SPC AC 071218

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0718 AM CDT Tue May 07 2019

   Valid 071300Z - 081200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THE
   CENTRAL/EASTERN TX PANHANDLE AND EXTREME WESTERN OK THIS AFTERNOON
   INTO EARLY TONIGHT...

   ...SUMMARY...
   Numerous severe storms are expected this afternoon into early
   tonight across the Texas Panhandle into extreme western Oklahoma.  A
   couple of strong tornadoes, very large hail, and damaging winds will
   all be possible.

   ...Southern High Plains and vicinity through tonight...
   The synoptic front extends from northern MO to the northern TX
   Panhandle, though the effective front is located farther south into
   northern OK, as a result of outflow from overnight convection that
   has mostly weakened.  Cyclogenesis is expected today along the
   boundary into northeast NM in advance of a midlevel trough crossing
   AZ/NM, with a sharpening dryline to the south near the TX/NM border.
   Mass response to the cyclogenesis will draw boundary-layer dewpoints
   in the 60s northwestward into west TX and the TX Panhandle, beneath
   a plume of steep (8-9 C/km) midlevel lapse rates.  This will drive
   moderate-strong buoyancy (MLCAPE of 2000-3000 J/kg) in the warm
   sector east of the dryline, with weakening convective inhibition by
   early-mid afternoon.

   Some consolidation of the residual outflows and the synoptic front
   is expected today into KS.  This front and the dryline will focus
   severe storm development today, with the earlier development
   expected near the front across the northern TX and OK Panhandles
   into southwest KS.  An increase in ascent from west-to-east during
   the afternoon and daytime heating/mixing in cloud breaks will weaken
   the cap such that storm initiation is likely by mid afternoon along
   and east of the dryline.  The initial convection will remain
   semi-discrete for a few hours into this evening, in an environment
   increasingly favorable for right-moving supercells capable of
   producing very large hail as deep-layer vertical shear increases. 
   An increase in low-level shear is also expected later this
   afternoon/evening in the warm sector, with effective SRH likely in
   excess of 200 m2/s2.  The semi-discrete storm mode with increasing
   low-level shear in a sufficiently moist environment will support
   tornadic supercells, with the potential for a couple of strong
   tornadoes.

   Upscale growth into clusters and eventually a more extensive QLCS is
   expected by late evening into the overnight hours from northwest TX
   into western/central OK and southern KS.  Damaging winds will become
   a more substantial threat will embedded supercells/bowing segments
   tonight, though large hail will remain possible.  A couple of
   tornadoes and/or severe gusts may also occur with circulations
   embedded within the QLCS.

   ..Thompson/Smith.. 05/07/2019

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