Subj : DAY1SVR: Day 1 Convective To : All From : Mike Powell Date : Thu Aug 10 2023 08:13:00 ACUS01 KWNS 101244 SWODY1 SPC AC 101242 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 AM CDT Thu Aug 10 2023 Valid 101300Z - 111200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EASTERN NC/FAR SOUTHEAST VA AND PARTS OF THE UPPER MIDWEST INTO NORTHEAST NE... ....SUMMARY... Mainly isolated severe thunderstorms are expected over parts of the eastern and central states this afternoon into tonight. The most probable areas for potentially scattered coverage are across the eastern North Carolina/southeast Virginia vicinity and parts of the Upper Midwest into northeast Nebraska. ....Eastern NC/southeast VA vicinity... A broad swath of convection persists from southwest VA across northern parts of GA to MS. This convection was progged by some guidance to deteriorate east of the southern Appalachians but has failed to do so as renewed development has recently occurred over upstate SC within a low-level warm advection regime. A remnant MCV near the TN/NC/VA border area should track into coastal southeast VA by early to mid-afternoon. It seems increasingly likely that morning convection will spread east across eastern NC and southeast VA ahead of stronger boundary-layer destabilization and this should serve to marginalize the overall severe threat. There is still a conditional scenario where convective redevelopment occurs during the late afternoon ahead of a secondary shortwave impulse moving east from the TN Valley. With a 50-55 kt 500-mb jetlet centered across eastern NC during this time frame, deep-layer shear profiles would be conducive to a few supercells. If this occurs, overall spatial extent of this threat will likely be more limited than previously forecast. Conditionally, a tornado or two, and a swath of damaging winds along with isolated severe hail remain possible. ....Upper Midwest to eastern NE... As a mid/upper ridge shifts east, a low-amplitude trough will overspread the northern Great Plains. This will help induce a weak surface cyclone over western ND with a surface trough arcing south into central NE and a warm front extending southeast through southern MN. Relatively modest boundary-layer moisture and deep-layer shear will be limiting factors to a more prolific severe threat across the region. But steeper mid-level lapse rates within an elevated mixed layer will spread east across most of SD and much of NE by early evening and support a confined corridor of moderate buoyancy with MLCAPE of 1000-2000 J/kg. Effective bulk shear of 25-35 kts should support a mixed mode of a few supercells and multicell clusters. The most likely zone for scattered thunderstorm development in the late afternoon should be near the surface trough/warm front intersection in the northeast SD border area with ND/MN. Increasingly isolated development should trail south along the trough. A mix of large hail and severe wind gusts will be the main threats, likely becoming more marginal in terms of intensity/coverage with eastern extent into MN/IA, especially after sunset as convection becomes increasingly elevated. ....Mid-South/TN Valley... Convectively reinforced outflow from lingering thunderstorms this morning should serve as a focus for redevelopment later this afternoon. Another round of low-level warm theta-e advection driven storms should occur after sunset tonight. A modest combination of mid-level lapse rates and vertical shear should support a mainly isolated severe threat, with sporadic instances of damaging gusts and marginal hail. ....Coastal Mid-Atlantic to southern New England... Low-level warm theta-e advection will strengthen today and translate northeast from the Mid-Atlantic across New England this afternoon and evening. Low-topped convection should eventually develop amid meager surface-based instability as thermodynamic profiles become saturated. Potential for a brief tornado exists owing to enlarged low-level hodograph curvature, but this probability appears to be rather low. ....Central High Plains... Isolated high-based thunderstorms should develop off the higher terrain of southeast WY and far north-central CO near a lee surface trough. A deep mixed boundary layer along the adjacent High Plains could support a few severe wind gusts during the late afternoon to early evening. ....West-central/northwest TX... Hot surface temperatures along the dryline may support isolated late afternoon to early evening thunderstorm development. Should deep convection become sustained, the very deeply mixed boundary layer could yield a few severe wind gusts. ...Grams/Dean.. 08/10/2023 $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .