US Mesoscale Discussions

Storm Prediction Center Mesoscale Discussion 867

   Mesoscale Discussion 0867
   NWS Storm Prediction Center Norman OK
   0551 AM CDT Tue May 21 2024

   Areas affected...eastern Nebraska eastward across southwestern and
   south-central Iowa

   Concerning...Severe Thunderstorm Watch 274...

   Valid 211051Z - 211245Z

   The severe weather threat for Severe Thunderstorm Watch 274

   SUMMARY...Severe risk -- mainly in the form of locally damaging wind
   gusts -- will continue spreading eastward across eastern Nebraska
   and into southwestern Iowa over the next couple of hours.  New WW
   issuance across southwestern and south-central Iowa will likely be

   DISCUSSION...Latest radar loop shows an organized/bowing north-south
   band of storms moving quickly eastward across eastern Nebraska at
   around 50 kt.  Meanwhile, a more-loosely organized, west-to-east
   band of convection, on the cool side of a front/outflow composite
   boundary lying west-to-east across central portions of Iowa,
   continues to make slow southward progress.  North of this
   west-to-east convective band, widespread rain has substantially
   stabilized the lowest levels of the troposphere, with temperatures
   in the low 60s and dewpoints near 60 across central and northern
   Iowa.  As such, little potential for surface-based severe weather
   appears to exist north of this convective band.  As the northern
   portion of the strong/severe convective arc over eastern Nebraska
   continues moving northeastward, eventually shifting atop this cooler
   air, weakening of this convection  -- at least in terms of severe
   risk -- is anticipated.

   With that said, portions of the Nebraska bow moving more eastward
   toward the Omaha area and areas south, will remain near/south of the
   west-to-east Iowa surface boundary.  It is across this corridor --
   i.e. roughly the southern third of Iowa -- where severe risk is
   expected to persist longer into the morning hours.  As storms
   approach eastern fringes of WW 274, a new WW will likely therefore
   be required across southern Iowa.

   ..Goss.. 05/21/2024

   ...Please see for graphic product...


   LAT...LON   41409669 41969684 42039287 42289157 41399154 40709243
               40359580 40559682 41409669 

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