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    Day 2 Outlook >
Oct 23, 2017 2000 UTC Day 1 Convective Outlook
Updated: Mon Oct 23 19:42:34 UTC 2017 (Print Version | 20171023 2000Z Day 1 shapefile | 20171023 2000Z Day 1 KML)
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 Forecast Discussion
   SPC AC 231942

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0242 PM CDT Mon Oct 23 2017

   Valid 232000Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CAROLINAS
   INTO A PORTION OF VIRGINIA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
   OF THE SOUTHEAST STATES INTO THE MID ATLANTIC...

   ...SUMMARY...
   Isolated strong to severe storms should persist over the Carolinas
   this afternoon into the evening, but also spreading into the
   Mid-Atlantic during the evening. The main threats will be damaging
   wind gusts and a few tornadoes.

   ...Carolinas through Mid Atlantic...

   Only minor adjustments have been made to previous forecast. Bands of
   low topped storms will persist this afternoon and evening within
   corridor of deep ascent associated with a progressive, negative-tilt
   shortwave trough. Latest objective analysis shows MLCAPE from near
   300 J/kg over west central NC to 500 J/kg across SC. Storms are
   embedded within strong winds aloft and vertical shear profiles with
   large hodographs (400-600 m2/s2 0-1 km storm relative helicity).
   Occasional organized storms including a few supercells and bowing
   segments will persist as activity gradually spreads east and
   northeast into the evening.

   ..Dial.. 10/23/2017

   .PREV DISCUSSION... /ISSUED 1104 AM CDT Mon Oct 23 2017/

   ...Carolinas and vicinity through tonight...
   A midlevel shortwave trough over the TN Valley this morning will
   eject northeastward to the southern Appalachians this
   afternoon/evening, and continue north-northeastward to the central
   Appalachians and upper OH Valley tonight, in response to an
   amplifying upstream trough over the MS Valley.  An associated
   surface cyclone in central IN will move north-northeastward and
   deepen across Lower MI and the upper Great Lakes by tonight, as a
   trailing cold front progresses eastward to the southeast Atlantic
   coast and Mid-Atlantic region.  Ahead of the cold front, the moist
   warm sector will spread northward across NC today and VA by tonight,
   with the more unstable warm sector limited to areas east-southeast
   of a secondary low across western NC this afternoon/evening.

   Regional 12z soundings and radar/satellite imagery show a widespread
   band of clouds/rainfall preceding the cold front, where surface
   heating will be limited and lapse rates will remain rather poor. 
   Still, the rich low-level moisture (boundary-layer dewpoints of
   68-72 F) will contribute to weak surface-based buoyancy into the
   western Carolinas (SBCAPE 250-500 J/kg), and somewhat greater
   buoyancy into SC (1000-1500 J/kg).  At the same time, low-level
   shear will become quite strong (0-1 km SRH of 250-500 m2/s2), which
   will support strengthening of convection in a band with some breaks
   along the front this afternoon from eastern GA into the western and
   central Carolinas.  Embedded supercells and LEWP structures will be
   capable of producing a few tornadoes and damaging gusts, likely
   beginning by 18-20z in the vicinity of the Savannah River, and then
   spreading eastward-northeastward through this evening.

   Weaker low-level lapse rates and near-surface-based buoyancy will
   tend to limit the severe-storm threat with northward extent tonight
   into VA.  Still, a line of storms in the presence of very strong
   low-midlevel flow/shear and moist profiles will pose some threat for
   isolated damaging winds and a tornado or two.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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

        
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Page last modified: October 23, 2017
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