Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Feb 27 2024 05:58:05 ACUS01 KWNS 270557 SWODY1 SPC AC 270556 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1156 PM CST Mon Feb 26 2024 Valid 271200Z - 281200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID MS AND LOWER OH VALLEYS INTO THE SOUTHERN GREAT LAKES.... ....SUMMARY... Scattered strong to severe thunderstorms, associated with large hail (some 2 inches diameter), damaging gusts, and a few tornadoes will be possible from late this afternoon into the evening and overnight, from parts of the mid Mississippi Valley to the Ohio Valley and southern Great Lakes. ....Synopsis... Low-amplitude, split mid-level flow over much of the central and western CONUS will gradually consolidate and amplify through the forecast period, as a northern-stream shortwave trough merges with strong southwesterly flow from the southern stream. Multiple weak perturbations embedded within the increasingly strong southern-stream flow ahead of the main vort max will aid in deepening a broad surface cyclone along a cold front over the northern Plains. As the surface low and trailing front advance, warm advection will draw limited, but sufficient, moisture northward into the lower OH Valley and Great Lakes. Strong to severe thunderstorms are possible ahead of the low and along the trailing front through early Wednesday. ....Mid MS and Lower OH Valley... Early in the forecast period, isolated to widely scattered thunderstorms may be ongoing within a strong low-level warm advection regime over the lower OH Valley. Ahead of the main surge of deeper surface moisture, these storms are expected to remain primarily elevated through the mid morning. Elevated buoyancy, steep lapse rates and sufficient vertical shear for supercells may support a conditional risk for large hail through mid morning. Continued warm advection should gradually transport upper 50s to low 60s F surface dewpoints northward into parts of southern and central IL, IN and western OH by mid afternoon. A diffuse moisture gradient along a surface pressure trough/weak dryline should become established across western/central IL into far eastern MO by late afternoon. Strong surface heating and confluence along this feature may support isolated convective development by 21-00z across central/northern IL. At the same time, warm advection along an expected differential-heating zone near the nose of the returning surface moisture may allow for scattered thunderstorm development across portions of northern IN, southern lower MI and northwestern OH. Model soundings show moderate MLCAPE (1500-2000 J/kg) and strong effective shear of 40-50 kt favorable for supercells. A prominent EML for February, with lapse rates of 8 C/km, will favor strong updrafts with efficient hail growth and a risk for significant hail. Later in the evening, the approach of the deepening mid-level trough and surface pressure falls ahead of the surface low across northern IL will yield increasing mass response across the warm sector. Model soundings show enlarged low-level hodographs potentially supporting a few tornadoes and damaging gusts. As the cold front and low move eastward, additional storm development is possible along the surface pressure trough and the surging cold front across portions of far eastern MO and southern IL. Uncertainty on storm mode and coverage remains fairly high, with some CAM solutions suggesting more isolated development ahead of the line, while other show mostly linear growth along the front. Regardless, these storms should continue eastward overnight across southern IN, northern KY and into southwestern OH with the potential for hail and damaging gusts. Should more discrete development occur and be maintained ahead of the building squall line, increasingly strong low-level shear (0-1km SRH of 250-400 m2/s2) could support a risk for tornadoes. The severe threat should gradually diminish into Wednesday morning as the frontal squall line pushes eastward into parts of eastern OH and the central Appalachians with decreasing buoyancy. ...Lyons/Darrow.. 02/27/2024 $$ = = = 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) .