SPC AC 230547

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1247 AM CDT Sat May 23 2020

   Valid 241200Z - 251200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE MIDDLE MO VALLEY...CENTRAL PLAINS...AND SOUTHERN HIGH PLAINS...

   ...SUMMARY...
   Severe thunderstorms are possible across portions of the central
   Plains, Middle Missouri Valley, and southern High Plains on Sunday.
   Large hail and damaging wind gusts are the primary severe threats.

   ...Synopsis...
   A broad upper trough is forecast to cover much of the western CONUS
   early Sunday morning. Gradual eastward progression of this trough is
   anticipated throughout the day, with its eastern periphery extending
   through the Plains by early Monday morning. Several shortwave
   troughs will rotate through this trough, including one from the
   southern High Plains into the southern Plains and another from the
   northern Great Basin through the Four Corners. 

   Surface pattern early Sunday morning will likely feature a broad
   area of low pressure from the southern High Plains into eastern
   portions of the northern Plains. Several lows will be embedded
   within this area, including one centered near the eastern NE/SD
   border. A warm front will extend southeastward from this low through
   central IA and into northern IL, while a cold front extends
   southwestward to another low near the OK/KS/CO border intersection.
   As the upper trough moves eastward, the warm front is forecast to
   move northward into the Upper Midwest, while the cold front moves
   eastward across the central Plains and middle MO Valley. Portions of
   the front in the vicinity of the southernmost low are expected to
   remain stationary while the dryline pushes eastward across the TX
   Panhandle/southwest TX. A warm and unstable warm sector will be in
   place ahead of the front and dryline, which is expected to result in
   widespread thunderstorms, some severe, as the front moves eastward.

   ...Central Plains into the Mid MO/Mid MS Valleys...
   Showers and thunderstorms will likely be ongoing across the Mid MO
   Valley early Sunday morning, supported by warm-air advection and
   steep mid-level lapse rates. Vertical shear and instability are
   strong enough to support isolated severe hail with these storms.

   Thereafter, strong heating amidst abundant low-level moisture (i.e.
   dewpoints in the upper 60s/low 70s) will contribute to very strong
   instability. Current guidance suggests 3000-4000 J/kg of MLCAPE is
   possible from central KS into central IA, with little to no
   convective inhibition by the late afternoon. Large-scale forcing for
   ascent will be weak but convective initiation is still anticipated
   via convergence along the front. Surface low over IA could lead to
   slightly stronger convergence and higher potential for convective
   initiation. Backed surface flow may also contribute to relatively
   higher tornado potential. The better flow aloft and vertical shear
   will be displaced northwest of the strongest instability but any
   storms that form should develop strong updrafts via buoyancy alone.
   Hail will be the primary threat with initial development but then
   transitioning to damaging wind gusts. 

   In areas where daytime development does not occur, evening storms
   are possible amidst a strengthening low-level jet. Once again, the
   primary severe threat will be hail.

   ...Southern High Plains...
   Strong instability will develop ahead of the dryline amidst robust
   heating and deep boundary-layer mixing. Convergence along the
   dryline will be augmented by ascent attendant to an approaching
   shortwave trough and the right-entrance region to an upper jet.
   Consequently, storm development appears probable along the length of
   the dryline. Vertical shear will be weak but strong instability will
   still support large hail and/or damaging wind gusts. 

   ...TX Hill Country into South TX/Rio Grande Valley ...
   Model guidance suggests the southern periphery of the southern High
   Plains shortwave trough will extend far enough south to aid in storm
   development across the high terrain of northwest Mexico, with those
   storms then moving into adjacent portions of the TX Hill Country and
   the Rio Grande Valley. Potential exists for the development of an
   organized convective line, and higher severe probabilities may be
   needed in later outlooks if confidence in this scenario increases.

   ...Southeast/East TX into western LA...
   Presence of a mesoscale convective vortex from antecedent storms
   appears likely over the middle TX coast Sunday morning.
   Thunderstorms are anticipated across southeast/east TX and into
   western LA as this vortex drifts northeastward throughout the day.
   Enhanced flow aloft surrounding this system could contribute to
   locally strong vertical shear and a few more organized storms.
   Damaging wind gusts and perhaps even a brief tornado are possible.

   ..Mosier.. 05/23/2020

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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z