SPC AC 201243

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0743 AM CDT Sat Jun 20 2020

   Valid 201300Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE GREAT
   PLAINS...

   ...SUMMARY...
   Scattered severe hail and damaging wind will be possible from
   eastern North Dakota to central Nebraska between about 2 to 10 PM
   CDT. Scattered large hail and severe wind gusts are also possible
   across parts of west Texas this afternoon into southern Oklahoma
   tonight.

   ...Dakotas/NE...
   Scattered thunderstorms are expected to develop by mid-afternoon
   along a surface trough from eastern ND to central SD and by early
   evening into central NE. While surface dew points should largely
   hold in the mid to upper 50s within a confined plume ahead of the
   trough, relatively cool mid-level temperatures associated with a
   Prairie Provinces to North-Central States shortwave trough should
   foster moderate buoyancy with MLCAPE reaching 1000-2000 J/kg.
   Effective shear of 25-35 kt (generally on the stronger side across
   NE/SD) will support multicell clusters and a few supercells with
   risks for severe hail and wind. The severe threat should become more
   marginal after dusk, owing to a lack of robust low-level mass
   response this evening.

   ...Southern Great Plains...
   Multiple areas of severe potential are evident during the period.
   The eastern corridor of severe potential should emanate near an MCV
   that should drift east across the Ark-La-Tex. Renewed storm
   development this afternoon is anticipated near and south of the MCV
   as weak to moderate buoyancy becomes prevalent. Damaging winds from
   wet microbursts within multicell clusters should be the primary
   hazard.

   With upper 60s surface dew points as far west as the Trans-Pecos,
   early afternoon storm development is anticipated over the higher
   terrain where strong instability and modestly favorable vertical
   shear should yield a few cells capable of large hail and severe
   wind. Farther north into the TX South Plains, a cluster of late
   afternoon/early evening storm development is possible near the lee
   trough/remnant outflow intersection. A separate area of storm
   development is expected later this evening north of the remnant
   outflow boundary near the Red River in southern OK as low-level warm
   advection strengthens. Convection should tend to cluster relatively
   quickly but large buoyancy and 30-35 kt effective shear should
   support a risk for large hail and severe wind amid initially modest
   MLCIN that would yield surface-based effective inflow parcels.

   ...Mid to Upper-MS Valley...
   A broad region from the mid-MS Valley into the Upper Midwest will
   become modestly unstable this afternoon, in advance of a
   weak surface front. Scattered thunderstorm development and/or
   intensification of lingering morning convection is possible after
   midday near the frontal boundary and in association with minor MCVs.
   Effective shear of 20-30 kt will support semi-organized multicell
   clusters, with an attendant risk of locally damaging wind and
   marginally severe hail.

   ...South Atlantic Coastal Plain...
   As an upper low slides southeast across eastern NC, a belt of
   enhanced mid-level northwesterlies around 25 kt should be centered
   on the Savannah Valley. Isolated to scattered thunderstorms are
   expected along the sea breeze with a few cells capable of locally
   damaging wind and marginally severe hail.

   ..Grams/Kerr.. 06/20/2020

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