SPC AC 312134

   Day 1 Convective Outlook AMEND 1
   NWS Storm Prediction Center Norman OK
   0434 PM CDT Mon Aug 31 2020

   Valid 312000Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST
   KANSAS INTO A PORTION OF OKLAHOMA AND NORTHERN TEXAS...

   AMENDED TO INTRODUCE TORNADO PROBABILITIES FOR A SMALL AREA IN
   SOUTHERN VIRGINIA AND NORTHERN NORTH CAROLINA

   ...SUMMARY...
   Scattered severe thunderstorms remain possible this evening into
   tonight, mainly from southwest Missouri, southeast Kansas through
   Oklahoma and into north Texas. Damaging winds, large hail, and a
   couple tornadoes are the expected hazards. A brief tornado or two is
   also possible over southern Virginia and extreme northern North
   Carolina

   ...Discussion...

   Primary change to previous outlook has been to remove the SLGT from
   that portion of southeast MO that has been stabilized/overturned.
   Otherwise, primary severe threat is expected to evolve from
   southeast KS through OK into northern TX as storms develop along a
   slow moving cold front. Deeper ascent associated with an eastward
   advancing shortwave trough currently situated over the southern High
   Plains will interact with the front and foster thunderstorm
   initiation along this boundary by early evening. Effective bulk
   shear from 30-40 kt suggests some updrafts might develop rotation
   with initial discrete modes, but an eventual evolution to an MCS is
   expected. Damaging wind and large hail are the main threats, but a
   small window will exist for a couple of tornadoes this evening.


   Storm moving east along warm front over southern VA might remain
   capable of producing a brief tornado or two through 23 or 00Z. Have
   introduced 2% probability to cover this scenario. Reference SWOMCD
   1657 for additional information.

   ..Dial.. 08/31/2020

   .PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Aug 31 2020/

   ...South-central States...
   A cluster of strong to locally severe thunderstorms is ongoing in
   MO, while remnants of a decayed cluster are shifting east from
   eastern AR. Damaging winds will remain the primary hazard with the
   northern cluster as it likely spreads across the rest of southern MO
   through mid-afternoon. It should weaken as it encounters the
   outflow/recently overturned air mass in AR. Locally damaging winds
   may also occur with potential intensification along remnant outflows
   that shift east of the Lower MS Valley towards the TN Valley through
   the afternoon.

   Otherwise, scattered thunderstorms are expected to develop along and
   just ahead of a pronounced cold front that currently arcs from
   southeast KS into the TX South Plains. The most likely corridors of
   initiation at peak heating are over the Low Rolling Plains of
   northwest TX and in central OK. A belt of confluent mid-level
   west-southwesterlies across this portion of the front will support a
   predominant cluster mode. A few supercells are most likely in the
   early initiation phase in the central OK vicinity with large hail to
   around 2 inches and a tornado or two possible. Upscale growth into a
   broader cluster/MCS appears possible into south-central/southeast OK
   vicinity. The high PW/CAPE air mass could support isolated
   significant severe wind gusts in this region during the evening into
   tonight.

   ...Western/central NC vicinity...
   Regenerative convection along the southern periphery of a broader
   stratiform region in VA may pose a risk for localized damaging winds
   into early evening. Northern SC into central NC may have the most
   persistent area of convection as downstream boundary-layer heating
   is more pronounced relative to the pervasive cloudiness closer to
   the higher terrain. Poor mid-level lapse rates sampled in area 12Z
   soundings and stronger low-level flow confined north in the lee of
   the central Appalachians suggest that convective vigor should remain
   limited.

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z