SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1210 AM CST Sun Nov 29 2020 Valid 301200Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS FAR SOUTHEAST VA AND COASTAL NC... ...SUMMARY... Isolated strong to severe thunderstorms capable of producing damaging winds and perhaps a couple of tornadoes appear possible on Monday from parts of Florida and coastal Georgia into the Carolinas and Mid-Atlantic. ...Synopsis... A deep upper trough is forecast to extend from eastern Ontario into the Lower MS Valley early Monday morning. An embedded shortwave trough will likely be centered over the southern Appalachians, with another shortwave trough in its wake centered over the Ozark Plateau. Quick northeastward progression is anticipated by the lead wave with the Ozarks shortwave digging southward and then eastward across the Southeast. This pattern evolution will be accompanied by strengthening low to mid-level flow and cyclogenesis. By the end of the period, a mature mid-latitude cyclone will likely be centered over the central Appalachians, with strong, deep-layer flow extending throughout its eastern periphery along the East Coast. Surface low associated with this cyclone is forecast to begin to the period over the central Appalachians with a cold front extending southward/south-southwestward to the FL Big Bend. This surface low is then expected to move north-northeastward and become increasingly occluded throughout the day. At the same time, the attendant cold front will sweep eastward off the East Coast. ...Much of the East Coast... Dewpoints in the low 60s will likely extend as far north as the VA Tidewater region early Monday morning. Mid to upper 60s dewpoints are expected to be in place farther south across southeast GA and most of FL, with mid 50s dewpoints extending up into the Delmarva. The overall environment ahead of the cold front will be characterized by abundant cloud cover, moist profiles and poor mid-level lapse rates. Even so, the modest low-level moisture is expected to result in limited instability and the potential for a few deeper updrafts capable of either damaging wind gusts and/or brief tornadoes. This potential severe threat will exist along the length of the front, from the Mid-Atlantic into FL, but the threat appears to be maximized over coastal NC Monday morning. In that area, southerly/south-southeasterly surface winds beneath strong (i.e. 50-55 kt) 850-mb winds will result in low-level kinematic profiles very supportive of rotation. Previously mentioned limited instability will result in predominantly transient updrafts, particularly ahead of the front in warm sector, with limited depth and persistence. However, any deeper, more persistent updrafts may be able to produce damaging wind gusts and/or a tornado or two. Farther north (from the Delmarva into coastal southern New England), the primary severe threat will be later into the afternoon as the triple point moves across the region. Low probability potential exists for the development of a narrow and shallow line of convective along the cold front extending southward from the triple point. Even less instability is anticipated here than farther south and any convection will likely become elevated above a low-level stable layer, but the very strong wind fields suggest than even a shallow, elevated storm may be able to produce a strong gust at the surface. ..Mosier.. 11/29/2020
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