Subj : DAY2SVR: Nws Storm Predic To : All From : Mike Powell Date : Fri May 05 2023 15:16:00 ACUS02 KWNS 051732 SWODY2 SPC AC 051730 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Fri May 05 2023 Valid 061200Z - 071200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE MID-MISSISSIPPI VALLEY AND FROM SOUTHERN OKLAHOMA INTO CENTRAL TEXAS... ....SUMMARY... Isolated severe thunderstorms producing hail and damaging gusts are possible across parts of the Mid-Mississippi Valley Saturday morning and afternoon. Additional severe thunderstorms capable of very large hail and damaging gusts are possible from southern Oklahoma into central Texas Saturday afternoon into early evening. A more limited risk for strong gusts and hail is possible across southern Mississippi and southeast Louisiana through Saturday afternoon. ....Synopsis... A low-amplitude mid/upper shortwave trough will shift northeast across the central Plains to the Upper Midwest on Saturday. This will bring a belt of enhanced southwesterly flow over the region. A more subtle shortwave impulse is forecast to migrates northeast across TX/OK during the afternoon/evening. Another impulse, likely associated with Day 1 convection over TX is forecast to spread east beneath an upper ridge over the Lower MS Valley. These features will focus thunderstorm potential on Saturday from the Upper Midwest through the MS Valley and across OK/TX. ....OK/TX... A surface dryline is forecast to extend south/southwest from southeast KS into central OK and west-central TX. Midlevel capping will likely suppress thunderstorm develop across northern OK into far eastern KS and western MO as this area will remain between the influence of wave ejecting further north toward the Upper Midwest, and the subtle wave migrating across TX. Strong heating along the dryline amid upper 60s to low 70s F surface dewpoints and very steep midlevel lapse rates will contribute to strong destabilization (3000+ J/kg MLCAPE) during the afternoon. Increasing midlevel moisture and subtle forcing from the midlevel shortwave impulse and from the dryline circulation should be sufficient to erode capping by peak heating. Isolated to scatter thunderstorms are expected by late afternoon. Deep-layer flow will remain somewhat modest, but vertically veering profiles will result in around 40 kt effective shear magnitudes, supporting initial supercells. Elongated hodographs above 2-3 km and lapse rates around 8-9 C/km suggest large to very large hail (greater than 2 inches) will be possible. Steep low-level lapse rates may also support strong outflow winds. The eastward extent of the threat will be limited by strengthening inhibition after loss of daytime heating given a lack of stronger ascent and warmer temperatures aloft. ....Mid-MS Valley vicinity... Large-scale ascent will be focused across eastern NE/SD into MN/WI by afternoon/evening as the shortwave trough migrates northeast. This influence of this shortwave will be limited with southward extent across the Mid-MS Valley. Capping will likely suppress thunderstorm activity west of the MS River. Nevertheless, southerly low-level flow will transport rich Gulf moisture northward into southeast IA and much of IL. Some elevated morning convection posing a risk for marginally severe hail is possible in this warm advection regime in the vicinity of east-central MO/west-central IL. This activity could persist along the moisture/instability gradient into western KY during the afternoon. Some wind/hail risk could accompany this activity though uncertainty in this scenario remains high. Additional thunderstorm development during the afternoon from southeast IA southward along the MS River appears more conditional given strong capping and nebulous large-scale ascent. If isolated convection develops and can become sustained, large hail and damaging gusts will be possible. ....Upper Midwest vicinity... Further north into eastern SD and the Upper Midwest, convection is likely to develop near a surface low over central/eastern SD and eastward along the warm front extending across southern MN into southwest WI. Cooler temperatures and more modest boundary-layer moisture this far north will limit instability. However, steep midlevel lapse rates greater than 7.5 C/km will aid in weak destabilization by late afternoon into the evening. Clusters of storms, potentially elevated with storm motion to the cool side of the warm front, may pose a risk for marginally severe hail and gusty winds. ....Lower MS Valley... Residual outflow from Day 1 convection and at least modest ascent associated with and eastward progressing impulse will provide support for thunderstorms on Saturday. Surface dewpoints in the low 70s F and warming into the 80s beneath steep midlevel lapse rates will support moderate instability. Capping above 850 mb will result in a somewhat uncertain/conditional risk, but most forecast guidance suggests at least a few storm will develop during the afternoon. Modest shear and rather weak deep-layer flow will likely limit longevity of intense/well-organized convection. Nevertheless, some risk of strong gusts and marginal hail could accompany this activity. ...Leitman.. 05/05/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .