SPC AC 040049

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0749 PM CDT Thu Oct 03 2024

   Valid 040100Z - 041200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TONIGHT ACROSS 
   PARTS OF SOUTHEASTERN IOWA...ADJACENT NORTHEASTERN MISSOURI AND WEST
   CENTRAL ILLINOIS...

   ...SUMMARY...
   An area of developing thunderstorms overnight may pose a risk for
   small to marginally severe hail across parts of southeastern Iowa,
   adjacent northeastern Missouri and west central Illinois.

   ...01Z Update...
   Within the mid-latitude westerlies, one notable short wave trough is
   forecast to continue digging across the northern Great Plains Red
   River Valley toward the upper Great Lakes region tonight.  The
   southern periphery of the surrounding cyclonic mid/upper-level flow
   currently curves across southern Nebraska through the Missouri/Iowa
   border vicinity, where it is beginning to overspread an initially
   quasi-stationary frontal zone.  Models suggest that this regime will
   become increasingly divergent late this evening into the overnight
   hours, contributing  to increasing forcing for ascent. 
   Lower/mid-level ascent is already increasing  across Iowa and
   surrounding portions of the Missouri Valley/Upper Midwest, in
   response to warm advection.  It appears that this will lead to
   increasing thunderstorm development by 05-07Z across parts of
   central/southern Iowa, where guidance indicates a corridor of modest
   destabilization is possible associated with weak elevated moisture
   return above the frontal zone.

   Forecast soundings indicate most unstable CAPE may increase in
   excess of 1000 J/kg along this corridor, in the presence of modest
   potential cloud-bearing layer shear.  Thermodynamic profiles may
   include sufficiently cool mid-levels (and steep lapse rates) to
   support a risk for marginally severe hail (up to around 1 inch or so
   in diameter) in a few of the stronger storms.

   ..Kerr.. 10/04/2024

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