SEVERE WEATHER THREAT FOR GUKF COAST STATES OCT 31, 2018

SPC AC 311956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Wed Oct 31 2018

   Valid 312000Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   TEXAS TO SOUTHWEST MISSISSIPPI...

   ...SUMMARY...
   The greatest risk for severe thunderstorms, capable of producing
   damaging winds, hail, and tornadoes, exists from southeast Texas to
   the lower Mississippi Valley through tonight.

   ...Discussion...
   Have removed severe probabilities from portions of the Big Country
   into north Texas, where the south/southeastward progression of a
   cold front and an expansive trailing precipitation shield are likely
   minimizing any severe threat. Additionally, Marginal probabilities
   have been extended westward towards El Paso, where forcing for
   ascent with the primary shortwave impulse may continue to support a
   localized hail/wind threat.

   Otherwise, a greater tornado/damaging wind potential is still
   expected to materialize late this evening into tonight from
   southeast Texas to the lower Mississippi Valley, and no changes have
   been made to the ongoing probabilities here. For more information on
   this threat, see the previous discussion below.

   ..Picca.. 10/31/2018

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Wed Oct 31 2018/

   ...TX today to LA/MS overnight...
   A midlevel shortwave trough now near El Paso will continue eastward
   across TX through tonight.  Weak cyclogenesis is expected by this
   evening and continuing through tonight, along a pre-existing front
   from central TX to the Mid South.  A moist low-level air mass is
   already present south of the front, with low 70s boundary-layer
   dewpoints spreading across the northwest Gulf coast.  Gradual mass
   response to the cyclogenesis will result in strengthening low-level
   flow/shear, especially tonight across LA/MS.

   Ongoing convection in TX has largely remained elevated atop the
   frontal surface, but may gradually transition to surface-based
   storms along the front later this afternoon.  Isolated strong-severe
   storms will also be possible this afternoon/evening into southwest
   TX, along the west edge of the richer low-level moisture and in the
   zone of stronger low-midlevel ascent preceding the shortwave trough.
   Farther east, the ongoing warm sector convection across the upper TX
   coast should persist through the afternoon and spread slowly
   eastward/northeastward.  Additional warm sector storm development is
   also expected tonight along the moist axis into southern LA.

   Wind profiles are only marginally favorable for organized/supercell
   storms at present across TX, with slow strengthening of vertical
   shear expected later this afternoon through tonight farther east
   toward the lower MS Valley.  A few supercells could evolve from the
   ongoing upper TX coast convection, as well as embedded
   supercells/bowing segments along the front from central into east
   TX.  This frontal convection will likely evolve into a line that
   will move eastward overnight, with an accompanying threat for
   damaging winds and a couple of tornadoes with embedded circulations.
   The more substantial supercell/tornado threat is expected overnight
   into parts of LA (and possibly MS) within the moist sector, and
   where low-level shear becomes the strongest.  A strong tornado or
   two will be possible, especially with any pre-frontal supercell
   clusters, where effective SRH increases to greater than 400 m2/s2 in
   a moist environment with sufficient surface-based buoyancy.

Tornado Outlook 

 Strong Wind Outlook

 Hail Outlook

 Severe Thunderstorm Outlook