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SPC May 8, 2023 1730 UTC Day 2 Convective Outlook

2 years 2 months ago

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Mon May 08 2023 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SOUTHERN KANSAS INTO NORTHERN OKLAHOMA AND THE CAROLINAS... ...SUMMARY... Scattered strong to severe thunderstorms with an attendant severe hail/wind threat are expected across parts of the southern Plains and the Mid-Atlantic coast Tuesday afternoon. A more isolated severe threat will likely emerge across parts of the central and northern High Plains. ...Synopsis... The upper-level flow regime is expected to gradually amplify over the next 48 hours across the CONUS with ridging over the central Plains and the deepening of the upper low currently along the West Coast. At the surface, seasonal moisture will remain in place across the southern CONUS with modest moisture return into the central Plains amid weak cyclogenesis over the TX Panhandle. The potential for organized convection will likely be greatest over the southern Plains and High Plains, as well as across the Mid-Atlantic, where the overlap of strong buoyancy, adequate deep-layer shear, and forcing for ascent appears most probable. ...OK/KS... A weak cold front currently over the central Plains is forecast to retreat northward as a diffuse warm front as a weak surface low organizes over the TX/OK Panhandle region. Along and south of this boundary, rich low-level moisture in the form of mid to upper 60s dewpoints will be common and slowly spread west/northwest into parts of southwest KS. This may result in some sharpening of the dryline, and combined with mid-level lapse rates on the order of 8 C/km, will promote strong instability upwards of 3000-4000 J/kg MLCAPE across the warm sector. Despite the favorable instability, upper-level ridging will mute broad-scale ascent and limit deep-layer shear from southern KS southward. A zone of favorable overlap of strong buoyancy and adequate (around 30 knots of effective bulk shear) appears most likely from the dryline/warm front intersection near the surface low eastward along the frontal zone into southern KS/northern OK. While a tornado or two is possible given favorable low-level helicity along the frontal zone and in the vicinity of the surface low, uncertainty regarding storm coverage and mode suggests large hail and damaging winds will be the primary hazard, especially with initially discrete cells. Further south along the dryline, strong diurnal heating will quickly erode surface-based inhibition. Weak forcing for ascent casts considerable uncertainty onto storm coverage, and this is reflected in recent CAM guidance with little to no convective signal. However, a deep, well-mixed boundary layer over west TX suggest any convection that does develop may feature strong/severe downburst winds. This potential appears most probable across the Trans Pecos region of southwest TX where orographically-initiated convection may develop. ...Central/Northern High Plains... Isolated convection will likely develop within a weak upslope flow regime along the central to northern High Plains. Marginal moisture return should be adequate to allow discrete cells and/or clusters to propagate eastward into the late evening hours. Stronger deep-layer flow will likely support storm longevity and organization, but MLCAPE values will likely be limited to 500-1000 J/kg and may modulate storm intensity to some degree. Regardless, an severe hail/wind risk appears probable. ...Mid-Atlantic... A diffuse stationary frontal boundary draped across the OH River Valley will likely be convectively reinforced and shunted southward over the next 12-24 hours. This boundary should be zonally draped across the southern Appalachians into the Mid-Atlantic by Tuesday morning. Daytime heating, combined with low to mid-60s dewpoints, should allow low-level parcels to approach their convective temperatures in the low to mid-80s with minimal inhibition and around 1000 J/kg MLCAPE by early afternoon. Weak ascent associated with a mid-level perturbation should support isolated to scattered thunderstorm development. Effective shear vectors near 30 knots oriented along the frontal zone may foster upscale growth from initially discrete cells capable of marginally severe hail to clusters with an increasing damaging wind risk through late afternoon. ..Moore/Jewell.. 05/08/2023 Read more