SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1137 PM CST Wed Dec 23 2020 Valid 241200Z - 251200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST SOUTH CAROLINA...EASTERN NORTH CAROLINA TO SOUTHEAST VIRGINIA... ...SUMMARY... Severe thunderstorms are expected across the Carolinas and Mid Atlantic region later this afternoon and evening. A few severe thunderstorms are also possible across portions of southeast Alabama, southwest Georgia, and Florida. ...Middle Atlantic/Southeast... Late-evening water-vapor imagery depicts an expanding/thickening band of cloudiness across the Arklatex region, indicative of increasing large-scale ascent ahead of a strong short-wave trough. Intense mid-level height falls will spread across the Gulf States/TN Valley region during the day as 130kt 500mb speed max translates across northern AL into the southern Appalachians by 25/00z. While the surface reflection in response to this feature will not be particularly deep, a surface low should track north-northeast from GA into the eastern WV Panhandle by early evening. As this occurs, low-level trajectories will become more favorable for Atlantic moisture to advance inland across Coastal Carolinas as a warm front lifts to near the VA/NC border at 25/00z, then into the Delmarva later in the evening. This warm sector advancement will allow for modest destabilization that will support robust updrafts ahead of the surging cold front. Early in the period, a frontal squall line should be ongoing from AL to extreme southeast LA. This activity may be severe at daybreak, but higher buoyancy will be noted south of the FL Panhandle which may ultimately lead to the strongest storms gradually focusing offshore with time. However, by mid-late afternoon, instability should improve markedly along the SC/NC Coast as intense southerly low-level flow strengthens ahead of the short wave. Forecast soundings depict 1km flow on the order of 60kt with MUCAPE in excess of 1000 J/kg at ILM by evening. Intense shear and modest surface-based buoyancy suggest there is a concern for tornadoes with supercells later this afternoon/evening. Latest high res guidance support a considerable amount of pre-frontal warm-advection convection with supercell structures spreading inland by 21z. Otherwise, some tornado threat will be noted with embedded circulations along the frontal squall line. Damaging winds are also expected with the linear MCS as it spreads east. ..Darrow/Gleason.. 12/24/2020
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