SPC AC 211954

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0254 PM CDT Sun Jun 21 2020

   Valid 212000Z - 221200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM SOUTHWEST
   KANSAS INTO NORTHWEST OKLAHOMA...

   ...SUMMARY...
   Numerous severe storms are expected across the Plains, especially
   across southern/eastern Nebraska, western Iowa, and portions of
   Kansas and Oklahoma this afternoon and tonight. Very large hail,
   intense damaging wind gusts, and a few tornadoes will be possible.

   ...Discussion...

   Only modest adjustments have been made to previous forecast. Have
   expanded the MDT a bit south and east. A merger between storms
   developing over north central KS and those farther west along the
   front should occur by 21Z. Storms will subsequently develop south
   through western and south central KS and eventually into northern OK
   posing a risk for very large hail, and ultimately a more substantial
   wind threat should evolve as the MCS becomes better organized from
   southwest KS into northwest OK.

   ..Dial.. 06/21/2020

   .PREV DISCUSSION... /ISSUED 1157 AM CDT Sun Jun 21 2020/

   ...Central/Southern Plains...
   Severe thunderstorms are likely across the region, particularly late
   this afternoon and tonight across eastern/southern Nebraska, far
   western Iowa, and portions of Kansas/Oklahoma. 

   A slow-moving MCS continues to gradually decay across southern
   Oklahoma and north Texas, with this MCS having largely overturned
   the air mass across the middle part of Oklahoma/I-35 corridor
   vicinity. However, strong destabilization is expected especially on
   the western periphery of the MCS where outflow will continue to
   modify and the thicker cloud canopy will gradually thin. As sampled
   by 12Z observed soundings such as Amarillo/Dodge City, a plume of
   steep mid-level lapse rates will extend atop a moist boundary layer,
   with upwards of 3000-4500 J/kg MLCAPE expected by peak heating
   near/east of a surface low/triple point across west-central Kansas,
   southward into the eastern Texas Panhandle/western Oklahoma
   near/east of the dryline. Deep convective initiation may occur as
   early as mid-afternoon across west-central Kansas, with subsequent
   development expected across southwest Kansas and possibly the Texas
   Panhandle/Oklahoma border vicinity. Initial supercells capable of
   very large hail can be expected, along with some tornado risk.
   Storms are expected to gradually congeal/organize into a
   forward-propagating/southeastward-moving MCS this evening, with the
   greatest risk for a corridor of potentially widespread severe wind
   gusts (some significant 75+ mph) and wind-driven hail expected
   across southwest Kansas into northwest Oklahoma.

   Farther north, an isolated short-term severe threat may persist
   early this afternoon across north-central Kansas, but a more
   consequential severe risk should evolve later this afternoon. This
   convection across eastern/south-central Nebraska and north-central
   Kansas has complicated the scenario to a degree, but severe
   thunderstorm development is still expected later this afternoon,
   particularly where outflow intercepts the front across
   eastern/south-central Nebraska. Severe wind/hail are the primary
   hazards with some initial supercells likely evolving into
   southeastward-moving clusters this evening.

   ...ArkLaTex/Lower Mississippi Valley...
   Remnant MCS outflow/MCV may focus renewed severe thunderstorm
   development later this afternoon across the ArkLaTex and Lower
   Mississippi River Valley, with isolated damaging wind gusts and some
   severe hail a possibility.

   ...Ohio/Tennessee Valleys...
   An MCV over far western Kentucky will drift across the Ohio Valley
   today. Diabatic heating will be slowed near the MCV by relatively
   widespread early-day stratiform. Nevertheless, boundary-layer
   heating farther east and south of the morning precip may overlap
   with modest enhancement to mid-level flow to support multicell
   clustering. Isolated damaging winds should be the primary threat.

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