SPC AC 031940

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0240 PM CDT Mon May 03 2021

   Valid 032000Z - 041200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
   TX AND SOUTHEAST OK INTO THE MID-MS VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHEAST...

   ...SUMMARY...
   The greatest severe-thunderstorm threat appears to be from late
   afternoon through tonight in a corridor from northeast Texas and
   southeast Oklahoma to the Lower Ohio Valley. Very large hail,
   tornadoes (a couple of which may be significant), and intense
   damaging winds are expected.

   ...20z Update...

   Only minor adjustments have been made to the convective outlook with
   the 20z update. The main change is to trim the Marginal and Slight
   risk areas across parts of IA/MO based on the current location of
   the surface cold front and ongoing/developing convection. Other
   minor adjustments have been made to the Slight risk area across
   parts of upstate SC into central NC based on current observations
   and radar trends. Otherwise, the forecast philosophy remains
   unchanged from the previous outlook. See below for the previous
   discussion, and reference MCDs 494, 495, 496, and 497 for near-term
   details/expectations.

   ..Leitman.. 05/03/2021

   .PREV DISCUSSION... /ISSUED 1123 AM CDT Mon May 03 2021/

   ...Southern Great Plains to Mid-South...
   Two primary corridors of severe thunderstorms are expected to
   develop by late afternoon. The first within a post-frontal regime
   off the higher terrain of NM spreading east across the TX South
   Plains towards the Big Country and western north TX. Very steep
   mid-level lapse rates in conjunction with robust speed shear in the
   mid-upper portion of the thermodynamic profile should prove
   favorable for a long-track supercell or two with a primary hazard of
   large to significant severe hail. 

   The second area of severe thunderstorms will rapidly develop along
   the dryline to surface front intersection across central TX before
   spreading into southeast OK. Large buoyancy given the very steep
   mid-level lapse rates will support intense supercells capable of all
   hazards, some of which will be significant. Guidance still differs
   on the degree of low-level flow response this evening rendering
   uncertainty over how long discrete supercells will be maintained.
   Given rich boundary-layer moisture coupled with the large MLCAPE,
   there is concern for at least conditional significant tornado
   potential across a portion of north TX into southeast OK. If upscale
   growth occurs too quickly, this may not be realized, but have
   highlighted a corridor of enhanced tornado potential in this region.
   Otherwise, upscale growth will occur at some point this evening
   rendering a predominant severe wind threat spreading east-northeast
   towards the Mid-South through tonight.

   ...Southeast...
   Scattered thunderstorms will persist across a broad swath of the
   southeast states through this evening. A shortwave trough over the
   OH Valley will move east with the belt of stronger low/mid-level
   flow to its southeast focused across the Carolinas and VA. Along the
   periphery of moderate buoyancy, the threat for a few tornadoes and
   scattered damaging winds should develop from GA to southeast VA. 

   Farther west, low-level flow will become increasingly veered and
   slowly subside through the afternoon. However, larger buoyancy along
   the eastern periphery of the EML emanating east from the
   south-central states will maintain a threat for scattered damaging
   winds and large hail.

   ...Midwest...
   An MCV over northeast MO will be the primary mechanism for scattered
   thunderstorm development across the Mid-MS Valley into IL late
   today. Abundant cloud coverage downstream should delay the severe
   storm threat until at least late afternoon. An additional swath of
   severe storm development is anticipated along the cold front in MO
   where more robust boundary-layer heating is underway. This activity
   will likely grow upscale into an east-southeast moving MCS towards
   the Lower OH Valley region this evening with damaging winds becoming
   the primary hazard.

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