SPC AC 271955

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0255 PM CDT Sat Mar 27 2021

   Valid 272000Z - 281200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO TONIGHT FROM PARTS OF THE ARK-LA-TEX ACROSS THE MID SOUTH AND
   TN VALLEY...

   ...SUMMARY...
   Severe storms are likely this afternoon into tonight from the
   Ark-La-Tex east-northeastward across parts of the Mid South and
   Tennessee Valley. All hazards are possible including very large
   hail, significant damaging winds, and a couple of strong tornadoes.

   Only minor changes have been made to adjust for the ongoing cluster
   of storms moving east across North Carolina. Elsewhere, the forecast
   remains on track. See the previous discussion for more details.

   ..Wendt.. 03/27/2021

   .PREV DISCUSSION... /ISSUED 1124 AM CDT Sat Mar 27 2021/

   ...Mid South/TN Valley region through tonight...
   Elevated convection with a marginal hail threat that formed
   overnight in a zone of warm advection, along and north of the
   surface warm front from the Mid South into middle/eastern TN,
   persists as of late morning.  The convection is also associated with
   a subtle mid-upper speed max moving east-northeastward over the Mid
   South.  Farther west, additional storm development is expected by
   early-mid afternoon along the rain-reinforced front close to the
   MS/AL/TN border region.  This afternoon convection will likely be
   rooted at the surface as the low levels continue to warm/moisten
   from the south, with a few supercells possible with MLCAPE near 2000
   J/kg, effective bulk shear near 50 kt, and effective SRH around 150
   m2/s2.

   Farther west into northeast TX and southern/eastern AR,
   surface-based supercell development is expected by mid afternoon
   along the moisture gradient/warm front, as the low levels continue
   to destabilize and the cap weakens.  The forcing for ascent will be
   rather subtle, so the primary storm mode should be a mix of discrete
   supercells and clusters moving east-northeastward along the buoyancy
   gradient/front this afternoon into early tonight.  Isolated very
   large hail, damaging winds, and a couple of tornadoes will be the
   main concerns this afternoon.  Some increase in low-level shear is
   expected this evening, which will support an increase in the tornado
   threat, with an isolated strong tornado or two possible.  Otherwise,
   storms overnight should consolidate into more of a solid band as the
   synoptic cold front overtakes the convection from the northwest, in
   response to phasing of the northern and southern streams, with
   cyclogenesis from IL to Lower MI.

   ...Eastern OK/northwestern AR to IL this afternoon/evening...
   The primary surface cyclone is expected to begin deepening this
   evening across IL, before moving to Lower MI overnight.  In the wake
   of the low, a cold front will begin to accelerate southeastward
   later this evening into tonight.  The primary uncertainties along
   this corridor are the degree of low-level
   moistening/destabilization, and the magnitude of the low-level
   shear.  The main low-level mass response/low-level jet will likely
   be directed into the rather persistent zone of convection farther to
   the southeast along the effective warm front from northeast TX to
   western TN.  These factors suggest substantial limitations to the
   wind/hail threat along the cold front farther to the northwest, with
   the most questionable area centered on northwestern AR.

   ...Carolinas this afternoon/evening...
   The cluster of storms in eastern TN has been elevated through the
   morning, but some northward expansion of the surface warm sector is
   expected through this afternoon from SC into NC.  Given sufficient
   deep-layer vertical shear, an organized cluster with some threat for
   damaging winds/large hail may persist into the afternoon along the
   warm front from the Piedmont eastward across NC and adjacent
   portions of SC.

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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