Mesoscale Discussion 1089
   NWS Storm Prediction Center Norman OK
   0518 PM CDT Thu Jul 19 2018

   Areas affected...Eastern Iowa into far northeast Missouri and
   northwestern Illinois.

   Concerning...Tornado Watch 285...

   Valid 192218Z - 192315Z

   The severe weather threat for Tornado Watch 285 continues.

   SUMMARY...Several tornadoes have been confirmed from two supercells
   in east central Iowa. The tornado threat continues into the evening
   across the eastern half of tornado watch 285.

   DISCUSSION...Two supercells have generated numerous confirmed
   tornadoes across central and east central Iowa this evening. The
   tornado confirmed in Marshalltown, Iowa formed as the northern
   supercell interacted with the outflow boundary from the southern
   supercell. This supercell has now weakened significantly as it moved
   into a cooler airmass east of this outflow boundary. A tornado
   threat continues across the entire watch area, but the highest
   tornado threat is now associated with the supercell moving into
   Keokuk and Wapello counties where instability is maximized with
   MLCAPE around 2500 J/kg. Will be watching these storms for upscale
   growth over the next hour or two as some CAMS suggest these storms
   may congeal and pose a wind threat into northwest Illinois later
   this evening.

   ..Bentley.. 07/19/2018

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

   ATTN...WFO...ILX...DVN...DMX...EAX...

   LAT...LON   42449371 42579354 42559263 42409201 42269103 42069040
               41749007 41199018 40219050 40319172 40349226 40569299
               40709333 41699354 42449371