SPC AC 301728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Tue Mar 30 2021

   Valid 311200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
   SOUTHEAST...

   ...SUMMARY...
   Organized severe thunderstorms are possible on Wednesday across
   portions of the Southeast, with damaging gusts the primary severe
   threat. More isolated severe storms are also possible across parts
   of the Mid Atlantic, with the severe threat potentially continuing
   after dark.

   ...Synopsis...
   An upper trough will continue to amplify while progressing eastward
   across the Ohio Valley towards the Atlantic coastline tomorrow
   (Wednesday). During the late morning/early afternoon, a surface low
   is expected to gradually develop in advance of the upper trough
   across the central Appalachians and move northeastward towards lower
   New England while an associated cold front will sag southward across
   the Southeast. Isolated to scattered thunderstorm development is
   expected ahead of the aforementioned surface low across the lower
   Hudson Valley and along the front extending into Texas. At the
   moment, buoyancy appears to be greatest across portions of
   Mississippi, Alabama, and Georgia, where the greatest coverage for
   thunderstorms and associated risk for severe is currently expected.
   However, while buoyancy is weaker across portions of the Carolina
   Piedmont into the Mid Atlantic, stronger dynamic forcing for ascent
   and kinematic fields may promote at least isolated severe storm
   development across this area as well.

   ...Portions of the Southeast U.S...
   Stronger flow aloft and associated upper support is expected to lag
   the surface cold front and remain roughly parallel to the baroclinic
   zone, likely promoting linear convective structures along the front
   forced primarily by low-level convergence. Nonetheless, deep
   moisture (characterized by upper 60s F dewpoints), and the presence
   of a diurnally heated/mixed boundary layer promoting 7.5 C/km
   low-level lapse rates are expected to foster 1000-1500 J/kg MLCAPE
   by late morning/early afternoon. The available instability and mixed
   boundary layer should support the potential for organized damaging
   gusts, with a Slight risk introduced. 6.5 C/km mid-level lapse rates
   and linear forcing suggest that marginally severe hail is possible,
   albeit on a more isolated basis. Lastly, a few CAMS have hinted at
   one or two discrete cells initiating ahead of the front. Should
   mature/sustained pre-frontal convection develop, enough low-level
   speed and directional shear will be present to support brief,
   transient rotation and a brief tornado cannot be completely ruled
   out. 

   ...Portions of the Carolina Piedmont into the Mid Atlantic...
   By mid afternoon extending into the evening hours, scattered
   thunderstorm development is expected within a confluence zone ahead
   of the approaching surface low. Compared to areas farther southwest,
   upper flow will be more perpendicular to the cold front/surface lee
   troughing, with deep-layer ascent overspreading the area. A 30-40 kt
   low-level jet will also be in place, fostering up to 150-250 m2/s2
   effective SRH, suggesting that storm organization and transient
   low-level rotation is possible. However, instability is expected to
   be marginal despite mid 60s F dewpoints. Mediocre low and mid-level
   lapse rates currently support tall-skinny MLCAPE profiles,
   suggesting that the overall severe threat should be relatively
   localized/brief in nature. However, any storm that can manage to
   become organized/sustained may pose a threat for damaging gusts and
   perhaps a tornado.

   ..Squitieri/Gleason.. 03/30/2021

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