Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 17 2025 16:31:34 ACUS01 KWNS 171631 SWODY1 SPC AC 171629 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1129 AM CDT Thu Apr 17 2025 Valid 171630Z - 181200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN NEBRASKA INTO 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... A belt of strong southwesterly mid-upper flow will extend from the southern High Plains to the central Great Plains and upper MS Valley, downstream of a large-scale trough over the West. Visible-satellite imagery late this morning shows a capped stratocumulus shield from eastern OK northward into eastern KS and the MO Valley. This low-level moisture depicted on satellite corresponds with a 10.0-11.5 g/kg lowest 100-mb mean mixing ratio and dewpoints in the upper 50s to lower 60s. Moisture will continue northward on southerly flow to the east of a weak surface wave which 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. Strong heating and continued moisture advection will result in moderate to strong destabilization from eastern KS to eastern NE/western IA and southern MN. Models continue to show initial thunderstorm development around 20z in southern MN and around 22z in eastern NE (near and just east of the cold front/dryline triple point). Model forecast soundings over 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), and perhaps a brief tornado. Farther south, greater buoyancy and elongated hodographs will be more favorable for supercells. A long-track supercell or two is forecast from eastern NE this evening into western/central IA through early tonight. Large to giant hail (peak diameter 2.75 to 3.5 inches) will be possible with the more intense phase of the supercell activity. A narrow window of opportunity may exist for a couple of tornadoes this evening with sufficient moisture (boundary-layer dewpoints near 60 F) as low-level shear increases. Severe gusts will be possible with the stronger storms before this activity wanes late this evening into the overnight. ...Smith/Jirak.. 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) .