Louisiana Severe Weather Threat Thursday 12/31

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...Southeast Texas/Lower Mississippi Valley/Central Gulf Coast States...

An upper-level low will move from northern Mexico into the southern Plains on Thursday. Divergent flow aloft will overspread eastern Texas and Louisiana as the negatively-tilted system deepens. A large cluster of thunderstorms appears likely to be ongoing in southeast Texas at the start of the period. This convection is forecast to move eastward as a low deepens and moves northeastward into the ArkLaTex. Although instability will be weak along the attendant surface trough, strong deep-layer shear will create conditions favorable for severe storms. Lift associated with a mid-level jet, rounding the base of the upper-level system, will provide additional support for organized storms. As the mid-level jet moves eastward across the Lower Mississippi Valley on Thursday, thunderstorm development is expected to occur across parts of Louisiana and Mississippi.

Instability is forecast to gradually increase across the moist sector, which should be located from Louisiana to southwestern Alabama. Discrete thunderstorms that develop ahead of the cold front across the moist sector could have a wind damage and tornado potential. During the late afternoon, the most favorable area would be in far southeast Louisiana, where the models maximize instability at the northern end of the moist axis. The corridor of maximized low-level moisture is forecast to shift eastward across southern Mississippi and southern Alabama during the evening and overnight period. Models suggest the possibility of a convective line located along the moist axis. This line would be associated with a continued wind damage and tornado threat during the overnight period.

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