SPC AC 230513

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1213 AM CDT Tue Apr 23 2024

   Valid 231200Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   NORTHWEST TEXAS...

   ...SUMMARY...
   A few severe thunderstorms capable of producing large hail (2+ inch
   diameter) and gusts to 65 mph will be possible this afternoon and
   evening across northwest Texas. Additional strong storms producing
   hail to near 1 inch diameter and 60 mph gusts are possible from
   southeast Wisconsin and northern Illinois into Lower Michigan.

   ...Synopsis...

   An upper shortwave trough will pivot eastward across the Upper Great
   Lakes to the Northeast today. Meanwhile, upper ridging will be
   focused over the Rockies. At the surface, an area of elongated low
   pressure is forecast from Quebec to the Upper MS Valley. A secondary
   surface low is forecast to develop over the TX Panhandle/South
   Plains. A cold front will link between these two areas of low
   pressure, extending from southwest WI to central OK and the TX
   Panhandle by early/mid afternoon. A prior cold frontal intrusion
   into the Gulf of Mexico and surface high pressure over the Southeast
   will limit boundary-layer moisture. However, east/southeasterly
   low-level trajectories into TX become more south/southwest into OK
   and the along the surface trough into the Upper Great Lakes will
   allow for low 60s F dewpoints south (southern Plains) to 40s F
   dewpoints north (Great Lakes).

   ...Upper Great Lakes...

   Stronger large-scale ascent will be focused across WI/Lower MI and
   vicinity during the afternoon ahead of the surface front and upper
   shortwave trough. While boundary-layer moisture will remain modest,
   temperatures aloft are forecast to be quite cool, resulting in very
   steep midlevel lapse rates. This will foster MLCAPE values generally
   less than 750 J/kg amid modest effective shear magnitudes greater
   than 30 kt. This should support isolated strong to severe storms
   during the afternoon/evening from southeast WI into northern IL/IN
   and parts of Lower MI. Elongated hodographs and mainly elevated
   instability coupled with the cold temperatures aloft may support
   hail to near 1 inch diameter. Steep low-level lapse rates amid a dry
   boundary-layer also may support locally strong gusts. 

   ...Northwest TX/Southwest OK vicinity...

   Large-scale ascent will be somewhat nebulous over the region today,
   but subtle northwest flow aloft amid veering low-level wind profiles
   will result in 40+ kt effective shear magnitudes. Strong heating in
   the vicinity of a surface low/triple point and dryline, coupled with
   steep midlevel lapse rates, will aid in moderate destabilization
   (MLCAPE around 1500-2000 J/kg possible). This should support a few
   organized cells during the late afternoon/evening. Elongated
   forecast hodographs and modest vertical shear through 3 km suggests
   supercells capable of large hail (2+ inch diameter) are possible.
   Weak low-level flow and mixing to around 850 mb also indicates some
   potential for locally strong/severe gusts. While storm coverage is
   expected to remain isolated, given potential for significant hail
   (2+ inch diameter), a Slight (level 2 of 5) risk has been included.

   ..Leitman/Weinman.. 04/23/2024

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