Mesoscale Discussion 0767 NWS Storm Prediction Center Norman OK 0124 AM CDT Mon May 18 2026 Areas affected...eastern Iowa and far southwestern Wisconsin Concerning...Severe Thunderstorm Watch 219... Valid 180624Z - 180800Z The severe weather threat for Severe Thunderstorm Watch 219 continues. SUMMARY...An overall weakening trend is expected to continue with the thunderstorm complex across Iowa. If this trend continues, the severe thunderstorm watch may need to be canceled early. DISCUSSION...A formerly well organized MCS continues to move east across Iowa this morning. The environment ahead of the MCS remains quite unstable with objective analysis suggesting greater than 2000 J/kg of MUCAPE remains. Additionally, VAD profile winds from Davenport, IA, indicates strong low-level curvature within the lowest 1-km leading to 0-1km SRH in excess of 700 m2/s2 (as compared to ~300 m2/s2 on objective analyses). However, effective-layer shear decreases markedly across Iowa from west-to-east, with less than 30 knots along and ahead of the ongoing MCS. Radar observations show the effects of this as regional radar depicts a weakening MCS with a gust front pushing ahead of the main convection. Additionally, MRMS CAPPI products depict a weakening trend even within the strongest updraft cores. Given the observational trends and that the MCS continues to move farther away from the better upper-level support, this weakening trend is expected to continue through the morning. An isolated severe hail or wind report cannot be ruled out in the near term, however, the overall trend may support canceling Severe Thunderstorm Watch #219 early. ..Marsh.. 05/18/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MKX...DVN...ARX...DMX... LAT...LON 40619304 41299269 41679260 41989179 42509132 43169096 43699091 43729031 43269012 42349053 41539097 40639168 40619304 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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