SPC AC 200558

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1258 AM CDT Thu Jun 20 2019

   Valid 201200Z - 211200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CAROLINAS AND SOUTHERN VIRGINIA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE MID MISSOURI VALLEY AND CENTRAL HIGH PLAINS...

   ...SUMMARY...
   Thunderstorms associated with damaging wind gusts and hail are
   likely today across parts of the Carolinas into the Middle Atlantic
   and Southeast. Isolated severe storms may also develop across parts
   of the Great Plains and Mid Missouri Valley.

   ...Eastern States...
   An upper-level trough will move eastward from the Ohio and Tennessee
   Valleys across the Southern and Central Appalachians into the
   Carolinas today. Ahead of the trough, a moist airmass will be in
   place from Georgia northeastward across the Carolinas into the
   Mid-Atlantic with surface dewpoints in the upper 60s and lower 70s
   F. In response, a large corridor of moderate instability is forecast
   to develop from the southern Appalachian foothills eastward to the
   Atlantic coast. Thunderstorms appear likely to initiate and organize
   just ahead of the shortwave trough in the southern Appalachians
   around midday with this activity moving eastward into the foothills
   during the afternoon. Forecast soundings in the foothills in
   northwestern South Carolina and west-central North Carolina at 21Z
   show MLCAPE values reaching 2,000 J/kg with 0-6 km shear of 30-35
   kt. This combined with veered southwesterly winds at the surface and
   westerly flow in the low to mid-levels will be favorable for
   quasi-linear development. As low-level lapse rates become steep in
   the afternoon, conditions will become favorable for wind damage
   along the leading edge of an MCS moving eastward away from the
   southern Appalachians. For this reason, will upgrade to Enhanced
   risk for wind damage across parts of northern South Carolina, North
   Carolina and southern Virginia. Isolated large hail will also be
   possible with the stronger parts of the linear MCS.

   Further north into the Mid-Atlantic, instability is not forecast to
   be quite as strong as across the Carolinas. For that reason, the
   wind damage threat is expected to remain more isolated and will
   depend upon which areas destabilize the most. Wind damage would be
   the primary threat across the Mid-Atlantic this afternoon.

   ...Mid-Missouri Valley...
   Westerly mid-level flow will be in place in the central U.S. today
   as a shortwave ridge develops across the central and northern
   Plains. Beneath the ridge, an axis of moderate to strong instability
   is forecast to develop ahead of a cold front from Kansas northward
   into the mid Missouri Valley. Convection appears likely to initiate
   along the front with thunderstorms moving eastward across parts of
   eastern Nebraska and western Iowa during the late afternoon.
   Forecast soundings at 21Z for Omaha, Nebraska and Kansas City,
   Missouri show MLCAPE reaching 2,500 J/kg and have strong deep-layer
   shear profiles. 0-6 km shear is forecast to be around 55 kt at both
   locations suggesting that supercells will be the likely storm mode.
   Convective coverage should remain relatively isolated due to a weak
   cap but any cells that can initiate and mature should have severe
   potential. The strong instability combined with steep low to
   mid-level lapse rates would be favorable for wind damage and large
   hail. A brief tornado would also be possible with supercells mainly
   during the early evening as low-level flow increases across the
   region.

   ...Central High Plains...
   Mid-level flow is forecast to become west-southwesterly today across
   the central High Plains in the wake of a developing upper-level
   ridge in the mid Missouri Valley. At the surface, backed
   east-southeasterly flow will be in place which will reinforce an
   axis of moisture and instability from southern Kansas extending
   northwestward into northeastern Colorado and western Nebraska. As
   surface temperatures warm, convection will initiate in the higher
   terrain of northeastern Colorado and spread eastward into the
   central High Plains this afternoon. Steep low to mid-level lapse
   rates and moderate to strong deep-layer shear, evident on forecast
   soundings, will be favorable for severe storms. Dry air in the
   low-levels may contribute to downburst potential but isolated large
   hail will be possible especially if a supercell can develop.

   ..Broyles/Squitieri.. 06/20/2019

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