Valid 111630Z – 121200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE SOUTHEAST…
Isolated damaging winds and a brief tornado are possible across
parts of the Southeast States this afternoon.
Split flow aloft will continue across the U.S. this period, with
northern-stream troughing to shift across the Great Lakes and into
the Northeast, while a second trough digs southeastward out of the
Canadian Rockies toward the north-central U.S. in its wake.
In the southern stream, a low/trough currently residing over the
southwestern deserts and adjacent northwestern Mexico will advance
slowly eastward to the southern Rockies/southern High Plains, while
downstream ridging amplifies in response over the Southeast.
At the surface, a cold front extending from a weak low over the Mid
Atlantic region west-southwestward to Deep South Texas will progress
steadily southeastward while weakening. Farther north, a
second/polar cold front is forecast to shift southeastward out of
the Canadian Rockies/Prairie Provinces into north-central portions
of the CONUS.
…Southeast Virginia to central Alabama…
Ahead of a cold front gradually shifting southeast of the
Appalachians, a moist warm sector is indicated — though weak lapse
rates aloft continue to limit available CAPE. This — combined with
weak convergence along the front and a general lack of appreciable
surface heating suggest that frontal convection will remain
generally limited in intensity despite amply
strong/west-southwesterly flow aloft.
As a very weak/subtle short-wave trough shifts across the Southeast
today, a modest/relative diurnal peak in convective activity is
expected. A few of the strongest updrafts may prove capable of a
locally stronger wind gust or two, and a brief/weak tornado cannot
be ruled out as well. However, any risk appears to remain limited,
and should diminish from west to east as the subtle upper feature
crosses the region and short-wave ridging — and associated
subsidence — increases in its wake.