SPC AC 061731 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1231 PM CDT Sat May 06 2023 Valid 071200Z - 081200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN NEBRASKA...IOWA...NORTHERN MISSOURI...EXTREME WESTERN ILLINOIS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF NORTHWEST TEXAS INTO FAR SOUTHWESTERN OKLAHOMA... ...SUMMARY... Severe storms with very large hail, hurricane force gusts, and isolated tornadoes will be possible across parts of the Mid Missouri Valley on Sunday. Severe wind/hail producing storms will also be possible in parts of the central and southern Plains, perhaps extending into parts of the southern Great Lakes and Ohio Valley into the Tennessee Valley and central Appalachians. ...Synopsis... A relatively complex convective scenario is in store for tomorrow/Sunday. An upper ridge will become established over the Mid-MS Valley and OH Valley regions while a mid-level trough will meander over the Interior West. Multiple mid-level impulses are expected to crest the ridge through tomorrow, potentially supporting multiple rounds of storms (including possible MCSs), some of which may be capable of supporting severe hazards. Meanwhile, a surface low and trailing dryline will become established across the Central and Southern Plains. Despite relatively weak shear in the presence of capping, some storms may develop across the southern Plains, supporting a severe threat. ...Central Plains into the Midwest... Multiple intense thunderstorms are expected to develop along a warm frontal zone across eastern NE into IA by late afternoon. Upper 60s to low 70s F dewpoints beneath 8+ C/km mid-level lapse rates will support over 4000 J/kg SBCAPE in spots amid elongated, slightly curved low to mid-level hodographs. Initial development should be supercellular with very large hail possible and perhaps a couple of tornadoes possible. However, overall modest shear profiles support supercell mergers into an intense MCS somewhere from far eastern NE into the southern half of IA by evening. Should this occur, a bow-echo MCS may manifest and produce several instances of severe gusts, a few of which may exceed 65 kts. ...Southern Plains... Isolated to potentially scattered thunderstorms should rapidly develop ahead of the dryline by afternoon peak heating. Upper 60s/lower 70s F surface dewpoints beneath 8-9 C/km mid-level lapse rates will support up to 4000 J/kg MLCAPE wherever low-level moisture does not mix out. Some guidance suggests that the development of a well-mixed boundary layer may result in only 2500 J/kg MLCAPE. Nonetheless, very high amounts of buoyancy amid steep tropospheric lapse rates should support intense thunderstorm development. With somewhat elongated hodographs, initial updrafts may be transient supercellular, with the risk of large hail. However, weak low-level shear should support outflow dominant storms with a severe wind threat. ...Mid MS Valley, TN/OH Valleys, Central Appalachians... Multiple MCSs may occur through the day, with an MCS expected to be traversing the mid-MS Valley into the OH/TN Valley areas at the start of the period (Sunday morning). This MCS should be in the weakening stages due to the stabilizing of the boundary layer. However, the MCS will move southeast along the eastern periphery of the upper ridge and 7+ C/km mid-level lapse rate plume, where at least some deep-layer and low-level shear will be present. As such, a few damaging gusts may still occur, including over portions of the central Appalachians, where increased diurnal heating may support a brief re-invigoration of convection along the leading line. It is possible that the intense MCS moving across the Midwest during the evening may approach the Mid MS, OH and TN Valleys overnight. Should this MCS endure, isolated damaging gusts will again be a concern. ...Portions of the northern High Plains... Scattered thunderstorms may develop along the higher terrain of the Black Hills by afternoon peak heating in the presence of surface lee troughing. A warm, but dry boundary layer is expected to materialize by late afternoon in advance of the storms, with up to 9 C/km low-level lapse rates expected. Modest strengthening of the vertical wind profile will contribute to elongated hodographs, fostering the potential for storm organization. As such, short line segments may produce isolated severe gusts during the late afternoon hours. ..Squitieri.. 05/06/2023 CLICK TO GET WUUS02 PTSDY2 PRODUCT NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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