SPC AC 150559

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1259 AM CDT Sat Jun 15 2019

   Valid 151200Z - 161200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE CENTRAL AND SOUTHERN PLAINS INTO PORTIONS OF THE MIDWEST AND
   OHIO VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms are expected across portions of the
   central and southern Plains into parts of the Midwest and Ohio
   Valley later today into tonight.  The primary severe risks are wind
   and hail, though some tornado threat will also be present across
   portions of the Midwest.

   ...Southern MN...Eastern NE...IA...
   A vorticity maximum over the northern Great Plains this morning is
   forecast to move southeast across MN during the day. In conjunction
   with this feature, a weak surface low is forecast to move from
   eastern SD southeast into IA along a nearly stationary surface
   boundary. Scattered thunderstorm development is forecast by early
   afternoon in conjunction with these features across southern MN.
   Moderate instability (MLCAPE of 1500-2500 J/kg) and sufficient
   effective shear (25-35 kt) will support some organized structures,
   with organized multicell clusters and perhaps a supercell or two
   possible. Damaging wind gusts and possibly some hail will be the
   primary threats. While low-level flow/shear is expected to be rather
   weak, a brief tornado or two will be possible with any stronger cell
   interacting with the surface boundary. 

   ...Middle MS Valley into the OH Valley...
   Elevated convection will likely be ongoing at the start of the
   period across much of MO/IL, aided by a strong low-level jet and an
   MCV approaching from the west. While morning storms will likely be
   somewhat disorganized, some increase in convective intensity is
   possible in association with the MCV by afternoon from eastern IL
   into IN/western OH. Locally damaging winds would be the primary
   threat with any convection associated with the MCV, though low-level
   shear may be sufficient to support a risk of a tornado or two as
   well. 

   Meanwhile, thunderstorms may redevelop further west this afternoon
   along the trailing surface boundary/outflow from eastern MO into
   central IL. Along and south of the boundary, moderate
   destabilization is likely by afternoon, while moderate midlevel flow
   will support effective shear of 30-40 kt, sufficient for organized
   structures including some supercell potential. Damaging winds would
   be the primary threat with this activity, though some hail would
   also be possible. Low-level shear may also be sufficient to support
   a conditional tornado risk with any supercell interacting with the
   outflow boundary.

   Finally, later tonight, convection associated with a vorticity
   maximum moving southeastward across MN may move into this region
   before dissipating. Depending on the amount of instability remaining
   after earlier convection, some threat for strong wind gusts may
   persist into early Sunday morning. 

   ...Far northeast NM...West into North TX...OK...Southern KS...
   A low-amplitude midlevel trough is forecast to move from the
   southern Rockies into the southern Plains through the period. A
   surface boundary, reinforced by overnight convection, will likely be
   draped from the TX Panhandle or South Plains northeast into northern
   OK/southern KS, though some uncertainty remains regarding the
   boundary position by afternoon. A dryline will extend south into
   portions of west TX. Convective initiation is possible by late
   afternoon along the dryline, with an initial threat of large hail
   and locally severe wind gusts, given the presence of strong
   instability and steep low-level lapse rates. As the dryline storms
   move eastward into a modestly increasing low-level jet by early
   evening, some upscale growth is possible, though this scenario
   remains uncertain given increasing CINH with eastward extent. 

   Initiation further east along the surface boundary cannot be
   entirely ruled out during the day, but will become more likely this
   evening given the approach of the midlevel trough and increase in
   the low-level jet. Very strong buoyancy will develop along and south
   of the boundary, as dewpoints increase into the 68-72F beneath very
   steep midlevel lapse rates. Rather weak midlevel flow/effective
   shear may mitigate a more substantial severe threat, but given the
   degree of instability, any surface-based storms near the boundary,
   or slightly elevated storms north of the boundary, will be capable
   of producing large hail and severe wind gusts, and perhaps a brief
   tornado.

   ..Dean/Elliott.. 06/15/2019

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