Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 17 2025 12:42:56 ACUS01 KWNS 171242 SWODY1 SPC AC 171241 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0741 AM CDT Thu Apr 17 2025 Valid 171300Z - 181200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO EARLY TONIGHT FROM EASTERN NEBRASKA INTO WESTERN AND CENTRAL IOWA... ....SUMMARY... Isolated to scattered severe thunderstorms are expected, mainly from late afternoon into early tonight from eastern Nebraska into western and central Iowa. Very large hail to 3 inches in diameter or greater, isolated severe gusts of 60-70 mph, and a couple of tornadoes will all be possible. ....NE/IA/MN/MO through early tonight... Southwest mid-upper flow will persist through the period from the southern High Plains to the central Plains and upper MS Valley, downstream from a large-scale, positive-tilt trough from MB to the Great Basin. A weak surface wave is expected to move along an associated baroclinic from the mid MO Valley to the upper MS Valley, while a lee cyclone develops south-southeastward across the central High Plains. A modifying Gulf air mass (boundary-layer dewpoints in the mid 50s to low 60s) will continue to spread northward in the warm sector from the southern Plains to eastern KS, IA and southern MN, beneath the eastern extent of a relatively warm EML. A cluster of elevated storms, with embedded supercell structures, is ongoing over southwest MO. These storms are expected to weaken this morning as the low-level jet and associated warm advection diminish, coincident with the eastward expansion of the EML. In the interim, isolated large hail (around 1 inch diameter) and strong gusts (50-60 mph) will be possible for a couple of hours this morning across southwest MO. In the wake of the morning convection, surface heating and continued moisture advection will result in steady destabilization from eastern KS to eastern NE/western IA and southern MN. Thunderstorm development is expected near 20z into southern MN where the cap will be a little weaker, and after about 22z in eastern NE (near and just east of the cold front/dryline triple point). The storm environment into southern MN will favor a mix of supercells and storm clusters capable of producing large hail (generally 1-1.75 inch diameter) and isolated strong-severe gusts (50-60 mph). The environment farther south will favor a long-track supercell or two from eastern NE this evening into western/central IA through early tonight, potentially affecting Omaha and Des Moines. Steep midlevel lapse rates, MLCAPE of 2000-2500 J/kg and long hodographs through a deep layer will favor swaths of very large hail (up to 3 inch diameter or greater) and occasional severe gusts of 60-70 mph. There will be a narrow window of opportunity for a couple of tornadoes this evening with sufficient moisture (boundary-layer dewpoints near 60 F) as low-level shear increases. ...Thompson/Grams.. 04/17/2025 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .