Valid 242000Z – 251200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE EASTERN
A tornado or two and isolated damaging winds are possible this
evening through tonight across the eastern Carolinas.
Recent surface analysis places an elongated area of low pressure
over the western Carolinas. Downstream surface pressure falls are
maximized across central NC, indicating a general northeastward
motion of this low will likely continue. Further deepening is
anticipated with a more coherent low eventually developing this
evening. Southerly/southeasterly low-level flow is expected to
persist, resulting in continued moisture advection ahead of this
developing low and attendant cold front.
Showers and thunderstorms are still expected to develop within this
warm sector. As mentioned in the previous outlook (appended below),
buoyancy remains the limiting factor. Most recent guidance brings
low 60s dewpoints into southeast NC, which seems reasonable given
the southeasterly surface winds and recent buoy observations of low
60s dewpoints just offshore. However, even with low 60s dewpoints
the air mass only modestly destabilizes (i.e. MLCAPE around 500-800
Given the combination of modest instability and strong vertical
shear, a few low-topped supercells capable of damaging wind gusts
and a brief tornado or two are possible, mainly across eastern SC
into southeast NC.
.PREV DISCUSSION… /ISSUED 0952 AM CST Fri Jan 24 2020/
No changes have been made to inherited Marginal Risk.
A closed mid-level low and attendant surface cyclone over the Mid-MS
Valley will gradually move northeast and occlude towards southern
Lake MI. Secondary weak cyclogenesis will occur across the Piedmont
of NC/VA tonight in advance of an embedded mid-level speed max
progressing eastward from the Gulf Coast States to the Carolinas.
Some increase in low-level moisture is expected across the South
Atlantic Coastal Plain in response to southerly low-level flow from
the FL East Coast and gradual erosion of a currently cool air mass
inland. Surface dew points should only reach around 60 F with mean
mixing ratios approaching 11 g/kg, yielding a plume of weak MLCAPE
from 250-750 J/kg across the Savannah Valley to southeast NC
Convergence along/just ahead of the cold front trailing from the
slowly deepening surface cyclone will increase this evening and
persist as a zone of focused ascent through tonight. A band of
generally elevated convection is expected to form across central NC
with trailing portion towards coastal SC becoming surface-based,
shifting east through the night. Deep-layer vertical shear will
favor the potential for a couple embedded supercells, but the
limited buoyancy will likely preclude greater sustainable coverage.
Low-level hodographs will be adequate for a tornado or two, along
with isolated damaging winds, mainly across eastern SC into