...Southeast...
Greatest confidence in substantive boundary layer moistening still
appears across portions of the eastern Gulf states into the south
Atlantic Coast states. Vigorous convective development may be
ongoing at 12Z Wednesday inland of the northeast Gulf coast, in
response to destabilization associated with the moistening, and
large-scale ascent associated with low-level warm advection. Models
are suggestive that forcing for this activity will be aided by a
high-level subtropical speed maximum, which may contribute to an
increase in coverage through the day, within the northeastward
advecting plume of richer precipitable water content.
In the presence of at least modestly steep mid-level lapse rates,
and wind profiles becoming characterized by strong deep layer shear
and sizable low-level hodographs, considerable organized severe
weather potential appears to exist. This is expected to include
discrete supercells accompanied by the risk for large hail and
tornadoes. In the wake of initial convective development expected
to spread northward across and to the lee of the southern
Appalachians during the day, guidance suggests new discrete storm
development is possible within a low-level confluence zone across
southern/eastern Alabama into western Georgia, with the environment
ahead of this activity possibly becoming conducive to long-lived
supercells with potential for strong tornadoes.
Additional pre-frontal storm development is also possible to the
west of this activity Wednesday afternoon into Wednesday evening.
...Ohio/Tennessee Valleys...
Confidence is increasing in warm sector moisture return that will
become supportive of weak to moderate CAPE, within at least a narrow
pre-frontal plume overspreading the region from west to east
Wednesday afternoon and evening. Aided by forcing within the exit
region of a 70-90 kt cyclonic 500 mb jet, and strengthening of
southerly 850 mb flow to 30-50 kt within the warm sector, the
environment is expected to become conducive to discrete supercell
storm development, at least initially. This is expected to be
accompanied by a risk for large hail and a few tornadoes, some of
which could be strong. Eventually, large-scale forcing may support
upscale growing lines or clusters of storms accompanied by a more
substantive risk for damaging wind gusts
