ZCZC SPCSWOMCD ALL ACUS11 KWNS 160647 SPC MCD 160647 IAZ000-160815- Mesoscale Discussion 1287 NWS Storm Prediction Center Norman OK 0147 AM CDT Sun Jun 16 2024 Areas affected...portions of IA Concerning...Severe Thunderstorm Watch 421... Valid 160647Z - 160815Z The severe weather threat for Severe Thunderstorm Watch 421 continues. SUMMARY...Isolated thunderstorms may sporadically produce hail the next couple hours. DISCUSSION...Thunderstorms on the back side of an MCV over western/central IA have occasionally intensified the past hour or so. Midlevel lapse rates will remain weak over the area due to earlier convection. However, sufficient instability is present on the periphery of the MCV, along with enhanced vertical shear, to sustain briefly strong storms. As convection develops east/northeast, overall weakening is expected as the airmass becomes less favorable for severe storms. A new watch is not expected, and WW 421 will expire at 07z. ..Leitman.. 06/16/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...FSD...OAX... LAT...LON 42019570 42469571 42779548 42999492 42869394 42519324 42029304 41539291 41289316 41379404 41569479 41949567 42019570 NNNN