SPC AC 101954

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0254 PM CDT Sat Jun 10 2023

   Valid 102000Z - 111200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS
   AFTERNOON/EVENING FROM THE ARKLATEX INTO CENTRAL TEXAS...

   ...SUMMARY...
   Very large hail of 2-3 inches in diameter, damaging thunderstorm
   gusts of 60-75 mph, and a couple of tornadoes will be possible this
   afternoon through late evening from the ArkLaTex into central Texas.

   ...20Z Update...

   ...North/Central TX...
   Recent surface analysis places an outflow boundary from Wise County
   southeastward to Ellis/Navarro Counties and then back
   eastward/east-northeastward into northwest LA. Cumulus is developing
   along this boundary across the southern Metroplex vicinity, and the
   air mass here and south is strongly unstable (i.e. MLCAPE 2500+
   J/kg). An initially cellular mode is anticipated, with some
   supercells possible. Very large hail will be primary threat, but a
   tornado or two is also possible if any storms interact with the
   outflow boundary. Expectation is for eventual upscale growth, with
   the line then moving southeastward into east/southeast TX. The
   threat would transition to damaging gusts during that time, with a
   few gusts from 60-75 mph are possible. This area was also addressed
   in recently issued MCD #964 and Severe Thunderstorm Watch 262.

   ...Central Plains/Central High Plains...
   Overall expectations across the central High Plains and central
   Plains have not changed. Across the central High Plains,
   thunderstorms expected to come off the higher terrain and move into
   the lower elevations, with an attendant threat for damaging gusts.
   Over the central Plains, a strong storm or two is still possible
   this evening and overnight as a cold front pushes through the
   region.

   ..Mosier.. 06/10/2023

   .PREV DISCUSSION... /ISSUED 1131 AM CDT Sat Jun 10 2023/

   ...Southern Plains to the lower MS Valley through late evening...
   A cluster of thunderstorms is moving southeastward across the
   ArkLaTex as of late morning, with an MCV over eastern OK (trailing
   the initial convection/outflow).  Surface temperatures are warming
   into the 80s with boundary-layer dewpoints in the low 70s from
   northeast TX into northern LA/southern AR, which is boosting MLCAPE
   to the 2000-3000 J/kg range.  Vertical shear remains relatively weak
   near and ahead of the primary convective band along the outflow, and
   the strongest updrafts should remain along the southern flank of the
   cluster.  Thus, the expectation is for occasional damaging gusts
   with precipitation-loaded downdrafts, with a somewhat
   outflow-dominant structure to the cluster as is moves southeastward
   through the afternoon.  Other, more isolated storm clusters with
   isolated downburst potential, may occur this afternoon along the
   instability gradient into MS.

   Farther west, outflow with the morning cluster is moving southward
   into north TX.  Strong surface heating and a feed of steep midlevel
   lapse rates from the west will contribute to strong buoyancy (MLCAPE
   > 3000 J/kg) this afternoon, along and south of the outflow
   boundary.  Additional thunderstorm development appears probable by
   mid-late afternoon along the slowing outflow, and storms will
   subsequently spread southeastward toward southeast TX before
   weakening early tonight.  Vertical shear will become sufficient for
   supercells along the outflow boundary as a weak midlevel
   trough/speed max moves eastward over TX within the southern stream. 
   The steep lapse rates/large buoyancy, in combination with mainly
   straight hodographs and effective bulk shear of 35-40 kt, will
   support supercell clusters capable of producing isolated very large
   hail of 2-3 inches in diameter.  Some upscale growth will be
   possible this evening, with a corresponding increase in the threat
   for damaging outflow gusts.  Any tornado threat will rely on
   favorable storm interactions with locally backed flow/stronger
   low-level shear along the modifying outflow boundary late this
   afternoon. 

   ...Central Plains this afternoon into tonight...
   Scattered thunderstorms are expected this afternoon across the
   central Plains in associated with remnant MCVs and differential
   heating zones.  Buoyancy and vertical shear will not be strong, but
   isolated/marginal hail/wind events will be possible.  Other clusters
   of storms may form across the High Plains and move
   east-southeastward this evening into tonight.  These storms may
   produce isolated strong-severe outflow gusts from eastern CO into
   KS.

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