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 continues. 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 required. 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 www.spc.noaa.gov for graphic product... ATTN...WFO...DVN...DMX...EAX...OAX... LAT...LON 41409669 41969684 42039287 42289157 41399154 40709243 40359580 40559682 41409669