Subj : ENHANCED RISK - So Plains To : All From : Dumas Walker Date : Wed May 15 2024 09:04 am ACUS01 KWNS 150600 SWODY1 SPC AC 150559 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Wed May 15 2024 Valid 151200Z - 161200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE SOUTHERN PLAINS... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL FLORIDA AND PARTS OF THE CAROLINA PIEDMONT... ....SUMMARY... Several severe thunderstorms should move across the southern Plains this afternoon and evening, accompanied by severe gusts (some possibly exceeding 75 mph), large hail, and perhaps a couple of tornadoes. Scattered severe thunderstorms are also possible this morning into the afternoon over parts of the northern and central Florida Peninsula, as well as the Carolinas. ....Synopsis... A mid-level trough will progress across the Southeast as a second mid-level trough impinges on the southern Plains today. Along the East Coast, a weak surface low will impinge on the Atlantic Coastline as a surface baroclinic boundary drapes across the central FL Peninsula. Moisture advection ahead of the surface low over the Carolinas, and south of the baroclinic boundary over the central FL Peninsula, will encourage strong to potentially severe thunderstorm development given the presence of adequate vertical wind shear. Meanwhile, strong moisture advection ahead of a rapidly developing surface cyclone over the southern High Plains will promote the development of several severe thunderstorms by afternoon peak heating over the southern Plains. ....Central FL Peninsula... Thunderstorms should be initiating and strengthening along a baroclinic boundary across northern into central portions of the FL Peninsula by the start of the period (12Z) today. During the morning, a 50+ kt westerly 500 mb jet streak will overspread the baroclinic boundary, where 30+ kts of southwesterly 850 mb flow will also be in place, contributing to curved, elongated hodographs. 30-40 kts of effective bulk shear, combined with 2000-3500 J/kg SBCAPE (driven by 7+ C/km mid-level lapse rates overspreading mid 70s F dewpoints) could result in semi-discrete supercell structures. However, a predominantly linear convective mode could be favored, as the mean wind field will largely parallel the surface baroclinic boundary. Severe wind and hail should be the main threats, though a couple of tornadoes could also occur, especially if any supercell structures can maintain themselves ahead of the convective line. ....Carolinas... Ahead of the weak surface low, adequate boundary layer heating and moistening should occur beneath 6.5-7 C/km low and mid-level lapse rates, supporting a marginally unstable but uncapped airmass by afternoon. The combination of surface heating and some dynamic lifting induced by the approaching mid-level trough, will support late morning/early afternoon thunderstorm initiation. Stronger westerly flow aloft from the mid-level trough will overspread the warm sector, contributing to 30-40 kts of effective bulk shear. Also, with the onset of diurnal heating, surface temperatures warming into the low 80s F amid mid 60s F dewpoints will boost SBCAPE to at least 1500 J/kg. Given relatively elongated, straight hodographs, splitting supercells and merging multicells should occur through the afternoon, accompanied by a severe wind and hail risk. ....Southern Plains... Surface lee troughing along the southern High Plains should become generally more pronounced with increasing deep-layer ascent, driven by an approaching mid-level trough. Through the afternoon, strong diurnal heating will contribute to the development of a deep, well-mixed, uncapped boundary layer. 8-9 C/km lapse rates will reside in the boundary layer and into the mid-levels, resulting in inverted-V profiles across the TX panhandle with 1500-3000 J/kg of tall, thin CAPE. Initial storms should be high-based, with supercells and multicells possible given modestly curved, elongated hodographs. Large hail and severe gusts will be the initial concerns. However, ample evaporative cooling within the deep, well-mixed boundary layer will encourage the development of deep, strong cold pools with a tendency to merge. Severe-wind-producing clusters are expected to rapidly propagate from the TX/OK Panhandles into northwestern OK and eventually southern KS by late afternoon/early evening, preceded by richer low-level moisture and a strengthening low-level jet. These conditions may augment severe wind production (including the potential for 65+ kt gusts) with the stronger storm clusters. Supercell structures may also initiate in the warm-air advection regime along the KS/OK border during the evening, with all severe hazards possible, before storms are overtaken by merging cold pools from the west. Storms should gradually weaken overnight as they either become undercut by overly aggressive cold pools, or they outpace the buoyancy axis by the time they reach far eastern KS/northeastern OK. More isolated thunderstorms may initiate along a diffuse dryline across western TX toward the Rio Grande. Given overall weak forcing, confidence in thunderstorm development and sustenance is not overly high. Nonetheless, over 1500 J/kg SBCAPE amid elongated hodographs suggests that any storm that can form and mature may become supercellular, accompanied by severe wind and hail. ...Squitieri.. 05/15/2024 $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175) .