Valid 111200Z – 121200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
Severe thunderstorms are not expected Wednesday.
A large-scale mid-level trough will move off of the Atlantic
Seaboard today, with high pressure ushering in behind a cold front
across much of the central and eastern CONUS. Farther west, a
mid-level shortwave trough will traverse the Rockies into the Plains
states by the end of the period, with a more potent mid-level wave
and associated surface trough approaching the Pacific Northwest.
The trailing portion of a cold front will gradually move
southeastward across the Florida Peninsula, where at least modest
instability (up to 1000 J/kg MLCAPE in spots) will be in place.
Convergence along the cold front, coupled with diurnal heating, will
encourage at least isolated thunderstorm development through the
late morning and afternoon hours.
…Louisiana/Mississippi Coastline and adjacent waters…
Despite the passage of the surface front, 850 mb frontogenesis will
support banded-precipitation, perhaps with a few convective elements
along and just offshore the Louisiana/Mississippi Coastlines. Though
instability is quite meager, enough elevated MUCAPE in the -20 to
-30C layer may support a couple lightning strikes early in the
…Portions of the Washington Coastline…
The approach of the aforementioned mid-level wave later in the
period will result in steepening mid-level lapse rates (7.5 C/km)
across portions of the Washington Coastline and adjacent waters.
Here, deep-layer ascent will also increase with the approach of a
surface trough by 00Z. Multiple guidance members hint at some
instability across the area, with the 03Z RAP being the most
aggressive member (depicting up to 400 J/kg MUCAPE). In addition,
adequate deep-layer and low-level shear may support an isolated gust