SPC AC 290700

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CST Thu Nov 29 2018

   Valid 301200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE ARKLATEX REGION FRIDAY EVENING AND OVERNIGHT...

   ...SUMMARY...
   Severe storms posing a threat for damaging wind, hail and a few
   tornadoes are possible Friday afternoon into the overnight from a
   portion of the southern Plains into the lower Mississippi Valley
   region.

   ...Synopsis...

   Shortwave trough currently approaching the CA coast is forecast to
   amplify over the southwest U.S. today (Thursday) before continuing
   east and ejecting negatively tilted through the southern Plains and
   lower MS Valley Friday evening and night. Surface low should deepen
   along the KS/OK border within left exit region of strong (100+ kt)
   upper jet before moving into eastern KS overnight. By early evening
   the warm front should extend eastward from the low through northern
   OK and northern AR, with a cold front extending southward through
   central OK into north central and southwest TX.

   ...Northeast Texas, eastern Oklahoma, Arkansas and extreme northern
   Louisiana...

   Partially modified Gulf air with low to mid 60s F dewpoints as far
   north as the Arklatex region will advect through the pre-frontal
   warm sector along a strengthening southerly low level jet. This
   destabilization process will be tempered somewhat by widespread
   clouds which will limit surface heating, likely resulting in weak
   low-level lapse rates and possibly maintenance of a very shallow
   near-surface stable layer. Nevertheless, a corridor of up to 1000
   J/kg MLCAPE may evolve across the Arklatex region as deeper ascent
   and cooler temperatures aloft within the upper jet exit region
   overtake the western portion of the moistening warm sector.
   Thunderstorms should develop and gradually increase in intensity
   from northeast TX into eastern OK within zone of destabilization and
   increasing deep ascent. Strengthening wind profiles with 50+ kt
   effective bulk shear will promote organized storms including
   supercells. While low-level hodographs will be sufficiently large
   for low-level mesocyclones and a few tornadoes, tendency will be for
   low-level winds to gradually veer within western portion of the warm
   sector where the more robust destabilization is expected.
   Given the steepening mid-level lapse rates along and north of the
   upper jet axis, the thermodynamic environment may also support large
   hail within the more robust updrafts. Activity will spread east
   through the lower MS Valley region with a continuing severe threat
   overnight.

   ...Southern Louisiana through southern Mississippi...

   Southern-stream shortwave trough over northern Mexico is forecast to
   weaken as it accelerates through the northern Gulf. Showers and
   thunderstorms associated with this system will likely move away from
   the western Gulf early in the period and thus may not have a
   significant impact on quality of moisture return through LA. A
   separate area of showers and thunderstorms should develop across LA
   into MS later Friday afternoon into the overnight within zone of
   low-level confluence and destabilization resulting from advection of
   upper 60s to near 70 F dewpoints inland. Forcing aloft and mid-level
   lapse rates will be weak resulting in somewhat marginal normalized
   CAPE, serving as a potential limiting factor for a more robust
   severe threat. However, wind profiles with large hodographs will
   evolve overnight, which along with expected moist, near-surface
   layer could support a few supercell storms with low-level
   mesocyclones capable of a few tornadoes.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:  10%     - Enhanced
   Wind:     15%     - Slight
   Hail:     30%     - Enhanced

   ..Dial.. 11/29/2018

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