Valid 231300Z – 241200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
…SUMMARY…
Expect isolated to widely scattered thunderstorms over part of the
Southeast.
…Synopsis…
The main mid/upper-level feature influencing convective potential
this period will be a cyclone now covering parts of MO, KS, OK, AR,
and IA, with embedded circulation centers evident over northern MO
and northeastern OK. The accompanying 500-mb trough is expected to
pivot eastward and northeastward through the period with some
amplification. By 00Z, the low should be located over southern/
eastern IN, with trough across middle TN and portions of AL/MS. By
12Z, the main vorticity maximum should reach southern PA, with
trough across VA, the Carolinas, GA, and the FL Panhandle.
Northwest flow aloft will extend far behind this trough, across the
Great Plains, central/northern Rockies and much of the Intermountain
region. A cut-off low will remain over the open Pacific around
600-700 nm west of northern Baja.
The surface low, associated with the central CONUS mid/upper trough,
was analyzed at 11Z near MSL, with cold front southwestward across
southern MS and southern LA to the northeast MX coastline south of
BRO. By 00Z, the low should reach the OH/WV border area, with cold
front across the western Carolinas, southwestern GA, and the
north-central Gulf. By 12Z, the low should redevelop across the
north-central Appalachians to the eastern NJ/NY City area. The cold
front will move offshore from all the Atlantic Coast except
northeastern FL, extending to west-central FL and the southwestern/
south-central Gulf. A marine/warm front — analyzed at 11Z over
southern AL, the western FL Panhandle and western FL peninsular
shelf waters – will move slowly northeastward while being overtaken
by the cold front and prefrontal convection.
…Southeast…
A band of widely scattered to scattered thunderstorms is possible
near the front, with isolated thunderstorms in the warm sector. A
few strong cells are possible, especially over portions of
southeastern AL, southern GA and the FL Panhandle. There, a narrow,
marginally buoyant sliver of surface-based inflow air may form near
or even slightly poleward of the marine boundary, with MLCAPE in the
100-400 J/kg range. Low-level and middle-level lapse rates will be
weak — barely larger than moist adiabatic in the mean, with shallow
layers of absolute stability possible. This will substantially
limit updraft vigor and mitigate the potential for severe
downdrafts, even in the presence of strong mid/upper winds and
conditionally favorable cloud-layer shear. The positively tilted
character of the mid/upper trough will render mean winds strongly
parallel to the front, making storm mode messy and mostly linear.
At this time, severe potential, while not zero, appears too low-end
in magnitude, and isolated in coverage, for a categorical area.
..Edwards/Kerr.. 11/23/2019
$$