Apr 14, 2019 1300 UTC Day 1 Convective Outlook

Day 1 Convective Outlook  

   NWS Storm Prediction Center Norman OK
   0752 AM CDT Sun Apr 14 2019

   Valid 141300Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE
   WESTERN CAROLINAS TO PORTIONS OF PENNSYLVANIA AND OHIO...

   ...SUMMARY...
   Severe thunderstorms are forecast today in parts of the Ohio Valley
   southward through the southern Appalachians and northeast Gulf
   Coast. Severe thunderstorms are possible this evening/tonight east
   of the Appalachians from the Carolina Piedmont northward into parts
   of the Mid-Atlantic states.

   ...Synopsis...
   In mid/upper levels, a synoptic-scale trough is evident in moisture-
   channel imagery from MN/IA across the Ozarks and southwestward over
   south TX, with embedded vorticity max and remnant low over the
   western Ozarks region.  This trough will move east-northeastward to
   a 00Z position from Upper MI to the IL/IN border, western TN, MS,
   and southeastern LA.  By 12Z the trough should lost amplitude, but
   still remain large and well-defined, from southern ON to WV, the
   Carolinas, and southern/eastern GA.

   At the surface, 11Z analysis showed an elongated surface cyclone in
   the PAH-MEM corridor.  A more-coherent low is forecast to
   consolidate through midday then move northeastward to near the CLE/
   CAK area by 00Z, then over or very near VT by 12Z.  The associated
   leading cold front was drawn from the low across northern/
   southwestern AL and south of southeastern LA over the Gulf.  A
   secondary/reinforcing cold front extended southwestward over AR.  By
   00Z, the main front should reach eastern OH, WV, the western
   Carolinas, and central/southern GA.  By 12Z, the front is forecast
   over the southeastern NY/NJ area, then over Atlantic waters to south
   FL.  A warm front, drawn initially in wavy fashion over eastern TN
   and western/northern NC -- will shift northward erratically through
   the afternoon, catching up to a synoptic boundary initially
   extending from the low east-northeastward across northern portions
   of KY/WV/MD.  The combined warm front then should move northward
   through much of the Mid-Atlantic region.

   ...Upper Ohio Valley, Mid-Atlantic to southeastern CONUS...
   Scattered thunderstorms are expected to move from southwest to
   northeast across the outlook area through this evening, offering a
   primary threat of damaging to severe gusts, but with a few tornadoes
   also possible.

   A broken, messy band of precip and embedded thunderstorms is ongoing
   ahead of the front from portions of southeastern TN across the
   western FL Panhandle, with at least isolated severe potential
   remaining in a low-CAPE/high-shear setting.  Refer to the remaining
   portions of watches 57-59, and accompanying mesoscale discussions,
   for more on the near-term scenario.

   An extensive shield of clouds/precip is apparent in a prefrontal
   low-level warm-advection/moisture-transport zone from eastern TN
   northward over much of KY/OH/IN.  A narrow corridor of
   destabilization is expected behind this precip and ahead of the
   low/front today, related to pockets of surface-diabatic heating and
   theta-e advection in the warm sector.  This and weak MLCINH will
   offset modest midlevel lapse rates enough to support scattered
   thunderstorms along/ahead of the surface cold front, including
   prefrontal confluence/convergence lines.  Convection generally will
   assume quasi-linear configurations with embedded LEWPs, bowing
   segments, and perhaps a few supercells possible.

   The environment will be characterized by strong deep-layer/speed
   shear and modest but sufficient buoyancy, with 500-mb winds
   strengthening to more than 70 kt over much of the central
   Appalachians region, and 45-60 kt of 850-mb flow crossing the same
   area. Buoyancy fields will be rather fragmented, but with general
   500-1000 J/jg MLCAPE values spreading northeastward over eastern
   KY/OH and over areas from the Blue Ridge eastward.  A relative min
   in low-level theta-e and buoyancy is likely in higher elevations
   from southwestern VA northeastward, but with at least marginal
   instability to support convection.  Bands of convection should
   shift/form east of the mountains with time as well, also offering a
   dominant wind threat and secondary tornado potential in the
   strong-shear environment.  Overall severe potential is expected to
   diminish after dark, and as the stronger upper support and mass
   response ejects northeastward in step with the trough aloft.

   ..Edwards/Wendt.. 04/14/2019