SPC AC 171731

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 PM CDT Wed Mar 17 2021

   Valid 181200Z - 191200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   CENTRAL AND EASTERN GEORGIA INTO MUCH OF SOUTH CAROLINA AND NORTH
   CAROLINA...

   ...SUMMARY...
   A regional outbreak of severe storms and tornadoes is possible on
   Thursday from parts of east-central Georgia northeastward across
   South Carolina and North Carolina. Significant tornadoes, wind
   damage and large hail will be possible from morning into afternoon.
   Severe thunderstorms will also be possible from parts of the eastern
   Gulf Coast into the southern and central Appalachians.

   ...North Carolina/South Carolina/Georgia/Virginia/Florida...
   A positively-tilted upper-level low will move into the Tennessee
   Valley on Thursday as a 75 to 90 kt mid-level jet moves across the
   Southeast and Carolinas. At the surface, a low will move eastward
   into the central Appalachians. At 12Z, a warm front will be located
   from northern Georgia eastward across northern South Carolina. This
   boundary will move northward across central and eastern North
   Carolina during the morning. To the south of this front, surface
   dewpoints across the warm sector will be in the mid to upper 60s F.
   As surface temperatures warm, a pocket of moderate instability is
   expected to develop to the south of the warm front across eastern
   North Carolina by late morning. Convective development will be aided
   by the low-level jet. Severe thunderstorms associated with large
   hail, wind damage and a tornado threat, is expected during the mid
   morning hours.

   Further to the west, a band of large-scale ascent associated with
   the approaching upper-level system will overspread the central
   Appalachians around midday. Thunderstorms are expected to initiate
   just ahead of this band of ascent around midday and move eastward
   into the Appalachian foothills during the early afternoon. Ahead of
   the storms, the environment will consist of MLCAPE in the 2000 to
   2500 J/kg range, 0-6 km shear of 50 to 60 kt and storm relative
   helicities of 300 to 350 m2/s2. This will support intense supercell
   development. Tornadoes, wind damage and large hail will be likely
   with the stronger storms. A long-track tornado will be possible
   along or in the vicinity of the warm front. The time of maximum
   threat is forecast to be in the 18Z to 22Z time window. A regional
   outbreak of severe storms, along with several significant tornadoes
   are expected from discrete cells that develop across the warm sector
   from central North Carolina southward across much of South Carolina.

   Further to the southwest into Georgia, a line of strong to severe
   thunderstorms is expected to move into the area form the west during
   the morning. A corridor of moderate instability is forecast to
   develop just ahead of this line by late morning with instability
   continuing to increase through the afternoon. This line of storms
   will have access to a strong low-level jet, extending northeastward
   across south-central and eastern Georgia. the environment should
   have MLCAPE of 1500 to 2000 J/kg along with 0-6 Km shear of 60 to 70
   kt. This will be favorable for supercell and severe bowing line
   segments. Supercells that form in the line may produce tornadoes,
   wind damage and large hail. A potential for significant tornadoes
   will exist with cells that form at the north end of gaps in the
   line. This band of storms is expected to be accompanied by
   widespread wind damage, moving across eastern Georgia and South
   Carolina during the mid to late afternoon. Wind gusts of greater
   than 65 kt will be possible with the more intense bowing line
   segments. The southern part of the band may extend as far south as
   the Florida Panhandle, where a severe threat will exist in the
   morning and early afternoon.

   ...Upper Ohio Valley/Central Appalachians...
   An upper-level low will move eastward across the Tennessee Valley on
   Thursday. Ahead of the system, a line of strong thunderstorms may be
   ongoing at the start of the period from parts of far eastern
   Tennessee northward into far western Virginia. Behind the line,
   surface temperature will warm during the day resulting in a corridor
   of moderate instability, from eastern Kentucky into the western
   Virginias. The instability combined with strong large-scale ascent,
   steep mid-level lapse rates and 0-6 km shear of 50 to 60 kt will be
   favorable for severe storms. Large hail, wind damage and a tornado
   or two will be possible across the upper Ohio Valley during the
   afternoon.

   ..Broyles.. 03/17/2021

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