SPC AC 041730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1230 PM CDT Sat May 04 2024

   Valid 051200Z - 061200Z

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

   ...SUMMARY...
   Strong to severe thunderstorms may occur Sunday across parts of the
   southern Plains into the ArkLaTex and Mid-South, and separately over
   portions of Ohio into western Pennsylvania. Highest severe
   thunderstorm potential is expected from the Texas Hill Country into
   the Middle Texas Coastal Plain.

   ...Synopsis...
   A southern-stream shortwave trough, likely enhanced somewhat by
   widespread thunderstorms Saturday night, is expected to begin the
   period extended from central OK through southeast TX. This shortwave
   is forecast to make steady northeastward progress throughout the
   day, reaching the Lower OH Valley by late Sunday night/early Monday
   morning. A separate north-stream shortwave trough will likely will
   move across Ontario and western Quebec, with an attendant surface
   low moving just ahead of this wave. An associated cold front will
   extend southwestward from this low, and is expected to progress
   eastward across the OH Valley throughout the day. Southern portion
   of this front (i.e. from the Mid-South into central TX) will remain
   largely stationary throughout the day, before then transitioning to
   a warm front amid strengthening return flow overnight. 

   Farther west, a deep upper cyclone is forecast to progress eastward
   across the Great Basin before devolving into more of an open wave as
   it moves through the central Rockies and into the central High
   Plains. Strong mid-level flow will accompany this system, spreading
   eastward and reaching the southern/central High Plains by early
   Monday morning.

   ...Southern Plains into the ArkLaTex and Mid-South...
   Showers and thunderstorms will likely be ongoing from eastern OK
   into central and southeast TX at the start of the period early
   Sunday morning, although with varying convective modes.  A more
   linear, modestly organized convective line may be ongoing across
   southeast TX, remnant from Saturday night/early Sunday morning
   activity across central TX. Gradually decreasing buoyancy should
   lead to gradual weakening of this line as it moves into
   west-central/southwest LA. Even so, given the potentially organized
   character to the line, some damaging gust will still be possible.

   A more multicellular mode is anticipated throughout the day from
   eastern OK into the Arklatex and Mid-South, supported by persistent
   forcing for ascent and modest buoyancy. A few stronger updrafts
   capable of hail are possible, with some limited potential for a few
   bowing segments capable of damaging gusts as well.

   Farther west, an outflow boundary is expected to extend westward
   from this decaying convective line, likely from the middle TX
   Coastal Plain through the Hill Country into the Edwards Plateau.
   This boundary will likely provide the focus for addition
   thunderstorm activity during afternoon. Ample low-level moisture,
   strong buoyancy, and moderate deep-layer shear support the potential
   for supercells with any discrete development. Large hail is primary
   hazard with initial development, but some trend towards upscale
   growth is likely, with the resulting convective line tracking along
   the outflow boundary. Mesoscale nature of this scenario does lead to
   some uncertainty, particularly on the location of the outflow
   boundary, but guidance is consistent enough to delineate higher
   probabilities from the TX Hill Country into the Middle TX Coastal
   Plain.

   ...Ohio into Western Pennsylvania...
   As mentioned in the synopsis, a weak front is forecast to move
   eastward across the OH Valley Sunday. Modest destabilization should
   occur ahead of this front across OH and western PA, contributing to
   the potential for isolated to scattered thunderstorms along and
   ahead of this boundary. Deep-layer shear of 20-30 kt should support
   marginal updraft organization, with occasionally strong to damaging
   gusts as these storms spread east-southeastward across parts of OH
   into western PA and vicinity Sunday afternoon and early evening.
   This activity should gradually weaken through the evening across PA
   as it encounters a less unstable airmass.

   ...Northern High Plains...
   Despite limited low-level moisture and scant buoyancy, increasing
   mid-level moisture and strengthening large-scale forcing for ascent
   ahead of the Great Basin shortwave is forecast to support the
   development of isolated thunderstorms late Sunday evening. Given the
   high storm bases and strengthening mid/upper flow, a few strong
   gusts are possible. Even so, the overall severe threat appears too
   limited to include low severe probabilities with this outlook.

   ..Mosier.. 05/04/2024

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