SPC AC 031236

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0736 AM CDT Tue Oct 03 2023

   Valid 031300Z - 041200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO EARLY TONIGHT FROM WESTERN/CENTRAL KS INTO SOUTH CENTRAL NE...

   ...SUMMARY...
   Isolated very large hail, occasional severe gusts and a few
   tornadoes will be possible this afternoon through early tonight
   across parts of the Great Plains.

   ...Synopsis...
   A surface cyclone in ND will develop northeastward today toward
   southeast SK/western ON as an associated/lead shortwave trough
   ejects northeastward over the northern Plains.  A trailing shortwave
   trough near the Four Corners will progress east-northeastward over
   the central Plains later this afternoon through early tonight, with
   weak lee cyclogenesis is expected near the CO/KS border today.  A
   surface cold front will move eastward/southeastward across the
   Dakotas, western NE and northeast CO this afternoon, in the wake of
   the ND cyclone (and north of the weak lee cyclone).  South of the
   weak lee cyclone, a dryline will mix eastward into southwest KS and
   the western TX Panhandle by mid afternoon.  The front and the
   dryline will help focus severe thunderstorm development, primarily
   this afternoon/evening from NE/KS into west TX.

   ...Central/southern Plains through tonight...
   A narrow corridor of low-mid 60s boundary-layer dewpoints will
   spread northward today to the east of a sharpening dryline, and in
   the wake of scattered morning convection that is ongoing from
   western KS to the TX South Plains.  Surface heating along the moist
   axis, beneath midlevel lapse rates greater than 7 C/km, will result
   in afternoon MLCAPE values of 1500-2500 J/kg with weakening
   convective inhibition.  Initial severe storm development may occur
   by about 20z across KS/NE, with subsequent expansion of the storms
   northeastward across NE toward southeast SD, with more scattered
   development southward along the dryline toward TX.  Long hodographs
   (effective bulk shear ranging from 45 kt across west TX to 65 kt
   closer to the KS/NE border) with the moderate buoyancy will favor
   supercells initially, with the potential to produce isolated very
   large hail up to 2.5 inches in diameter.  Some upscale growth into
   line segments is anticipated from northern KS into NE as storms
   align along the cold front.  The tornado threat will be modulated by
   rather modest hodograph curvature/SRH through much of the afternoon
   where the more discrete supercells are expected, and any evening
   increase in low-level shear will be somewhat countered by the
   tendency for more linear convective modes with northward extent.

   Farther south into west TX, weaker forcing for ascent suggests that
   storm coverage will be widely scattered along the dryline.  Still,
   there will be sufficient vertical shear/buoyancy for splitting
   supercells capable of producing large hail/isolated wind damage late
   this afternoon through late evening.

   ..Thompson.. 10/03/2023

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