6PM Day 1 Convective Outlook for Sunday, February 15. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN TEXAS ACROSS LOUISIANA AND INTO SOUTHERN MISSISSIPPI
SUMMARY
Severe thunderstorms remain possible this evening and overnight from eastern Texas across the Lower Mississippi Valley. A few tornadoes along with scattered damaging winds will be possible.
Sabine into the Lower Mississippi Valley
A fast-moving shortwave trough will move from TX toward the lower MS Valley through Sunday morning, providing lift and cooling aloft. At the surface, low pressure will move from the ArkLaTex area into northern MS, with a cold front trailing southwest from the low.
Ahead of the cold front, the air mass will continue to moisten as a warm front lifts northward across southern LA and eventually southern MS and AL late. Behind the warm front, dewpoints will likely rise into the mid 60s F, aided by veering low-level winds and 40-50 kt at 850 mb.
The combination of increasing low-level shear will likely result in effective SRH values over 200 m2/s2, perhaps near 300 m2/s2 where non-zero low-level buoyancy exists. Given the rapid progression of the upper trough, a squall line is likely to be maintained overnight, possibly reaching southwest AL by 12Z. Both damaging winds and a few embedded/QLCS tornadoes will be possible as this line interacts with the increasingly moist air mass. The main mitigating factor to overall magnitude of severe will be the instability values, with MLCAPE averaging 500-750 J/kg overnight.
For more information see mesoscale discussions #0078 and #0079.