SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Tue Jun 20 2023 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS... ...SUMMARY... Isolated to scattered severe thunderstorms are possible on Wednesday across portions of the Plains. Large hail and severe gusts will be the main hazards with this activity. Isolated strong storms also will be possible across parts of the Southeast, with an accompanying risk for damaging gusts. ...Northern to Southern Plains... An upper ridge will be centered from southwest TX to the upper Great Lakes on Wednesday. A large-scale upper trough will remain over the West, with a belt of strong southwesterly flow oriented over the Great Basin to the northern High Plains, somewhat displaced to the west of a corridor of strong instability over portions of the Plains. Forecast guidance depicts several subtle shortwave impulses migrating east from the Rockies into OK/TX, and from northeast CO/southeast WY into the Dakotas. This should provide sufficient support for clusters of severe thunderstorms from the Dakotas southward into OK/TX. At the surface, southerly low-level flow beneath the upper ridge will allow for a band of rich boundary-layer moisture spreading northward across the Plains. Surface dewpoints in the upper 60s to low 70s may extend as far north as eastern CO into southwest NE. Mid 60s F dewpoints are expected northward across eastern WY into central/eastern portions of the Dakotas. Steep midlevel lapse rates atop this moist boundary layer will foster MLCAPE values greater than 3500 J/kg (somewhat lower across the Dakotas). Thunderstorms are expected to develop along a stalled front across the Dakotas, and southward along/east of a dryline oriented across the central/southern High Plains. While deep-layer flow will remain somewhat light, vertically veering wind profiles will support 30-40 kt effective shear magnitudes. Elongated hodographs with small low-level curvature suggest initial supercells capable of large hail will be possible. Large instability and very steep low-level lapse rates also will support severe gusts. With time, some potential will exist for a couple of forward- propagating clusters to develop via mergers and consolidating outflows. Forecast guidance also suggests a modest low-level jet will increase during the evening, further supporting one or more bowing clusters. If this evolution occurs, severe/damaging-wind potential would increase during the evening. The most likely location for this to occur is expected to be across OK/TX and further north from northeast CO/southeast WY into western NE where forecast guidance is rather consistent in ejecting weak shortwave impulses during the late afternoon/evening. While there is some uncertainty with southward extent regarding evolution of severe potential, enough consistency exists among all forecast guidance to warrant a Slight risk (level 2 of 5) from the central High Plains into parts of OK/TX. ...Southeast... The persistent upper low over the Southeast will not move much on Wednesday. Vertical shear will be weaker than the past several days, but a seasonally moist airmass will remain in place. Scattered thunderstorms are expected across the Marginal risk (level 1 of 5) area through the day. Moderate to strong instability and high PW values will generally support isolated strong/locally damaging gusts. ..Leitman.. 06/20/2023
