SPC AC 031629

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1129 AM CDT Wed Apr 03 2019

   Valid 031630Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EASTERN TX/OK
   PANHANDLES AND WESTERN OK...

   ...SUMMARY...
   Severe thunderstorms are most likely across the eastern Texas and
   Oklahoma Panhandles into western Oklahoma between 4 to 10 PM CDT.
   Large hail and severe wind gusts should be the primary hazards.

   ...TX/OK Panhandles and western OK...
   Primary changes are to increase wind probabilities to account for
   severe gust potential and add a significant severe hail area for the
   most probable discrete supercell location.

   A shortwave trough over the Four Corners will progress east and
   reach western OK early Thursday. Lee cyclogenesis is underway near
   the Raton Mesa and this low will move southeast across the TX
   Panhandle through this evening. The cyclone will continue to drift
   east towards southwest OK, but also weaken given the lack of a
   pronounced baroclinic zone (which is evidence of a decaying
   baroclinic wave aloft). The lee cyclone will draw a modifying Gulf
   air mass northward across central TX to the east of a sharpening lee
   trough/dryline that should lie from the Caprock south-southwest
   across the Concho Valley by late afternoon.  

   The low-level moisture return will remain rather modest, with mid
   50s boundary-layer dewpoints currently confined to the Edwards
   Plateau south. The NAM still appears to be too aggressive with
   low-level saturation (and possible drizzle) keeping afternoon
   surface temperatures in the 50s across a large portion of OK (which
   is at or below current temperatures). The expectation is for
   temperatures to warm into the low-mid 80s west of the dryline from
   the South Plains south. In conjunction with very steep mid-level
   lapse rates around 9 C/km, MLCAPE around 1000 J/kg is anticipated
   northeast of the surface thermal ridge.

   Forcing for ascent with the approaching mid-level trough should help
   weaken the cap and support thunderstorm development after 20Z along
   the dryline in the Panhandles. Vertical shear will be favorable for
   discrete supercells, especially from the Amarillo to Childress
   vicinity. HREF members are highly consistent in depicting potential
   for a couple discrete supercells along the southern edge of storm
   development. Low-level shear will increase this evening across
   southwest OK/northwest TX. However, the marginal moisture return,
   substantial capping with southern extent, and poor 0-3 km lapse
   rates where MLCIN is weaker all suggest a limited tornado risk
   should be confined to early evening.

   ...OK to AR/northern LA overnight...
   Some of the initial dryline convection could persist into the
   evening near and north of I-40 in OK, with a continuing threat for
   hail with what will become elevated storms. Additional elevated
   convection could form late tonight from northeast TX into eastern
   OK/AR/northern LA. Warm advection on the nose of a 40-50 kt
   southwesterly low-level jet and the leading edge of the deeper
   returning moisture, along with MUCAPE from 1000-1500 J/kg, may
   support a threat for isolated severe hail from 06-12Z.

   ..Grams/Mosier.. 04/03/2019

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