IMPENDING SEVERE WEATHER WATCH FOR PORTION OF THE MID SOUTH

 Mesoscale Discussion 0144
   NWS Storm Prediction Center Norman OK
   0559 AM CST Tue Feb 07 2017

   Areas affected...Central and southeastern Louisiana...much of
   southern Mississippi...far southwest Alabama

   Concerning...Severe potential...Watch likely 

   Valid 071159Z - 071400Z

   Probability of Watch Issuance...80 percent

   SUMMARY...The threat for severe thunderstorms should increase
   through the day. Very large damaging hail is possible over Louisiana
   into southern Mississippi, with isolated tornadoes as well. The
   threat will develop from west to east, affecting Alabama later in
   the day.

   DISCUSSION...Very cold air aloft will continue to spread eastward
   across the region today with upper trough axis near the Mississippi
   river by 18Z. At the surface, substantial low-level moisture is
   already in place from Texas into Louisiana, with mid 60s dewpoints.
   This has created an unstable environment with MUCAPE in the
   1500-2000 J/kg range. A more stable air mass currently resides
   roughly half way across Mississippi and points east, but gradual
   destabilization is expected there as well.

   Low-level winds will remain veering with height, with 0-3 km SRH on
   the order of 200-300 m2/s2 throughout the day. Winds around 850 mb
   will tend to veer as the upper trough approaches, but at the same
   time, intense upper-level flow will spread southeastward across
   Louisiana into southern Mississippi, lengthening hodographs aloft
   and resulting in an increasingly favorable environment for very
   large hail. While tornadoes may not be the primary threat, a few
   will be possible due to supercell storm mode and sufficient
   low-level shear. 

   The greatest severe risk overall is likely to exist from Louisiana
   into southern Mississippi in closer proximity to the more unstable
   air, which is not forecast to spread east very quickly.

   ..Jewell/Guyer.. 02/07/2017