Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 25 2023 20:02:35 ACUS01 KWNS 252002 SWODY1 SPC AC 252000 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Fri Aug 25 2023 Valid 252000Z - 261200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL ILLINOIS INTO PARTS OF INDIANA... ....SUMMARY... Isolated to scattered thunderstorms associated with strong wind gusts and marginally severe hail are possible this afternoon and evening from Kansas to Virginia and across Upper Michigan, with the somewhat greater threat focused from central Illinois into southwest Indiana. Only minor changes were made at 20Z, including adjusting low probabilities farther across eastern Upper MI ahead of a frontal wave, and expanding a low wind threat into more of southeast KS and southern MO where a few storms have formed within the hot air mass. A small 2% tornado area has also been added for the area from far southern OH into a small part of northeast KY. Here, objective analysis indicates 0-1 SRH near 100 m2/s2, which may aid rotation potential in the area north of the primary KY MCS. ...Jewell.. 08/25/2023 ..PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 25 2023/ ....IL/IN this afternoon/evening... An outflow-reinforced front extends from WV/southern OH to central IL, while a second outflow surge is moving southeastward into northern MO and west central IL. The merger zone of these two boundaries appears to be the more probable area for thunderstorm development this afternoon into IL, along the north gradient of the 78-80 F boundary-layer dewpoints. Modified 12z soundings and short-term model forecasts suggest that MLCAPE could exceed 4000 J/kg with weakening convective inhibition, while steep midlevel lapse rates will also result in large DCAPE (> 1200 J/kg). With most of the vertical shear (25-30 kt magnitudes) concentrated in the lowest 3 km, the primary convective mode is expected to be multicell clusters and perhaps a relatively short-lived supercell or two capable of producing damaging outflow winds. ....Eastern KY to VA through this evening... The remnants of overnight convection persist from WV into eastern KY. The warmest surface temperatures and higher dewpoints to the west across KY suggest that the preferred development of new storms will also be toward the west and southwest this afternoon, where isolated strong downburst winds will be possible. Farther east into VA, somewhat lesser boundary-layer moisture (mixed mainly into the mid-upper 60s) and lesser midlevel lapse rates will support weaker buoyancy (MLCAPE in the 1500-2000 J/kg range) compared to KY/southern OH. Despite the early passage of the convectively-enhanced midlevel trough, 25-30 kt midlevel flow will linger over VA/MD this afternoon. Thunderstorm development will be possible this afternoon along a weak lee trough, as well as any persistent differential heating zones (mainly across southwest VA) and along a cold front moving southeastward from PA. The overall threat for damaging winds with downbursts still appears to be best categorized as MRGL, so will maintain the 5% wind probabilities. ....Northeast MN into Upper MI this afternoon/evening... A pronounced midlevel shortwave trough is moving east-southeastward over the MN Arrowhead/Lake Superior. A narrow zone of destabilization coincident with a band of ascent will support at least widely thunderstorms through the afternoon. Though buoyancy will be modest (MLCAPE of 500-1000 J/kg), long hodographs will support organized/supercell storms capable of producing isolated wind damage and marginally severe hail. ....Eastern CO to KS/NE border this afternoon/evening... As the surface warms with daytime heating, high-based thunderstorm development is expected along a slow-moving front in KS and in a zone of low-level upslope flow in CO by mid-late afternoon. Vertical shear will be relatively weak, but deep inverted-V profiles with large DCAPE will support the potential for strong to isolated severe outflow gusts this afternoon into this 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .