SPC AC 200058

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0658 PM CST Tue Feb 19 2019

   Valid 200100Z - 201200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE LOWER MISSISSIPPI VALLEY...

   ...SUMMARY...
   A marginal risk for severe storms will evolve later tonight from
   Louisiana into south central Mississippi with primary risks being a
   couple of strong to damaging wind gusts and perhaps a brief tornado.

   ...Louisiana through south central Mississippi...

   A warm front situated along the LA coast will advance farther inland
   this evening, reaching southern MS later tonight. The deeper forcing
   for ascent resulting from a shortwave trough moving northeastward
   into the southern and central Plains will remain well northwest of
   the warm sector with only weak surface low development expected on
   the warm front. By 12Z Wednesday this low will be situated over
   southwest MS with a cold front trailing south into southwest LA. The
   warm front will extend southeast from the low through southern MS. 

   As the moist, warm sector moves inland, dewpoints will rise to near
   70 F along the LA coast and mid-upper 60s farther north into
   southern MS. Persistent low-mid level ascent and destabilization
   along the warm conveyor belt should promote an increase in
   thunderstorms along and east of the cold front later tonight. 00Z
   RAOB data show a mid-level inversion over southern LA into southern
   MS. Persistent low-mid level ascent may contribute to some cooling
   in the inversion layer, especially well inland from the coast,
   possibly supporting more robust updrafts. However, offsetting this
   will be greater likelihood of only partial erosion of the low-level
   stable layer with northward extent, suggesting most storms could
   remain slightly elevated. Nevertheless...storms developing in this
   regime may become close to surface based, where effective storm
   relative helicity and deep shear will be sufficient for some
   supercell and bowing segments. Given the potential limiting factors
   due primarily to weak low-level lapse rates and presence of at least
   a persistent, modest mid-level inversion, will maintain marginal
   risk this update.

   ..Dial.. 02/20/2019

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