Convective Outlook

Day 2 - Storm Prediction Center Norman, Oklahoma

ACUS02 KWNS 130555
SPC AC 130554

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1154 PM CST Wed Dec 12 2018

Valid 141200Z - 151200Z


Severe thunderstorms are possible across central and northern
Florida into adjacent southeastern Georgia Friday into Friday night.
Additional strong storms may impact the Carolina coastal plain,
accompanied by at least some risk for severe weather.

Much of the nation will remain under the influence of split belts of
westerlies emanating from the mid-latitude Pacific, and the
subtropical eastern Pacific.  Several waves embedded within the
mid-latitude westerlies appear likely to remain amplified through
this period, including a couple progressing through one branch
across the Pacific Northwest into the Canadian Prairies.  A much
more prominent perturbation within a branch to the south, including
a deep lower/mid-tropospheric cyclone, may also remain progressive,
but more slowly, across and east/northeast of the lower Mississippi

In association with this latter system, increasingly moist air,
emanating from a more substantively modifying boundary layer over
the central/eastern Gulf of Mexico, appears likely to continue to
wrap into the cyclone.  At the same time, highest moisture content
likely will advect northeastward in a plume across much of the
southern and mid Atlantic Seaboard.  This may include mid/upper 60s
surface dew points within the warm sector of a developing secondary
surface wave, across much of Florida and adjacent southeast Georgia
into the Carolina coastal plain.

Destabilization associated with the moistening, coupled with
large-scale ascent associated with the cyclone and mid/upper wave,
likely will support considerable convection and embedded
thunderstorm activity Friday through Friday night.  It appears that
this will include a risk for severe storms.

Considerable spread remains evident within model ensemble output,
and among the various deterministic model output, concerning the
evolution and progression of the cyclone, including possible
secondary surface wave development inland across western/northern
Florida into the Carolinas.

Boundary layer destabilization, and convective development
accompanied by some severe weather potential, may not be entirely
out of the question in the residual warm sector near the triple
point of the occluding primary cyclone, over parts of northeastern
Mississippi into northern/central Alabama Friday afternoon.
However, at the present time, uncertainties concerning this risk
remain large, and severe weather probabilities still appear less
than 5 percent.

Otherwise, severe weather potential appears a little more certain
across central and northern Florida.  Whether this risk maximizes
early in the day Friday, or later, during the afternoon and evening,
appears the primary uncertainty, due to the spread concerning the
progressiveness of the mid-level low.

Inland boundary layer destabilization may remain modest to weak
(including CAPE on the order of 500 J/kg), but in the presence of
strengthening wind fields and shear, this is expected to be
sufficient to contribute to severe weather potential with organized
convection spreading inland off the Gulf of Mexico.  This probably
will coincide with the inland progression of the secondary surface
frontal wave, beneath the leading edge of the difluent, cyclonic
mid/upper flow.  Convection could include a broken line or two, as
well as discrete supercells.  Damaging wind gusts may be the primary
hazard, but low-level hodographs could become large enough to
support a risk for tornadoes as well.

As the frontal wave/low develops northeastward into the Carolinas,
it appears possible that boundary layer destabilization may become
supportive of a risk for severe storms across the coastal plain.
However, the extent of this threat remains at least a bit unclear at
the present time.

Tornado:   5%     - Slight
Wind:     15%     - Slight
Hail:      5%     - Marginal

..Kerr.. 12/13/2018