SPC Mesoscale Discussion: Severe Potential… Watch Likely

SUMMARY…Thunderstorms are expected to develop by 17-18Z over a large part of the Southeast U.S. and increase in coverage and intensity during the afternoon, posing a risk for damaging wind and hail. A WW will probably be needed for a portion of this region by 17Z.

DISCUSSION…A moist warm sector resides over a large part of the southeast U.S. with dewpoints around 70F and temperatures climbing through the mid 80s F as of 16Z. Latest objective analysis indicate MLCAPE around 1500-2000 J/kg and further destabilization will occur as the surface layer continues to warm. Water vapor imagery shows a progressive shortwave trough moving through the TN Valley, with an MCV also indicated over southeast TN/northern GA. A low-level confluence zone is forecast to evolve well inland from the coast from southern AL through southern GA. The combination of forcing for ascent associated with the MCV and progressive shortwave trough, surface layer destabilization and subtle boundaries, should promote warm sector initiation by early afternoon. While deep-layer wind profiles are unidirectional west southwesterly with small 0-1 km hodographs, a belt of 50 kt mid-level winds within the base of the trough is resulting in 30-35 kt effective bulk shear. This environment should support both multicell and some supercell structures with discrete modes eventually evolving into lines and clusters capable of damaging wind and hail.

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