Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 23 2025 19:46:00 ACUS01 KWNS 231944 SWODY1 SPC AC 231943 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Wed Jul 23 2025 Valid 232000Z - 241200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN HIGH PLAINS AND NEBRASKA INTO THE UPPER GREAT LAKES... ....SUMMARY... Scattered severe thunderstorms capable of producing damaging winds and potentially a tornado risk are possible across the Upper Midwest, mainly this afternoon and evening. Large hail may occur with supercells late today across parts of the northern High Plains. ....20z Update... The primary forecast amendment for this update is a reduction in severe probabilities across portions of northern MN and WI where the primary front and convective clusters/bands have passed and conditions are slowly stabilizing within the post-frontal regime. Across WI, 5% tornado probabilities have been adjusted southward to better align with recent convective trends and where short-range guidance shows the best overlap of low-level theta-e advection and wind shear later this evening. Although convective mode will be the primary modulating factor in the overall tornado threat, STP values should increase to between 1-2 later this evening as the nocturnal jet strengthens and should support at least some tornado potential. Elsewhere, the forecast remains on track per the previous discussion below. GOES IR imagery and echo top data shows an uptick in convective intensity across southeast MN and northern WI, and early stages of convective initiation are noted along the front southwestward into NE. These trends suggest a severe threat remains across the Plains/upper MS Valley regions. See MCDs #1761 and #1762 for additional details regarding the severe threat across portions of the northern High Plains and central NE. ...Moore.. 07/23/2025 ..PREV DISCUSSION... /ISSUED 1123 AM CDT Wed Jul 23 2025/ ....Mid Missouri Valley into the Upper Midwest/Great Lakes... Visible satellite/radar composite shows scattered thunderstorms late this morning from eastern SD into western WI, generally near and east of a surface low analyzed near the SD/MN border. A cold front extending from northern MN southwestward into the central High Plains will continue east-southeastward and provide a focus for additional storm development this afternoon/evening. Due in part to appreciable convection this morning and its related airmass influence across the Upper Midwest, uncertainty remains regarding the evolution of midday thunderstorm clusters and their associated severe risk this afternoon as the airmass immediately east/southeast of this activity continues to destabilize. A plume of richer low-level moisture (surface dewpoints in the mid 70s F) extends northward from the mid MS Valley into the upper MS Valley. Model guidance maintains a belt of moderate southwesterly 800-650 mb flow (30-35 kt) across the MN/IA/WI vicinity with slightly weaker flow indicated in the upper troposphere. The resultant hodograph structure should promote more linear configurations of storms. Models show the development of a more southwest-northeast oriented convective band later this afternoon across this region, which may subdue otherwise greater potential for severe gusts (being not oriented orthogonal to the mean wind in 800-650 mb layer), given the development of a very unstable boundary layer in areas void of convective overturning. Scattered severe/damaging winds appear to be the primary severe hazard but a tornado or two is possible, especially across MN into the WI vicinity. Storms are likely to develop farther southwest along the front in NE but weaker shear with south extent will limit the overall convective organization. However, severe gusts will probably occur with the more intense cores and surges with a linear band of storms through the evening before this activity gradually weakens. ....Northern/Central High Plains... No change was made to this portion of the outlook. A moist/post-frontal environment will favor scattered storm development later this afternoon. Relatively long/straight hodographs at mid/upper levels from the Black Hills into northeast WY will promote supercell development with the stronger updrafts. Large hail and severe gusts will be the primary hazards. Farther south, weaker flow will result in less organized storm modes, but isolated severe gusts/hail may occur with the stronger storms through early-mid evening. $$ = = = 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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .