Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Apr 03 2023 20:03:27 ACUS03 KWNS 032003 SWODY3 SPC AC 032002 Day 3 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0302 PM CDT Mon Apr 03 2023 Valid 051200Z - 061200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY FROM THE GREAT LAKES REGION AND OHIO VALLEY SOUTHWESTWARD INTO THE LOWER MISSISSIPPI VALLEY... AMENDED FOR SLOWING UPPER TROUGH, WESTWARD EXPANSION OF SEVERE THREAT ....SUMMARY... Severe thunderstorms are possible over a large area from the Great Lakes region southwestward to the Lower Mississippi Valley Wednesday. This may include cells capable of producing tornadoes and extensive wind damage, primarily north of the Ohio River, with other severe storms expected into the lower Mississippi Valley. This amendment is primary due to the slowing upper trough, and the westward expansion of severe probabilities. Severe storms may be ongoing as far west as the St. Louis area at 12Z Wednesday, with favorable conditions remaining for tornadoes and damaging winds expending mainly northeastward. Farther south, lower 70s F dewpoints and heating ahead of a cold front is expected to support scattered storms during the day into the lower MS Valley, where mainly hail and damaging gusts will be possible. This westward demarcation of the severe threat will likely be adjusted further incoming updates. ....PREVIOUS DISCUSSION... ....Synopsis... Within the more amplified branch of split flow emanating from the mid-latitude Pacific, the center of a broad and deep, occluding cyclone is forecast to migrate across and northeast of the Lake Superior vicinity before beginning to weaken Wednesday through Wednesday night. As this occurs, it appears that mid-level ridging centered along an axis across the Yucatan Peninsula into western Atlantic will remain a prominent influence across much of the Southeast, while short wave ridging also overspreads the Northeast and Canadian Maritimes. Models indicate that a narrow corridor of increasing low-level moisture, ahead of the cold front trailing the cyclone, will overspread much of the Ohio Valley and lower Great Lakes region. The trailing flank of the cold front probably will stall across the lower Mississippi Valley into northwestern Gulf coastal plain, beneath the northwestern periphery of the mid-level ridging. ....Lower Great Lakes into lower Mississippi Valley vicinity... Most model output generally indicates that the core of stronger southerly low-level flow, initially including 50+ kt around 850 from the Mid South through lower Michigan, will rapidly shift across the lower Great Lakes region and weaken some by mid afternoon, However, southwesterly mean flow on the order of 40-70 kt may linger as far southwest as the lower Ohio Valley through much of the day. This will contribute to an environment at least conditionally support of organized severe thunderstorm development. With sufficient destabilization, this may include an evolving squall line with embedded and perhaps preceding discrete supercells. Destabilization remains a bit uncertain, based on the latest model output, with perhaps considerable warm sector cloud cover inhibiting insolation. Based on ensemble output, the 03/00Z NAM might be a bit of an outlier indicating sizable mixed-layer CAPE developing across southern lower Michigan and adjacent portions of Indiana/Ohio by early Wednesday afternoon, perhaps beneath a remnant plume of modestly steep mid-level lapse rates. If it becomes more apparent in subsequent model output that this environment will materialize, severe probabilities will probably need to be increased, with the risk including at least a bit more appreciable potential for a couple of strong tornadoes. South of the Ohio Valley, through lower Mississippi Valley, severe weather potential appears more limited as low-level flow weakens along the stalling frontal zone. ...Jewell.. 04/03/2023 $$ = = = 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) .