Subj : DAY2SVR: Enhanced Risk To : All From : Mike Powell Date : Fri Jun 30 2023 15:08:00 ACUS02 KWNS 301730 SWODY2 SPC AC 301728 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Jun 30 2023 Valid 011200Z - 021200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF EASTERN MISSOURI...CENTRAL AND SOUTHERN ILLINOIS...WESTERN INDIANA AND WESTERN KENTUCKY... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MID-MISSISSIPPI VALLEY TOWARD THE CENTRAL APPALACHIANS...AND PARTS OF FAR SOUTHEAST NEW MEXICO INTO SOUTHWEST TEXAS... ....SUMMARY... Severe thunderstorms will be possible tomorrow/Saturday, from the central and southern Appalachians region westward through the Ohio/Tennessee Valleys into the mid-Mississippi Valley. Severe winds are the greatest concern, especially from eastern Missouri into western Indiana. ....Synopsis... A mid-level trough will traverse the central MS Valley region as a second upper trough grazes the northwestern CONUS tomorrow (Saturday). Ahead of the MS Valley mid-level trough, abundant low-level moisture will be in place from the MS River to the Atlantic Coast, fostering scattered to widespread thunderstorm potential. Storms from today (Day 1) should be ongoing at the start of Day 2 (Saturday) from the Plains into the OH Valley. Deep-layer ascent associated with the progressing mid-level trough over the Midwest, as well as low-level convergence along a trailing cold front across the Southern Plains, will foster an increase in convective coverage and intensity through the day, with severe storms possible, especially across the Mid-MS Valley. ....Mid-MS Valley to the central Appalachians... A complex severe weather scenario is expected to unfold across the Midwest into the OH/TN Valley areas tomorrow, with later day activity predicated on earlier day storms. At least scattered thunderstorms (perhaps in the form of organized multicells/MCSs) should be ongoing at the start of the period from the Midwest and points east. Despite the variability in potential placement and timing of earlier convection and subsequent impact on boundary-layer modification, the latest guidance has come to a consensus that an organized round of severe storms should occur from the mid-MS valley and points east during the afternoon hours. Along the periphery of the upper ridge, the embedded mid-level trough should support convective initiation to the west of the MS river by afternoon, where 70+ F surface dewpoints are overspread by 8 C/km mid-level lapse rates, resulting in 2000-3000 J/kg MUCAPE. Strong speed shear with height will support elongated hodographs and in turn, thunderstorm organization. Much of the latest convection-allowing guidance portrays MCS development, with the potential for severe winds, occasional bouts of large hail, and perhaps a tornado or two. The MCS should form in MO by early afternoon and progress eastward toward the Appalachians by early evening, where Category 2/Slight Risk probabilities are in place. A Category 3/Enhanced Risk also exists from the eastern MO into western IN/KY, where confidence is highest in a relatively greater concentration of severe gusts occurring during the mature stage of the forecast MCS. ....Portions of the Hudson Valley... Ahead of a surface lee trough, diurnal heating of a moist low-level airmass will promote enough boundary layer destabilization to support convective initiation across the Hudson Valley into the central Appalachians during the late morning/early afternoon hours. Given relatively poor mid-level lapse rates, tall and thin CAPE profiles will promote enough buoyancy for strong but brief pulse cellular convection and perhaps multicells when factoring in mediocre vertical shear profiles. The strongest storms may produce isolated severe wind/hail during the afternoon/evening hours, warranting the maintenance of Category 1/Marginal Risk probabilities this outlook. ....Southern Plains into the southern High Plains... Thunderstorms may be ongoing at the start of the period across the Southern Plains near the southward-sagging cold front. Through the day, surface heating will destabilize the boundary layer as 7-8 C/km mid-level lapse rates overspread mid to upper 60s F surface dewpoints. 1000-2000 J/kg SBCAPE should manifest across the southern Plains, with over 3000 J/kg SBCAPE possible closer to the Trans Pecos in southwest TX. Vertical shear magnitudes should be modest at best (generally under 30 kts of effective bulk shear). However, elongated hodographs suggest that relatively robust multicellular convection may initiate by afternoon, both along the cold front in central OK into western TX, and along a dryline in western TX. Severe wind/hail may accompany the more intense multicell clusters that form, with the best chance for severe occurring across far southeast NM into southwest TX, where a Category 2/Slight Risk has been introduced. ...Squitieri.. 06/30/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .