Mesoscale Discussion 1183
   NWS Storm Prediction Center Norman OK
   0936 AM CDT Sat Jul 11 2020

   Areas affected...East central Iowa into northern Illinois

   Concerning...Severe potential...Watch possible 

   Valid 111436Z - 111630Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Vigorous thunderstorm activity will probably pose a
   continuing risk for occasional severe hail and gusty winds another
   few hours.  There is potential for substantive further
   intensification, and a more sustained/widespread severe weather
   threat, by early afternoon.  Trends are being monitored for the
   possibility of a watch.

   DISCUSSION...Sustained ongoing convective development appears to be
   advecting  along a mid-level thermal gradient, parallel to the
   northwesterly flow regime on the northeastern periphery of prominent
   subtropical ridging.  Model output suggests that it is focused where
   forcing associated with lower/mid tropospheric warm advection is
   maximized, downstream of a significant short wave trough now digging
   across the eastern Dakotas.  This forcing will continue to shift
   southeastward toward the lower Ohio through this afternoon.

   Convection has been fluctuating in intensity, but appears supported
   by inflow of CAPE in excess of 1000 J/kg, and potentially up to
   2000-3000 J/kg, with moderate to strong shear in the convective
   layer.  Given ongoing moderate to strong boundary-layer
   destabilization to the south/southwest of the storms, there appears
   potential for storms to become increasingly rooted within the
   boundary layer, as associated convective outflow strengthens.  This
   probably would be accompanied by substantive further intensification
   and a tendency to propagate southward, as opposed to southeastward,
   across northwestern/central Illinois.

   ..Kerr/Guyer.. 07/11/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...ILX...DVN...ARX...DMX...

   LAT...LON   41359147 41869224 42229295 42739299 42909269 42889234
               42809173 42079008 41568965 40438908 39618974 40149056
               41359147