SPC AC 051951

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0251 PM CDT Sun May 05 2024

   Valid 052000Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTH TEXAS
   INTO THE MIDDLE TEXAS COASTAL PLAIN...

   ...SUMMARY...
   Scattered severe thunderstorms are possible across parts of
   south-central Texas eastward into parts of southeast Texas, mainly
   this afternoon and early evening.

   ...20Z Update...
   Primary change with this update was to increase severe probabilities
   across the Arklatex region. 

   ..Arklatex..
   Low-level moisture continues to quickly advect northward into the
   region, with a resulting increase in buoyancy as well. Recent
   surface analysis places a weak low over far southeast OK, with
   modest troughing extending southwestward from this low. An effective
   warm front also extends southeastward from this low, coincident with
   the leading edge of the better low-level moisture. Interaction of
   these surface features with the destabilizing airmass could result
   in thunderstorm development. Vertical shear is strong enough to
   support organized storm structures, and a few storms may be able to
   produce hail and/or damaging as well as a brief tornado.

   ...Elsewhere...
   Forecast outlined in the previous outlook (appended below) remains
   valid for South TX, where supercells capable of large to very large
   hail and damaging gusts are ongoing. These will likely continue for
   the next few hours while slowly progressing southward.

   Also, as discussed in the previous outlook and recently issued MD
   #640, the potential for isolated damaging gust will persist across
   the Upper OH Valley into the early evening.

   ..Mosier.. 05/05/2024

   .PREV DISCUSSION... /ISSUED 1129 AM CDT Sun May 05 2024/

   ...South TX to Mid-South/lower Mississippi Valley...
   An ongoing linear sub-severe MCS over AR moving north-northeast will
   likely continue into portions of northeast AR/southeast MO and
   adjacent parts of KY/TN through mid afternoon.  Some additional
   heating may lead to some invigoration of storms along the leading
   edge of outflow with a localized strong/severe risk.  Farther
   southwest across south-central into southeast TX, an earlier MCV
   over western LA and convective overturning from overnight
   thunderstorm activity has left a remnant outflow boundary draped
   across southeast TX.  South of the boundary, a very moisture-rich
   airmass (16 g/kg lowest 100mb mean mixing ratios) beneath a residual
   plume of steep 700-500 mb lapse rates, are contributing to moderate
   to strong buoyancy.  

   Water-vapor imagery shows a mid- to upper-level impulse moving east
   over northern Mexico and into south-central TX late this morning. 
   Recent thunderstorm development over south-central TX to the middle
   TX coast may be in part due to ascent related to this upper feature.
   Isolated to scattered thunderstorms will probably continue to
   intensify with severe multicells or supercells with large hail,
   damaging gusts and at least marginal tornado potential this
   afternoon.  In the absence of notable mid/upper support behind the
   shortwave trough, convection may diminish rapidly through the
   evening, as the boundary layer stabilizes from both nocturnal
   cooling and spreading outflow air.

   ...Upper Ohio Valley vicinity...
   As a mid-level trough glances the region to the north over mainly
   southeast Canada, a surface front will provide a focus for lift and
   thunderstorm development this afternoon.  A plume of richer
   low-level moisture, characterized by lower 60s deg F surface
   dewpoints, is located ahead of the cold front and west of a
   north-south oriented warm front over western PA.  Continued heating
   will result in moderate buoyancy and favor the development of
   scattered thunderstorms.  Modest low to mid-level flow will limit
   overall storm intensity, but some multicellular organization is
   possible.  Isolated hail/damaging gusts will be the primary hazards
   with the stronger storms before this activity weakens by early
   evening.

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