SPC AC 021728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Sun May 02 2021

   Valid 031200Z - 041200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
   EASTERN OKLAHOMA AND FAR NORTHEAST TEXAS INTO THE MIDDLE MISSISSIPPI
   AND LOWER OHIO VALLEYS...

   ...SUMMARY...
   Severe thunderstorms are expected across parts of Oklahoma and far
   northeast Texas into the middle Mississippi and lower Ohio Valleys
   on Monday. Damaging gusts, large hail and a few tornadoes will be
   possible with this activity. Additional strong to isolated severe
   thunderstorms are possible from the southern Plains into portions of
   the Southeast and Mid-Atlantic.

   ...Synopsis...

   An active severe weather day is expected on Monday from portions of
   the southern Plains through the Ohio Valley and into portions of the
   Southeast/Mid-Atlantic vicinity. A weak shortwave impulse will be
   oriented near Lake Michigan toward AL/GA during the morning, and
   lift northeast to the Northeast/Mid-Atlantic coastal vicinity by the
   end of the period. A belt of enhanced southwesterly midlevel flow
   associated with this feature will overspread portions of the TN
   Valley to the Mid-Atlantic atop a moist boundary layer and modest
   lapse rate environment. This should support scattered thunderstorm
   development across much of the southern/central Appalachians into
   the VA/NC Piedmont and Chesapeake Bay vicinity through Monday
   evening. 

   To the west, a deep mid/upper trough will eject from the Rockies and
   across the Plains toward the MS Valley vicinity during the forecast
   period. A plume of steep midlevel lapse rates will overspread the
   southern Plains and mid-MS/lower OH Valleys ahead of a cold front
   and atop a seasonally moist boundary layer. Severe thunderstorms are
   expected near/ahead of the front from the southern Plains into the
   Ohio Valley through Monday night/early Tuesday morning. Some of
   these storms could produce very large hail, significant wind damage
   and a few tornadoes.

   ...OK/TX to the Lower OH Valley...

   A cold front will extend from a surface low over western IA to a
   surface low over northwest TX Monday morning, while a dryline
   extends southward across northern into central TX. Ahead of these
   features, dewpoints in the 60s will exist, with mid/upper 60s
   dewpoints possible as far north as central IL, and low 70s dewpoints
   from the Arklatex toward the MO bootheel, by Monday evening. A plume
   of steep midlevel lapse rates around 7.5-8.5 C/km atop this moist
   boundary layer will aid in moderate to strong destabilization with
   MLCAPE values from 1500-3000 J/kg expected. The strongest
   instability/steepest lapse rate corridor is expected across parts of
   northern AR into far southern MO east/northeast to southern
   IN/western KY. 

   Isolated strong to severe thunderstorms may be ongoing ahead of the
   front across eastern IA during the morning. Convection should
   increase and intensify as it shifts east into northern IL through
   the afternoon. Hail and locally damaging gusts will be possible with
   this activity. Convection will develop during the late afternoon
   into the evening hours further south/southwest as upper trough
   ejects into the Plains and the cold front surges east/southeast from
   portions of central MO/IL into southwest OK/northwest TX. This
   activity will develop amid supercell wind profiles and initial
   cellular activity could produce very large hail, damaging gusts and
   a few tornadoes, especially across northern AR/southern MO toward
   southern IL/western KY. Convection may grow upscale late Monday
   night into early Tuesday morning across southeast MO/southern IL and
   spread eastward into the lower OH Valley with a continued damaging
   wind and tornado threat.

   ...Southwest OK/Northwest TX...

   Isolated thunderstorms are expected to develop near or behind the
   cold front from late afternoon into the evening. This activity will
   be elevated, but moderate instability and very steep lapse rates
   amid strong shear will support large hail potential. Depending on
   model trends, Slight risk probabilities may need to be expanded
   across this area in later outlooks for SIG hail potential.

   ...Southeast to Mid-Atlantic vicinity...

   While the midlevel shortwave trough will lift northeast of the
   southern Appalachians during the morning hours, a belt of 35-45 kt
   850-700 mb flow will overspread much of the Southeast to
   Mid-Atlantic vicinity. A seasonally warm and moist boundary layer
   will be in place, and scattered thunderstorm development is expected
   during the morning into the afternoon/evening. Slightly increasing
   mid/upper level heights may suppress stronger convection across
   parts of AL/GA, but even pulse-like convection could produce
   sporadic damaging gusts or hail. Further north across the central
   Appalachians/Mid-Atlantic, moderate shear and instability will
   support isolated strong to severe thunderstorms, mainly capable of
   strong gusts and hail.

   ..Leitman.. 05/02/2021

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