SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1139 AM CDT Sat Sep 23 2023 Valid 231630Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN KANSAS...WESTERN MISSOURI...EASTERN OKLAHOMA AND FAR NORTHWEST ARKANSAS... ...SUMMARY... Large to very large hail, wind damage and a few tornadoes will be possible today across parts of the Upper Midwest, Lower Missouri Valley to the southern Plains. A tornado or two may also occur in parts of the coastal Mid-Atlantic. ...Upper Midwest/Lower Missouri Valley/Southern Plains... A cluster of storms with history of periodic large hail/severe-caliber wind gusts this morning across eastern Nebraska persists into western Iowa at midday, while generally trending downscale and a bit weaker. These storms seem likely to outpace the primary reservoir of buoyancy with greater early-day inhibition with eastward extent, but some short-term severe risk may nonetheless continue. This convection casts some uncertainty regarding the northward extent of more appreciable surface-based destabilization later today, but strong/potentially severe thunderstorm redevelopment is still expected later this afternoon near the surface wind shift/occluded front. This would primarily be the case beginning around mid/late afternoon, coincident with the approach of the upper vort/speed max over South Dakota/northern Nebraska/northwest Iowa vicinity. At least a modest corridor of severe-conducive instability may materialize especially across northwest Missouri/west-central Iowa and southwest/south-central Minnesota. Supercell-favorable hodographs will reside across much of the region, with the potential for large hail, damaging winds, and possibly tornadoes, particularly if more cloud breaks/destabilization occurs in proximity to the surface low/triple point. Farther south, another corridor of persistent convection since mid-morning has been across far eastern Kansas into northwest/western Missouri. These storms have occasionally produced severe hail, and this may continue for a time this afternoon even as warm advection/850 mb convergence weakens. The primary scenario is otherwise expected to near-frontal deep convective development late this afternoon into evening, with a moderate to strongly unstable environment, particularly to the southwest of the eastern Kansas/northwest Missouri early day storms. Steep lapse rates/ample buoyancy and enlarged hodographs will support initial supercell potential, capable of very large/damaging hail, severe wind gusts and possibly some tornado risk, with storms tending to grow upscale during the evening. CAPE will lessen somewhat with southwestward extent into north-central/northwest Texas where greater boundary-layer mixing and lesser dewpoints will be found, but with greater DCAPE and downdraft-acceleration potential in support of local wind threat. ...Mid-Atlantic States/Tidewater... Currently centered over northeast North Carolina, Tropical Storm Ophelia is expected to continue to weaken as it generally moves north-northeastward through tonight. Reference the National Hurricane Center for latest details. Even while the system will gradually weaken, some tornado risk will focus along coastal areas of southeast Virginia toward the Delmarva today, and possibly eventually as far north as New Jersey. Any such potential is expected to generally relate to convection that can deepen/sustain and pivot toward the coast, especially if it interacts with the warm front where low-level/deep-layer shear will be maximized with surface-rooted buoyancy. ..Guyer/Dean.. 09/23/2023
