SPC AC 280554

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1254 AM CDT Thu May 28 2020

   Valid 281200Z - 291200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE CENTRAL GULF STATES AND SOUTHWESTERN TEXAS...

   ...SUMMARY...
   Isolated severe thunderstorms are possible across portions of
   southwestern Texas and over the central Gulf States. Hail and wind
   are the main threats.

   ...Central Gulf States...

   Slow-moving upper trough is forecast to shift across the Mid-South
   into the TN Valley by the end of the day1 period as somewhat
   stronger mid-level flow begins to translate into the downstream
   portion of this feature. Latest model guidance suggests substantial
   breaks in cloud cover will be noted across MS/AL region which should
   allow for stronger boundary-layer heating than surrounding areas. As
   a result, steeper low-level lapse rates and greater buoyancy is
   expected to develop by early afternoon. This regional pocket of
   instability should prove favorable for isolated robust thunderstorm
   development as 40kt 500mb flow translates across the central Gulf
   States. Forecast soundings suggest hail/wind may accompany storms
   across this region.

   ...Southwestern TX...

   While weak large-scale height rises are forecast across TX, there is
   some indication a weak short-wave trough will dig across the TX
   South Plains during the afternoon which may encourage convective
   development just north of the international border ahead of a
   reinforcing frontal surge. Although low-level convergence is not
   expected to be particularly strong along the wind shift, strong
   boundary-layer heating is expected across the High Plains, extending
   into the Big Bend region of TX. Latest CAMs support isolated
   strong/severe thunderstorm development by late afternoon along the
   I-10 corridor of southwestern TX. This activity will propagate south
   into northern Mexico along a substantial instability axis
   characterized by surface-6km shear around 35-40kt. If sufficient
   clustering materializes west of the Rio Grande River, there would be
   some opportunity for propagation back across the river into portions
   of deep south TX. This scenario is too uncertain to expand higher
   severe probs too far east.

   ...Elsewhere...

   A few strong-locally severe thunderstorms are possible across
   portions of the Gulf States, north into central PA. Most of this
   region will experience weak height rises in the wake of an early-day
   short-wave trough that should eject across PA into NY during the
   afternoon. Generally weak buoyancy, poor lapse rates, and lack of
   forcing lend too much uncertainty for more than low severe
   probabilities.

   ..Darrow/Lyons.. 05/28/2020

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z