Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 27 2023 07:31:57 ACUS03 KWNS 270731 SWODY3 SPC AC 270731 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 AM CDT Tue Jun 27 2023 Valid 291200Z - 301200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GREAT LAKES AND LOWER OHIO VALLEY... ....SUMMARY... A severe threat, with a potential for wind damage and large hail, appears likely to develop on Thursday across parts of the southern Great Lakes region into the lower Ohio Valley. An isolated severe threat may also develop in parts of the central High Plains. ....Great Lakes/Lower Ohio Valley... A mid-level anticyclone will be in place across the southern U.S. on Thursday. North of the anticyclone, a subtle shortwave trough, and an associated 40 to 55 knot mid-level jet, will move eastward towards the southern Great Lakes. At the surface, a cold front will advance southeastward across the Upper Midwest. Ahead of the front, surface dewpoints will be in the upper 60s and lower 70s F across much of the mid Mississippi Valley. By afternoon, an axis of strong instability is forecast to develop from northern Missouri eastward into central Illinois, with an instability axis extending southeastward into the Tennessee Valley. Thunderstorms appear likely to develop on the northwestern edge of the moist airmass along and near the front in the afternoon. The storms are forecast to move southeastward into the stronger instability. An MCS will be possible by early evening. NAM forecast soundings around 21Z in the Chicago Metro, near the instability axis, have MLCAPE peaking around 4000 J/kg, with 0-6 km shear near 45 knots. This, combined with steep lapse rates around 8.0 C/km will be favorable for supercells with large hail. A wind damage threat will also be possible, especially if a cold pool can organize. An isolated tornado threat could also develop. The main uncertainty is concerning convective coverage. At this time, the models are mostly in agreement that a cluster will initiate in southern Wisconsin and move southeastward into the stronger instability across northern Illinois. Further to the northeast, more uncertainty exists for not only convective initiation but instability as well. There is considerable spread in the models for these two factors over lower Michigan. Still, an isolated severe threat could develop in lower Michigan if enough instability materializes. ....Central High Plains... An upper-level trough will develop across the Intermountain West on Thursday, as mid-level flow remains from the southwest across the central High Plains. At the surface, upslope flow is forecast across the central High Plains, and this will ensure that moisture is pushed westward toward the higher terrain of north-central Colorado. As surface heating takes place, thunderstorms may form in the higher terrain of north-central Colorado or further northeast in western Nebraska. Moderate instability and strong deep-layer shear is evident on forecast soundings in these two areas, suggesting a severe threat will be possible in each. The main uncertainty is which of the two areas will be favored for convective initiation. Concerning convective potential, the NAM has greater potential further west with the ECMWF further northeast. If the model solutions can become in better agreement concerning this, then a slight risk may need to be added in the next outlook update. ...Broyles.. 06/27/2023 $$ = = = 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) .