SPC AC 142011

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0311 PM CDT Sat Apr 14 2018

   Valid 142000Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTHEAST LA...SOUTHEAST MS...SOUTHERN AL...AND WESTERN FL
   PANHANDLE...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK AREA IN THE CENTRAL GULF COAST STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK AREA TO EASTERN TN...

   ...SUMMARY...
   Scattered damaging winds and short-lived tornadoes are expected from
   the central Gulf Coast to the Tennessee Valley, mainly through this
   evening.

   Given ongoing eastward advancement of the QLCS in AL, the western
   portions of the categorical and severe probabilities have been
   trimmed.  Meanwhile, the Enhanced risk has been expanded east to
   include more of southern AL and the western FL Panhandle for the
   potential of storms to increase in intensity across far southeast
   LA/MS and spread across southern AL and the adjacent FL Panhandle. 
   The environment across this region of the Gulf Coast will remain
   moderately unstable and strongly sheared ahead of a shortwave trough
   expected to track from the northwest Gulf of Mexico and across the
   Enhanced risk into this evening and overnight.  This ascent will be
   enhanced later tonight as the larger-scale shortwave trough on TX
   emerges east taking on a negative tilt.  

   The ongoing band of storms south of LA appears to be associated with
   the arrival of this aforementioned forcing for ascent.  The expected
   CAPE/shear parameter space will favor damaging winds and a tornado
   threat, as shear values support rotating updrafts embedded within
   the line of storms, and with any preceding discrete cells.

   Otherwise, the northern extent of the ongoing QLCS will continue to
   advance east into a less unstable air mass resulting in a
   diminishing trend of the overall severe weather threat.

   ..Peters.. 04/14/2018

   .PREV DISCUSSION... /ISSUED 1116 AM CDT Sat Apr 14 2018/

   A well-organized squall line with embedded bow/lewp structures
   continues to progress eastward across parts of MS/LA into AL.  A
   combination of dewpoints in the mid/upper 60s and at least broken
   sunshine will maintain MLCAPE values around 1000 J/kg ahead of the
   line through most of the day.  Local VAD hodographs and forecast
   sounding data suggest strong low-level shear is present and will
   persist across AL, maintaining the potential for rotating updrafts
   and a few tornadoes.  Some potential exists for isolated cells ahead
   of the main line, which could result in an isolated tornado/wind
   threat.  However, present indications are that the squall line is
   the primary severe threat.

   This evening, the convective line will continue tracking eastward
   into eastern AL where a more dry/stable low-level air mass is
   expected to result in slow weakening.  Farther south, the storms
   will maintain some intensity across the FL Panhandle.  Sufficient
   instability/shear suggests that the risk of at least isolated
   damaging wind gusts and/or tornadoes will persist through much of
   the night.

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