Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 24 2023 12:57:56 ACUS01 KWNS 241257 SWODY1 SPC AC 241256 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0756 AM CDT Thu Aug 24 2023 Valid 241300Z - 251200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GREAT LAKES... ....SUMMARY... Scattered severe thunderstorms producing damaging winds, large hail, and perhaps some tornado risk are expected late this afternoon through tonight across parts of the southern Great Lakes region toward the central Appalachians. Some of the wind gusts could be significant (75+ mph). ....Great Lakes/Ohio Valley to Mid-Atlantic States... A considerable amount of generally decaying convection and outflow persists early this morning across much of Ohio/far southeast Lower Michigan and nearby parts of eastern Indiana and northern Kentucky. A few stronger updrafts will continue on the southern/southwest flanks of this activity in proximity to the regional reservoir of instability, potentially including some strong wind gusts for a time this morning. Consequential air mass impacts have occurred from this convection, but summertime insolation/heating and eastward advection of a very unstable air mass that resides over much of Indiana/southwest Lower Michigan (and points west) will lead to steady recovery this afternoon. Even with scattered/persistent convection, the 12z observed sounding from Detroit sampled ample buoyancy with 4000+ J/kg MUCAPE and steep mid-level lapse rates of 7+ C/km. Accordingly, strong to locally extreme instability (MLCAPE 3000-5000+ J/kg) is expected along/south of a weak front from southern Wisconsin/northern Illinois into Lower Michigan later today. This very favorable thermodynamic environment will be aided by the prevalence of 70s F surface dewpoints, steep mid-level lapse rates and robust daytime heating. After the early day convection gradually subsides, considerable mid-level warmth (700 mb temperatures 10-14C) will likely cap the warm sector through the diurnal heating cycle. A low-amplitude mid-level disturbance and related speed max over northeast Minnesota/Lake Superior and nearby Ontario this morning will continue east-southeastward, with implications that forcing for ascent and strengthening westerlies will at least somewhat overlie and influence the near-surface wave/frontal vicinity by evening, within a west-east corridor across southern Lake Michigan, southern/central Lower Michigan toward the Lake Erie vicinity. This same corridor is where deep convection is most likely to initiate by around sunset. Intense storm development can be expected including some initial supercells capable of large hail and possibly a tornado risk, which could somewhat focus across southeast Lower Michigan near the warm front/surface wave. Storms will likely quickly further increase and organize into mid/late evening (and beyond) toward the Lake Erie general vicinity including northern Ohio/western Pennsylvania, with damaging wind potential becoming more prevalent. Given the potential for extreme instability, some threat for isolated 75+ mph winds may exist as an MCS matures, with some possibility of a QLCS-related tornado risk also persisting. The severe wind threat should continue through the evening into and across parts of the upper Ohio Valley and central Appalachians before convection eventually weakens. Portions of the region will be reevaluated in subsequent outlooks for a somewhat higher/focused severe potential. ....Northern/Central Plains... Ascent associated with a shortwave trough along the international border, along with modest low-level convergence along a weak front, should encourage convection to develop late this afternoon across parts of North Dakota. Weak to moderate instability and strong deep-layer shear should support organized updrafts, with multicells and perhaps a supercell or two possible. Isolated hail and severe wind gusts should be the main threat with these thunderstorms as they move eastward into parts of northwest Minnesota through this evening. Confidence in greater coverage of severe convection across North Dakota still remains too low to include higher severe hail/wind probabilities at this time, but this will continue to be reevaluated in subsequent outlooks. Farther south/southwest, a somewhat separate area of convection should form this afternoon from the Black Hills vicinity of South Dakota into parts of western/northern Nebraska along/near a weak front. While deep-layer shear should be weaker with southward extent across this area, it may still be sufficient for loosely organized multicells, and perhaps a marginal supercell, posing an isolated hail/wind threat through the early evening. ...Guyer/Goss.. 08/24/2023 $$ = = = 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) .