Mesoscale Discussion 2127
NWS Storm Prediction Center Norman OK
0841 PM CDT Wed Oct 30 2019
Areas affected…southeast Louisiana into central Mississippi…west-central Alabama
Concerning…Severe potential…Watch unlikely
Valid 310141Z – 310345Z
Probability of Watch Issuance…20 percent
SUMMARY…Isolated severe storms are possible over the next several hours ahead of a cold front. Strong wind gusts or a brief/weak tornado cannot be ruled out.
DISCUSSION…A cold front continues to develop into western LA and AR, with a quasi-stationary front extending from northeast LA across central MS and into northern AL. Ahead of these boundaries, a moist air mass exists with precipitable water values of 2.00-2.20″ over LA and southern MS, and 70s F dewpoints.
Recent convective trends have been increasing over LA and MS, in a zone of increasing warm air advection ahead of the cold front. Here, effective SRH is averaging near 100 m2/s2, with similar values of 0-1 km SRH near the front over central MS.
As the upper trough continues to deepen and height falls overspread the area tonight, shear will increase gradually with 850 mb southwesterlies to 40 kt by 06Z. This will provide a more favorable environment for a few severe storms, the limiting factor being instability. However, the deep moist layer as seen on 00Z soundings and increasing lift (especially as the cold front surges) may counteract marginal thermodynamics to support at least isolated severe storms. Storm trends will continue to be monitored, with watch potential hinging mainly on severe coverage.
Central Alabama Weather 