SPC AC 200532

   Day 2 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   1232 AM CDT Wed May 20 2020

   Valid 211200Z - 221200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THURSDAY
   AFTERNOON AND EVENING ACROSS PARTS OF SOUTHEASTERN
   COLORADO...SOUTHWESTERN KANSAS...NORTHWESTERN OKLAHOMA AND
   NORTHEASTERN PORTIONS OF THE TEXAS PANHANDLE...

   CORRECTED FOR NDFD AND WIND PROBABILITY GRAPHIC

   ...SUMMARY...
   Thunderstorms may develop and evolve into an organizing cluster
   across central portions of the higher Plains late Thursday afternoon
   and evening, accompanied by a risk for severe hail and strong wind
   gusts.

   ...Synopsis...
   It still appears that blocking within the mid/upper flow east of the
   Plains may undergo more substantive weakening Thursday through
   Thursday night.  This is expected to occur as a vigorous short wave
   impulse digs southeast of Hudson Bay, toward Newfoundland and
   Labrador, and contributes to substantive weakening of mid-level
   ridging initially extending across the upper through lower Great
   Lakes region.  Additionally, large-scale western U.S. troughing is
   generally forecast to develop eastward across the northern and
   central Plains, toward the upper Mississippi Valley, and may
   contribute to some net northward motion of the remnant cut-off low
   toward the middle Ohio Valley.

   Within the Western large-scale troughing, the bulk of a significant
   initial perturbation emerging from the Intermountain West is
   forecast to pivot north-northwestward across the international
   border.  An embedded mid-level low may eventually evolve by the end
   of the period across Alberta, to the north of another significant
   short wave trough digging southeast of the Pacific Northwest coast
   into the northern intermountain region.  At the same time, another
   portion of the lead perturbation may become increasingly sheared
   while accelerating north-northeastward across the northern Plains,
   and remnant troughing emerging from the Four Corners/Colorado Valley
   vicinity may accelerate into the central Plains.  However, spread
   among the various model output appears largest with these latter
   developments.

   In lower levels, the primary surface cyclone is forecast to migrate
   northward away from the international border, through Saskatchewan,
   with surface troughing lingering across the western Dakotas into the
   immediate lee of the Front Range of the Rockies Thursday afternoon. 
   Southeast of the Front Range, a remnant frontal zone may strengthen
   during the day across southeastern Colorado, southwestern Kansas and
   the Oklahoma/Texas Panhandle vicinity, while a dryline sharpens
   across the Texas South Plains into the Texas Big Bend vicinity. 
   These features may become the focus for modest to strong
   boundary-layer destabilization in the presence of at least moderate
   deep-layer shear, providing potential for isolated to widely
   scattered strong to severe storm development Thursday afternoon and
   evening.

   ...Central High Plains...
   Beneath a remnant plume of warm elevated-mixed layer air, strong
   boundary layer heating to the lee of the Rockies will contribute to
   a strengthening baroclinic zone associated with differential
   heating.  Moist southeasterly to northerly flow along this zone may
   contribute to mixed-layer CAPE of 1000-2000+ J/kg by late afternoon,
   providing support for thunderstorm development as inhibition weakens
   with cooling aloft.  This may initiate in low-level upslope flow
   east/northeast of the Raton Mesa vicinity, before increasing and
   possibly consolidating within strengthening low-level warm
   advection. An evolving cluster of storms may gradually organize,
   particularly by early evening, aided by a modest strengthening
   low-level jet (30-40 kt).  This could be accompanied by increasing
   potential for severe wind gusts, in addition to large hail, before
   convection weakens while spreading east-southeastward overnight.

   ...Eastern South Carolina/southeastern North Carolina...
   It appears that moderate CAPE (1000-2000 J/kg) could develop in
   association with seasonably high boundary-layer moisture content,
   near a wave along a remnant frontal.  In the presence of weak to,
   perhaps, modest shear, focused low-level convergence could support a
   clustering of storms with potential to produce strong wind gusts,
   associated with heavy precipitation loading in downdrafts, and along
   possible consolidating cold pools.

   ..Kerr.. 05/20/2020

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