SPC AC 230607

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0107 AM CDT Thu May 23 2019

   Valid 231200Z - 241200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PORTIONS
   OF THE TEXAS PANHANDLE NORTHEASTWARD INTO KANSAS AND ACROSS PORTIONS
   OF PENNSYLVANIA AND MARYLAND...

   ...SUMMARY...
   Severe storms with large hail, damaging wind and tornadoes will be
   possible over a part of the central and southern Plains Thursday and
   from the Ohio Valley into the northern Mid-Atlantic.

   ...Southern and central Plains...
   Convection should be ongoing or just developing at the beginning of
   the forecast period across portions of the TX/OK Panhandles as
   moisture retreats westward south of a weak surface boundary in the
   area.  Over time, these storms should grow upscale into one or two
   linear complexes while migrating east-northeastward toward
   south-central Kansas during the afternoon.  The surface boundary
   will also evolve into a warm front and migrate north toward Kansas
   ahead of the complex - in part due to 35-45 kt southerly flow at 850
   hPa.  By afternoon, moderate to strong instability in the
   pre-convective warm sector should support a damaging-wind and
   tornado threat along the leading edge of the expected linear
   complex(es), with this threat shifting into eastern Kansas during
   the evening.

   A convectively modified surface boundary should stall in the general
   vicinity of the Texas Panhandle and adjacent northwest Oklahoma
   through the afternoon.  Shortwave troughs migrating through the
   southeastern extent of an amplifying mid-level trough in the
   Southwest will interact with the strongly unstable warm sector and
   result in scattered to numerous thunderstorms.  These storms should
   exist in an environment containing strong deep shear and weak
   mid-level inhibition, with strengthening low-level shear developing
   toward 23-02Z in response to a 40-50 kt 850 hPa jet stream across
   western Oklahoma.  Cells should have a propensity to rotate and
   produce all modes of severe, with the tornado threat maximized
   during this time.  The trajectory of these storms should take them
   northeastward toward and over the remnant cold pool from earlier MCS
   activity.  With widespread convection expected, some upscale growth
   may also occur across the eastern Texas Panhandle and western
   Oklahoma late in the forecast period, with a resultant damaging
   wind, hail, and isolated tornado threat overnight.  Additional
   storms are expected to develop as far southwest as southeastern New
   Mexico and adjacent portions of the Texas South Plains overnight,
   with more isolated activity expected southward toward the Big Bend
   area.

   ...Upper Ohio Valley eastward toward New York, Pennsylvania, and
   Maryland...
   The forecast in this region will be somewhat complicated by
   mid-morning to mid-day convection expected to traverse the region
   from west to east - particularly across Pennsylvania.  Nevertheless,
   models indicate the development of weak to moderate instability
   ahead of a cold front that will migrate southward across the region.
    This destabilization will occur amidst a strongly sheared airmass,
   with 30-40 kt westerly 850 hPa flow veering and strengthening to
   northwesterly aloft.  Convection is expected to evolve into a series
   of mixed modes (both linear and cellular) with tornadoes, hail, and
   damaging wind gusts all possible.  Convection will migrate
   southeastward toward Maryland, Delaware, and New Jersey during the
   evening before waning with near-surface stabilization late in the
   period.

   ..Cook.. 05/23/2019

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