Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jun 17 2023 17:32:38 ACUS02 KWNS 171732 SWODY2 SPC AC 171731 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Sat Jun 17 2023 Valid 181200Z - 191200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY... ....SUMMARY... Severe thunderstorms are expected on Sunday from portions of the Ozarks to the central Gulf Coast states. Damaging gusts and large hail (some 2+ inches in diameter) will be the main hazard with these storms. A severe gust or two may also occur across eastern Montana. ....Synopsis... A mid-level shortwave trough will progress across the southern Plains into the Lower MS Valley as a second (longer-wave) upper trough deepens across the Interior West tomorrow/Sunday. Low-level warm-air advection will continue to transport ample low-level moisture to a northwest-southeast oriented baroclinic zone draped across the Lower MS Valley, which will be reinforced by ongoing convection at the start of the period. Overspreading this baroclinic zone and axis of low-level moisture advection will be an elevated mixed layer/steep mid-level lapse rates, which will promote strong buoyancy. The combination of persistent deep-layer ascent, buoyancy, and adequate vertical shear across the Lower MS Valley will support multiple rounds of strong to severe thunderstorms. Meanwhile, scant buoyancy preceding very strong ascent across portions of eastern Montana may promote strong storm development. ....Lower MS Valley... A complex scenario is expected for the Lower MS Valley region, as multiple rounds of strong to severe storms are expected, with each round likely influencing the intensity, placement, and timing of subsequent rounds of convection. One or more remnant MCSs from the Day 1 period are expected to be ongoing at the start of the day (12Z Sunday) across the Lower MS Valley, possibly accompanied by severe wind gusts. As this MCS(s) outpace the stronger buoyancy and dissipate near the Gulf Coast, surface heating should occur the Arklatex vicinity as 8+ C/km 700-500 mb lapse rates overspreads the region. By afternoon, these lapse rates overspreading greater than 80/70 F surface temperatures/dewpoints will yield well over 3000 J/kg MLCAPE. Strong mid-level flow overspreading the Lower MS Valley will also support elongated hodographs, with over 40 kts of effective bulk shear likely. As such, re-invigoration or redevelopment of convection should occur, with supercells producing large hail the initial mode. Given the steep lapse rates/strong buoyancy and length of the upper-level hodographs, 2+ inch diameter hail is possible. Storms are also likely to grow upscale into the evening hours, with severe gusts likely with any bowing segments that can materialize. Given the uncertainty in placement and timing of earlier rounds of storms, confidence is too low to point out potentially more focused corridors of widespread severe wind potential. ....Florida Peninsula... As remnant outflow boundaries/cold pools continue to surge southward across the Gulf from earlier (Day 1) storms, strong surface heating ahead of these outflow boundaries will serve as the impetus for renewed convective development. By late morning/early afternoon, strong storms should develop amid rich low-level moisture, but mediocre lapse rates (hence tall/thin SBCAPE profiles). Given weak to modest upper flow/shear, the stronger storms should be multicellular in nature, posing a threat for an instance or two of severe wind/hail. ....Central Texas... Limited lift ahead of a surface front will encourage isolated thunderstorm development across central TX by afternoon peak heating. However, surface dewpoints well over 70 F, overspread by 9 C/km mid-level lapse rates and strong mid-level flow, will encourage the development of isolated, splitting supercells. Severe wind and hail should accompany any storm that can mature and become sustained. Lower confidence in greater storm coverage/longevity precludes the addition of greater severe probabilities (including significant severe) at this time. ....Eastern Montana... Ahead of the approaching upper trough, steep low-level lapse rates will promote scant (but potentially adequate) buoyancy to support isolated thunderstorm development by afternoon. Efficient downward momentum transport of the stronger flow aloft may encourage a severe gust or two with any of the stronger storms that manage to develop. ...Squitieri.. 06/17/2023 $$ = = = 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) .