Mesoscale Discussion 334 — Severe Threat Continues Across North Alabama

SUMMARY… An organized line of thunderstorms may pose a continuing risk for damaging wind gusts another couple of hours, but this threat probably will diminish across the Cumberland Plateau by 2-3 AM EDT. A new severe weather watch currently seems unlikely, but trends will continue to be monitored.

DISCUSSION… A well organized convective system continues to evolve to the east and south of the mesoscale convective vortex, preceded by a notable meso low migrating northeastward near/northwest through north of Nashville vicinity. Richer boundary-layer moisture characterized by 60s F+ dewpoints is becoming cut off near the southern Tennessee border, which model forecast soundings indicate will minimize destabilization northeastward across middle Tennessee toward the Cumberland Plateau. However, 70s F+ surface temperatures have been maintained in a plume wrapping into the center of the meso low.

Given the strength of the west-southwesterly lower/mid-tropospheric wind fields (40-70+ kt in the 850-700 mb layer) impinging on the rear of the convective system, the low-level thermodynamic profiles with warm and unsaturated layers may support a continuing risk for downward mixing of potentially damaging gusts to the surface. This probably will persist at least another hour or two, but may begin to diminish as forcing for ascent spreads into the Cumberland Plateau toward 06-07Z, where the boundary layer remains cooler and warm advection may not contribute to appreciable warming.

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