SPC AC 171716

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1216 PM CDT Wed Apr 17 2024

   Valid 181200Z - 191200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
   EASTERN MISSOURI INTO SOUTHERN ILLINOIS...EXTREME SOUTHWEST
   INDIANA...FAR SOUTHWESTERN KENTUCKY...FAR NORTHWESTERN TENNESSEE...

   ...SUMMARY...
   Strong to severe storms capable of several damaging gusts, large
   hail, and perhaps a couple tornadoes, are likely tomorrow (Thursday)
   from parts of the lower Ohio Valley into the southern Plains.

   ...Synopsis...
   Mainly zonal flow aloft will overspread the CONUS tomorrow
   (Thursday) as a mid-level trough traverses the northern Plains. In
   response, a gradually weakening surface low will move from the
   central Plains toward the OH Valley as a surface cold front sags
   southward from the OH Valley to central TX through the day. Ample
   low-level moisture, overspread by cooler temperatures aloft, along
   with adequate deep-layer vertical wind shear, will precede the
   surface cold front and support a risk for severe thunderstorms by
   afternoon. Strong to severe thunderstorms will initiate off of the
   cold front by afternoon from the OH Valley into TX, with all severe
   hazards possible.

   ...MO into portions of the OH Valley...
   A surface low will be traversing central MO/IL during the late
   morning/afternoon hours, with thunderstorm development likely
   underway along the cold front at the start of the period. As the
   surface low continues to drift northeast, with the cold front
   drifting southeast, diurnal heating will destabilize the warm sector
   over the mid MS Valley, where an increase in convective coverage and
   intensity is expected. Here, surface temperatures will peak into the
   upper 70s to low 80s F amid mid 60s F dewpoints. 7-8 C/km mid-level
   lapse rates will overspread a deepening/mixing boundary layer,
   boosting SBCAPE into the 2000-3000 J/kg range. Deep-layer shear will
   not be overly strong, but modest mid-level flow and associated
   speed/directional shear will support low-level hodographs of modest
   curvature and limited mid-level elongation. This shear/buoyancy
   profile will support multicells (accompanied by wind and hail)
   rapidly growing upscale into a mature MCS by afternoon. Given a
   preceding mixed boundary layer, the MCS should efficiently produce
   damaging gusts, warranting the introduction of Category 3/Enhanced
   risk probabilities. Given modest low-level hodograph curvature,
   embedded mesovortices may develop near the apex of any bowing
   segments, perhaps accompanied by a QLCS tornado risk. 

   ...Portions of northern into central TX...
   Robust thunderstorm development should take place along/ahead of the
   southeastward-sagging cold front by afternoon peak heating. These
   storms will develop atop a well-mixed boundary layer, with 3000+
   J/kg SBCAPE expected to precede the storms given steep mid-level
   lapse rates overspreading upper 60s F surface dewpoints. Multicell
   thunderstorms, accompanied by a severe hail/wind risk, are expected
   given 30 kts of effective bulk shear and short hodographs over
   northern TX. Farther southwest into central TX though, locally
   stronger mid-level flow may support longer mid-level hodographs and
   9+ C/km mid-level lapse rates. These steeper lapse rates should
   result in deep, wide CAPE profiles, with a couple instances of 2+
   inch diameter hail possible, especially if more persistent updrafts
   can develop.

   ..Squitieri.. 04/17/2024

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