Mesoscale Discussion 0310
   NWS Storm Prediction Center Norman OK
   0146 PM CDT Wed Apr 08 2020

   Areas affected...souteast IA...northeast MO...and much of western
   and central IL

   Concerning...Severe potential...Watch likely 

   Valid 081846Z - 082045Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Thunderstorm development is expected in the next couple of
   hours near southeast IA/northeast MO/west-central IL. Very large
   hail and damaging winds will be the main threat associated with
   these storms.

   DISCUSSION...Strong heating across southeast IA into MO/IL ahead of
   a surface low and cold front has resulted in weak to moderate
   destabilization this afternoon. Strong boundary layer mixing has
   been noted across IL, where morning dewpoints had been in the mid
   50s F, generally are now in the mid 40s to low 50s F. Further south
   across MO toward southern IL, dewpoints from the low 60s to upper
   50s F were being maintained. Aloft, a plume of very steep midlevel
   lapse rates has continued to spread eastward across the mid-MS
   Valley, with 18z regional RAOBs showing 8-9 C/km lapse rates in
   place. Cumulus development near a quasi-stationary boundary from
   southeast IA into IL has been increasing, while additional deepening
   of midlevel CU near the MO/IA border continues. Stronger height
   falls have been noted recently across SD/NE into southern MN and
   western IA as a lead shortwave impulse begins to eject across the
   area ahead of the main upper trough. This is expected to provide
   adequate forcing for thunderstorm development in the next couple of
   hours. 

   Initial development is expected to be semi-discrete, higher-based
   supercells. Forecast hodographs continue to indicate long, straight
   hodographs with speed shear increasing with height. In conjunction
   with very steep lapse rates, large hail (some greater than 2 inches
   in diameter) is expected. Low level lapse rates also are steep
   across the region due to ample heating and mixing. This should act
   to enhance downdrafts, and damaging wind gusts also are expected. As
   frontal forcing increases later this evening, and through storm
   outflow interactions, upscale growth into one or more bowing
   segments is expected across parts of southeast MO into central IL,
   further enhancing the damaging wind threat. Given generally dry low
   levels resulting in higher-based storms, at least initially, the
   tornado threat is expected to be rather marginal.

   ..Leitman/Guyer.. 04/08/2020

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

   ATTN...WFO...LOT...ILX...LSX...DVN...SGF...DMX...EAX...

   LAT...LON   41029220 41159207 41289159 41359108 41259048 41128995
               40938931 40628849 40138781 39788757 39568758 39328769
               38838828 38358943 38019044 37879151 37949201 38459236
               39509241 40759227 41029220