SPC AC 030538

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1238 AM CDT Thu Sep 03 2020

   Valid 031200Z - 041200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MIDDLE ATLANTIC...

   ...SUMMARY...
   Scattered severe thunderstorms appear likely across parts of the
   Mid-Atlantic on Thursday. Damaging wind gusts and a few tornadoes
   should be the main threats.

   ...Middle Atlantic...

   Latest water-vapor imagery depicts a strong upper trough over
   southwestern MB/eastern ND, digging southeast line with latest model
   guidance. Height falls ahead of this feature should encourage a
   notable short-wave trough over the Mid-South to eject northeast
   before approaching the Middle Atlantic by early afternoon. At
   03/0530z, radar data exhibited a small cluster of thunderstorms
   immediately ahead of the southern short wave near the KY/TN border.
   This activity should advance across the TN Valley into WV early in
   the period before appreciable surface heating enhances buoyancy
   downstream. It appears the greatest corridor of steep low-level
   lapse rates should be in the lee of the central Appalachians from VA
   into southern NJ where temperatures should rise into the upper
   80s-90F. 00z NAM suggests a 50kt 500mb speed max will translate
   across WV by 18z, then off the NJ coast by 04/00z.

   Latest thinking is scattered deep convection should begin to
   intensify ahead of the short wave by late morning across the higher
   terrain of the central Appalachians, then spread/develop east toward
   the Delmarva within a plume of high-PW air (2+ inches). While
   mid-level lapse rates will necessarily be modest due to the abundant
   PW, robust updrafts are expected given the shear/buoyancy. Forecast
   soundings suggest discrete supercells are possible and latest CAMs
   support this scenario. Earlier thoughts regarding the prospect for a
   corridor of enhanced robust convection continue. While a few
   tornadoes are certainly possible, the primary threat should be
   damaging winds, especially if bow-type structures ultimately evolve.

   ...Lower MI...

   Strong short-wave trough will dig southeast across the Great Lakes
   during the day as 90kt mid-level speed max translates across WI into
   northern Lower MI. While forecast instability will not be that
   significant, soundings across lower MI suggest convection should
   easily develop along a strongly forced surface front. Gusty winds
   will likely be noted with this diurnally enhanced convection.

   ...South-Central TX...

   A weakness in the mid-level height field will become detached from
   stronger flow aloft over central TX later this morning. This feature
   should drift south during the day encouraging the primary zone of
   low-level convergence to sag into south-central TX. Strong diurnal
   heating is expected to aid buoyancy for at least isolated robust
   convection. Gusty winds should be the primary threat with storms
   that propagate south across this region.

   ..Darrow/Lyons.. 09/03/2020

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z