SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1135 AM CDT Wed Jun 13 2018 Valid 131630Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHERN APPALACHIANS AND PARTS OF THE CENTRAL GREAT PLAINS... ...SUMMARY... Scattered severe storms are possible, mainly during the late afternoon and evening across the northern Appalachians and parts of the central Great Plains. Large hail, damaging winds, and a tornado or two may occur. ...Northern Appalachians... A pronounced shortwave trough over the central Great Lakes will progress east towards ME through Thursday morning. An associated surface cyclone will track east across southern portions of Ontario and Quebec, with a cold front trailing southwest across the Lower Great Lakes, reaching the northern Appalachians this evening. Ongoing convection near the front across eastern Lower MI should intensify as it spreads into far southern Ontario before crossing over the international border and developing south across parts of NY/PA late this afternoon into the evening. Abundant stratus is prevalent from the Upper OH Valley eastward and this will temper diabatic heating over most of the region. However, the northeast periphery of mid-level lapse rates near 7 C/km (as sampled by 12Z APX/DTX soundings should overspread the warm sector, contributing to a modestly buoyant air mass with MLCAPE of 750-1500 J/kg. Deep-layer shear will become quite strong with increasingly elongated hodographs with approach of the shortwave trough, as a swath of 50+ kt 500-mb westerlies progresses east. Given substantial cross-boundary flow/shear vectors, a few supercells are anticipated within a broken band of storms along the front. Damaging winds, severe hail, and a tornado are possible, although the widespread clouds and late arrival of the cold front relative to peak heating should modulate a greater severe risk. ...Central Great Plains... A couple storm clusters are ongoing in associated with warm advection across northwest KS and near the SD/NE border. The southern convection may persist through the afternoon and develop eastward north of the stalled front in southern KS, where strong buoyancy along and south of the boundary will support a threat for isolated strong to severe gusts and marginally severe hail. The northern convection should persist through much of the afternoon amid continued robust warm advection, yielding a risk for a confined area of severe hail. Refer to MCD 721 for additional short-term information. Farther west, a few storms should form late afternoon into early evening near the dryline/front/outflow intersection in northeast CO and vicinity. Here, a veering wind profile with height along with very steep mid-level lapse rates near 9 C/km may support a conditional risk for a slow-moving supercell or two anchored near the boundary capable of large hail, severe wind gusts, and a tornado. ...Mid-MO Valley/IA... Warm advection will increase late tonight across the Mid-MO Valley into IA. Scattered to widespread elevated storm development is expected early Thursday. This area will be monitored for potential of marginally severe hail, but uncertainty is great enough to preclude adding any probabilities in this outlook. ..Grams/Nauslar.. 06/13/2018
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