SPC 0830Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0210 AM CST Mon Dec 14 2020

Valid 161200Z - 171200Z


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

Little change in the general large-scale pattern is expected from
Tuesday into Wednesday.  Stable conditions will prevail across much
of the U.S., except along a northwestward sloping frontal zone
extending across the middle and southern Atlantic Seaboard into the
northeastern Gulf of Mexico.  Aside from parts of northern
Florida/the northern Florida Peninsula, the surface front is
expected to mostly remain offshore.  However, moisture return above
the frontal inversion, inland of coastal areas, may contribute to
areas of very weak CAPE.  This may contribute to at least low
probabilities for convection capable of producing lightning, as a
vigorous remnant short wave perturbation rapidly accelerates
northeast of the lower Mississippi Valley.

Initially, there may be a couple of developing waves along the
frontal zone, one over the northeastern Gulf of Mexico and another
off the South Carolina coast.  However, as the mid-level
perturbation approaches the Mid Atlantic coast, the trailing wave is
expected to weaken as the lead wave becomes more prominent. 
Substantive further deepening is forecast as a developing cyclone
center tracks near or across the North Carolina Outer Banks vicinity
into areas off the Mid Atlantic coast by Wednesday evening.

...Eastern North Carolina...
There appears at least some possibility that the track of the
developing 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, it probably will
be in the presence of wind profiles characterized by strong
deep-layer shear and sizable, clockwise curved low-level hodographs,
supportive of supercell convection posing potential to produce a
tornado or damaging wind gusts.

...Northern Florida/Florida Peninsula...
A signal exists in the latest model output that a cluster of
thunderstorms will spread into coastal areas by Wednesday afternoon.
Initially supported by moderate boundary-layer CAPE over the
northeastern Gulf of Mexico, an organized line of vigorous
thunderstorms may develop along the leading edge of this cluster, in
the presence of sheared, 30-50+ kt west-southwesterly deep-layer
mean flow.  Although the environment may become progressively less
stable into coastal areas, with instability inland also remaining
poor, it is possible that a damaging wind/isolated tornado risk
could at least develop into coastal areas between Tampa and the Big
Bend vicinity, before diminishing.

..Kerr.. 12/14/2020

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