SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1148 PM CST Mon Dec 14 2020 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS PARTS OF EASTERN NORTH CAROLINA AND GULF COASTAL PORTIONS OF THE NORTHERN FLORIDA PENINSULA... ...SUMMARY... Strong thunderstorms may impact parts of the Outer and Inner Banks vicinity of North Carolina and Gulf coastal areas of the northern Florida Peninsula Wednesday, posing at least some risk for severe weather. ...Synopsis... As mid/upper flow continues to trend more zonal across Canada, a broad west-northwesterly belt of westerlies emanating from the mid-latitude Pacific will maintain considerable influence across much of the U.S. through this period. This regime will include a number of short wave troughs progressing inland of the Pacific coast, and across and east of the Rockies. However, stable conditions present across much of the nation are expected to generally be maintained, to the north and west of a broad northwestward sloping frontal zone initially extending across the middle and south Atlantic Seaboard into the northern Gulf of Mexico. Aside from portions of northern Florida, the surface front is still expected to be offshore. However, models indicate that low-level moisture return will be ongoing above the frontal inversion, inland of coastal areas, ahead of a vigorous remnant mid-level perturbation rapidly accelerating northeast of the lower Mississippi Valley. This may at least initially include a 90-100 kt 500 mb jet streak. As the mid-level perturbation approaches the Mid Atlantic Coast region during the day, associated large-scale forcing for ascent and elevated moisture return may contribute areas of very weak CAPE, and perhaps thermodynamic profiles supportive of scattered convection capable of producing lightning. At the same time, one initial surface frontal wave is expected to weaken while migrating inland off the northeastern Gulf of Mexico, through northern Florida, as another, initially off the South Carolina coast, undergoes considerable deepening. The center of the developing cyclone may migrate inland across parts of the North Carolina coastal plain by late Wednesday afternoon, before redeveloping east of the Mid Atlantic coast Wednesday night. ...Eastern North Carolina... Due to lingering spread among the output of the various models, the extent of severe weather potential for Wednesday remains at least somewhat unclear. It still appears that the track of the deepening surface cyclone may allow for at least a weakly destabilizing warm sector boundary layer to overspread the Outer and Inner Banks vicinity by Wednesday afternoon. If this occurs, deep-layer wind fields and shear probably will become sufficiently strong to support a risk for organized severe convection. The 15/00Z NAM forecast soundings for the Morehead City and Cape Hatteras vicinities (around the 16/21-23Z time frame) exhibit wind profiles characterized by strong deep-layer shear and very large clockwise curved low-level hodographs, which appear favorable for supercells capable of producing a strong tornado. Output from other models doesn't appear quite as favorable, but this will be monitored in later outlooks for this time period. ....Northern Florida/Florida Peninsula... Models continue to suggest that the environment over the northeastern Gulf of Mexico could become supportive of an organized cluster of storms by 12Z Wednesday. It appears that this will advect into coastal areas between Tampa and the Big Bend during the day, in the presence of 30-50 kt west-southwesterly deep-layer mean flow. Although inflow into a potentially vigorous leading line probably will become characterized by progressively weaker CAPE across the coastal waters and inland, there still appears at least some potential that this activity could be accompanied by a risk for damaging wind gusts and/or a tornado or two into coastal areas before diminishing. ..Kerr.. 12/15/2020
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