SPC AC 121727

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1227 PM CDT Tue Sep 12 2023

   Valid 131200Z - 141200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
   SOUTHERN NEW ENGLAND...COASTAL CAROLINAS...SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   Marginally severe thunderstorms are possible in parts of the
   southern High Plains, southern New England, and the Carolinas on
   Wednesday.

   ...Synopsis...
   An upper-level trough will move from the Great Lakes/Ohio Valley
   toward New England on Wednesday. Multiple vorticity maxima will be
   embedded within the midlevel southwesterly flow ahead of this
   trough. At the surface, a cold front will move across parts of the
   Northeast and Mid Atlantic into the southern Appalachians, with a
   weak frontal wave potentially moving from the Mid Atlantic into New
   England through the day. Farther west, a broad upper-level trough
   will remain in place across parts of the western/central CONUS, with
   one notable shortwave trough expected to move eastward from the
   southern Rockies into the southern Plains. 

   ...Northern NJ/Southeast NY into southern New England...
   A band of convection will likely be ongoing at the start of the
   forecast period somewhere across southeast NY/northern NJ into
   western parts of southern New England, aided by low-level warm
   advection and midlevel vorticity maxima ejecting northeastward ahead
   of the primary upper trough. Instability will generally remain weak,
   but moderate deep-layer shear, favorable moisture, and some
   enhancement of low-level shear/SRH within the warm-advection regime
   may support transient rotating cells capable of locally damaging
   gusts and/or a brief tornado. The primary threat may reside with the
   initial cluster of convection as it moves eastward across southern
   New England, though some redevelopment will be possible its wake,
   depending on timing of early convection and extent of
   destabilization in its wake. 

   ...Coastal Carolina vicinity...
   In advance of the large-scale trough to the north, one or more weak
   midlevel vorticity maxima may move across parts of the Carolinas
   Wednesday. These may aid in scattered afternoon thunderstorm
   development within a warm, moist, and moderately unstable
   environment during the afternoon. Modest westerly midlevel flow will
   support effective shear of 25-30 kt, sufficient for some storm
   organization, and a few semi-organized cells/clusters will be
   possible. A Marginal Risk has been added for parts of near-coastal
   SC and southern NC, where the best overlap of instability, shear,
   and storm coverage is currently anticipated. 

   ...Southern High Plains vicinity...
   Scattered thunderstorms are expected from the southern Rockies into
   the High Plains Wednesday afternoon/evening, as a midlevel shortwave
   trough traverses the region. Weak to moderate buoyancy and
   sufficient deep-layer shear will support a few organized
   cells/clusters capable of producing localized hail and severe gusts.

   ...Southeast AZ into southwest NM...
   Scattered thunderstorm development will again be possible across
   parts of southern AZ into southwest NM on Wednesday.
   Moisture/instability may be somewhat weaker than D1/Tuesday, though
   deep-layer shear will remain marginally sufficient for a few
   semi-organized storms. Depending on the extent of D1 convection
   across the region and its potential impact on D2 destabilization,
   severe probabilities may eventually be needed.

   ..Dean.. 09/12/2023

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