Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 26 2024 19:59:36 ACUS01 KWNS 261959 SWODY1 SPC AC 261958 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Mon Aug 26 2024 Valid 262000Z - 271200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTH-CENTRAL PLAINS AND UPPER MIDWEST... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN NEW ENGLAND... ....SUMMARY... Severe thunderstorm wind gusts, large to very large hail and a couple of tornadoes are possible this afternoon through tonight especially across parts of South Dakota, northern Nebraska, central/southern Minnesota, and into Wisconsin. ....20z Update... The primary change with this outlook update was to expand the Marginal Risk southward across Virginia to account for ongoing convection that will track southward with potential risk for damaging wind. Instability will gradually weaken, however modest shear for organization may sustain this threat further south than previously forecast. The previous forecast remains on track with no changes needed based on recent observations and trends in guidance for the Enhanced Risk across the north-central Plains to Upper Midwest. A few initial supercells have developed across Minnesota. See MCD#2000 for more information. Further west across WY/SD, severe threat along the primary cold front continues with potential for enhancement of the earlier MCS moving eastward out of Wyoming. See MCD#1999 for more details on evolution of this severe threat. ...Thornton/Guyer.. 08/26/2024 ..PREV DISCUSSION... /ISSUED 1141 AM CDT Mon Aug 26 2024/ ....North-central Plains to Upper Midwest... A relatively active severe-weather day is expected regionally, especially late this afternoon through tonight, with multiple rounds of severe storms possible potentially including eastern South Dakota and parts of central/southern Minnesota into far western Wisconsin. Strong to locally severe storms have already occurred this morning across interior Wyoming, in relatively close proximity to the northeastward-ejecting shortwave trough that will cross the northern High Plains toward the Dakotas through tonight. This convection is thought to be harbinger of a broader/increasing severe risk that should develop this afternoon from far northeast/east-central Wyoming into southwest South Dakota including the Black Hills/Pine Ridge vicinities. Some initial supercells capable of large hail will be possible, but these storms should organize into an MCS and expand/intensify as activity proceeds into greater moisture, instability and post-frontal low-level flow to the east. These storms could persist eastward this evening across southern South Dakota/far northern Nebraska, and all the way into southern Minnesota/far northern Iowa overnight through the predawn hours. Another area of potential severe thunderstorm development including supercells will be across eastern South Dakota east-northeastward into central Minnesota early as mid/late afternoon near the front, where a very moist (middle to upper 70s F surface dewpoints) and very unstable (4000+ J/kg MLCAPE) air mass will reside. This could somewhat relate to ongoing thunderstorms across central South Dakota at late morning, or perhaps more likely, ahead of it into central Minnesota. While potentially intense severe storms/supercells are plausible, some uncertainty exists regarding the diurnal extent of deep convective development given the likelihood of residual mid-level capping. Even if diurnally related development through peak heating is more limited, severe-weather potential should steadily increase from west-to-east across east/southeast South Dakota, southern Minnesota/northern Iowa into western Wisconsin tonight via likely upstream MCS development. ....Northeast States/Mid-Atlantic... A belt of generally strengthening northerly flow aloft, along with modestly cool mid-level temperatures, will reside across the region on the western periphery on offshore-shifting upper-level trough. Coincident with low/some middle 60s F surface dewpoints, moderate destabilization (1000-1500 J/kg MLCAPE) is expected this afternoon across southern New England/eastern New York southwestward toward the Delmarva/coastal Mid-Atlantic. Multiple corridors of at least widely scattered south/southeastward-moving storms should evolve this afternoon, including southern New England/southeast New York as well as the Pennsylvania/Maryland/Virginia border vicinity. Isolated severe wind and hail will be possible this afternoon through early/mid-evening. For additional short-term information, see Mesoscale Discussion 1995. $$ = = = 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) .