SPC AC 241742

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1242 PM CDT Fri Jul 24 2020

   Valid 251200Z - 261200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF THE NORTHERN AND CENTRAL PLAINS AND THE UPPER MIDWEST AS WELL AS
   SOUTH TEXAS...

   ...SUMMARY...
   Strong thunderstorms may impact parts of the Upper Midwest and
   northern Plains Saturday into Saturday night, accompanied by some
   risk for severe weather.  Meanwhile, developing Tropical Storm Hanna
   may pose some risk for a couple of tornadoes across south Texas as
   it move inland later Saturday afternoon into Saturday night.

   ...Northern Plains into the Upper Midwest regions...

   A shortwave trough situated over the central Rockies will advance
   northeast and move through the upper MS Valley Saturday morning and
   early afternoon. In wake of this feature a northern-stream trough
   will advance east along the international border and begin to affect
   western ND later Saturday afternoon. A cold front will move through
   the western Dakotas Saturday morning and by early afternoon should
   extend from central ND through western SD and into eastern WY. This
   feature will be preceded by pre-frontal trough that will stretch
   from central SD through western NE into northeast CO. 

   Current indications are that widespread showers and thunderstorms
   will be ongoing across the upper MS Valley region in association
   with the lead shortwave trough and its attendant low-level jet.
   While vertical shear profiles including larger 0-1 km hodographs
   accompanying this feature will be sufficient for a severe threat,
   the overall severe potential will probably be mitigated by limited
   destabilization. Nevertheless, given the moist surface layer with
   dewpoints around 70 F, storms will likely be surface based, and a
   few strong gusts and perhaps a tornado cannot be ruled out. 

   Upstream of the morning storms across the Dakotas and farther south
   into NE, the atmosphere will likely become moderately unstable with 
   2000-3000 J/kg MLCAPE supported by diabatic warming of the moist
   surface layer. A few thunderstorms are expected to develop along the
   cold front across ND during the afternoon, and this region will
   reside within belt of stronger mid-upper flow accompanying the
   approaching shortwave trough supporting 30-40 kt effective bulk
   shear. However flow through the lowest 3 km will remain relatively
   weak and the deeper forcing will likely remain north of the
   international border. Nevertheless, this parameter space will
   support potential for a few supercells and multicells capable of
   isolated large hail and a few locally strong to damaging gusts. This
   area might need to be upgraded to a SLGT risk in day 1 updates.

   Farther south additional storms will likely develop across NE along
   pre-frontal trough within the weakly sheared, but moderately 
   unstable environment. Isolated downburst winds and hail will be the
   main threats.  

   ...South Texas...

   At least a low-end threat for a couple of tornadoes will exist
   across south TX Saturday afternoon into the overnight near and after
   tropical storm Hanna makes landfall.

   ..Dial.. 07/24/2020

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