SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1200 AM CST Sat Nov 21 2020 Valid 221200Z - 231200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms appear unlikely across the contiguous United States on Sunday. ...Synopsis and Discussion... An upper trough initially over the Plains and Upper Midwest Sunday morning will progress eastward across the MS/OH Valleys to the eastern states by the end of the period. At the surface, a weak low over the mid MS Valley should develop northeastward across the OH Valley and into the Mid-Atlantic/Northeast by late Sunday night while slowly deepening. A cold front attendant to this surface low is forecast to sweep east-southeastward across much of the southern Plains, lower MS Valley/Southeast, and eastern states through early Monday morning. Limited low-level moisture, characterized by 50s surface dewpoints, should be present in a narrow corridor ahead of the front across parts of TX to the Mid-South. Isolated showers and thunderstorms may be ongoing at the start of the period over these areas along/behind the front, although instability should remain rather weak owing to poor mid-level lapse rates. Thunderstorm potential should quickly diminish by Sunday afternoon as the forcing associated with the upper trough departs this region. Negligible instability forecast across the OH Valley/Mid-Atlantic suggests thunderstorm potential should remain very low as the upper trough moves over these areas. Along much of the East Coast, surface ridging should generally hinder the inland advance of substantial low-level moisture. One exception may be eastern NC/SC late Sunday night into early Monday morning. Here, upper 50s to low 60s surface dewpoints may be present ahead of the eastward-advancing cold front. As modest mid-level height falls associated with the approaching upper trough overspread this region, at least isolated thunderstorms may develop. Although deep-layer shear appears sufficient to support organized storms, current expectations are for greater instability to remain confined to immediate coastal areas, with any meaningful strong to severe storm potential probably remaining offshore. Elsewhere, isolated thunderstorms may occur Sunday across parts of the FL Peninsula and the Keys as weak low-level easterly flow continues, and the Four Corners vicinity into western CO as upper troughing amplifies over the western CONUS late in the period. ..Gleason.. 11/21/2020
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