SPC AC 120555

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1155 PM CST Sun Nov 11 2018

   Valid 121200Z - 131200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF THE
   CENTRAL GULF COAST...

   ...SUMMARY...
   A few severe storms are possible on Monday across the central Gulf
   Coast, and across the coastal Carolinas Monday night.

   ...Synopsis...
   Deep, positively tilted upper trough is expected to move eastward
   throughout the period while amplifying. By 12Z Tuesday, this large
   upper troughing will likely feature more distinct northern and
   southern shortwave troughs than earlier in the period, with the
   northern shortwave centered over the upper Great Lakes and the
   southern shortwave extending from the Ozark Plateau into the TX Big
   Bend. Deep southwesterly flow will exist throughout the eastern
   periphery of the parent upper trough, gradually spreading eastward
   as the overall system shifts eastward and eventually extending over
   much of the eastern CONUS.

   Early period surface cyclone genesis is anticipated along the upper
   TX coast with the resulting surface low then tracking northeastward
   into central AL. Secondary surface cyclogenesis is anticipated over
   the Carolinas after 00Z Tuesday. Thunderstorms are possible in the
   vicinity of each of these lows, a few of which may be strong to
   severe.

   ...Central Gulf Coast...
   Strong moisture advection ahead of the approaching surface low will
   contribute to air mass destabilization across the region,
   particularly along the immediate coastal areas which are expected to
   be in the upper 60s to low 70s. Even so, limited insolation and poor
   lapse rates will result in generally moist, weakly unstable
   profiles. Strengthening southwesterly mid-level flow mentioned in
   the synopsis will be accompanied by a fairly robust low-level jet,
   resulting in moderate to strong deep-layer shear and long
   hodographs. Positive tilt to the upper trough and the resulting lack
   of stronger height falls will likely contribute to a fairly messy
   storm mode with weak but broad forcing for ascent across the warm
   sector. Given the potential for backed surface winds, the best
   chance for a low-topped supercell and brief tornado exists within
   any warm-sector confluence bands that develop ahead of the
   approaching surface low (and attendant cold front) during the early
   afternoon. Damaging wind gusts are also possible in this area as
   well as along the front where updraft intensification is possible as
   a result of cell mergers and/or frontal circulations.

   ...Coastal GA/Carolinas...
   There is a bit more uncertainty regarding how far inland the warm
   sector will develop across this region versus the central Gulf
   Coast, largely as a result of differences within the guidance on the
   location of surface cyclogenesis. Not only that, but significant air
   mass modification is needed to produce an environment supportive of
   thunderstorms. Highest likelihood is for this to occur along the
   coastal areas of GA, the Carolinas, and far southeast VA with a
   resulting potential in these areas for surface-based storms.
   Kinematic environment characterized by moderate to strong deep-layer
   shear and vertically veering low-level winds supports the potential
   for updraft rotation with the more persistent warm-sector storms.
   Corresponding threat for a brief tornado and/or damaging wind gusts
   is possible with any of these low-topped supercells.

   ..Mosier/Squitieri.. 11/12/2018

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