions of Alabama and Tennessee.
Dewpoints look to not be lacking with this particular setup. Ample amounts of moisture will be in place across Dixie Alley Wednesday afternoon and evening. The surface temperatures Wednesday Afternoon look to be in the lower 70s. When combined with these dewpoint values in the middle 60s, the lifted condesation levels will be low enough that would allow a higher potential of tornado activity.
The winds at the surface (in red), along with winds at 850 mb (5,000 feet) and 500 mb (18,000 feet), do indicate that the wind is forecast to turn with height. When we say turn with height, the wind at the surface is forecast to be south to southeast. At 850 mb and 500 mb, the wind direction is mainly from the west and southwest. That will allow any thunderstorm that does develop to have potential to rotate. In addition, CAPE values in excess of 500 J/Kg are widespread across the region.
No shortage on the amount of shear in the lowest one and six kilometers is noted on tonight’s run of the North American Model (NAM). In the lowest one kilometer, 25 to 30 knots of shear are noted. In the lowest six kilometers, shear amounts in excess of 40 knots is noted. These values are more than sufficient for supercell thunderstorm activity to development.
Also, there is no shortage on the amounts of helicity in the lowest one and three kilometers. In the lowest one kilometer, helicity values in excess of 200 units are noted especially across northern Mississippi and northern Alabama. Three kilometer helicity amounts in excess of three hundred units are noted across the same region. That will allow tornado potential to increase with any thunderstorm activity that does develop.
When we combine all the data above, it is easy for one to see that the Supercell Composite and the Significant Tornado Parameter are getting up there in value. Supercell values higher than 4 are noted across much of the region Wednesday afternoon. That would bring about the chance for sustained supercell thunderstorms. The significant tornado parameter values are higher than one unit across Dixie Alley as well on Wednesday afternoon. These areas would be at an increased risk for tornado activity.
Overall, the potential is on the board for severe thunderstorm activity across Dixie Alley Wednesday Afternoon and Wednesday Night. We will continue to monitor the situation for you. Stay tuned.