Day 1 Severe Weather Outlook

Valid 211200Z – 221200Z


Severe thunderstorms are possible beginning Monday morning from the
lower Mississippi Valley to the central Gulf Coast, accompanied by a
risk for damaging wind gusts and perhaps a tornado or two.

An upper low will deepen as it moves from NE to WI, with an
extensive, cyclonically curved jet max extending from north TX to
the OH Valley to MI by 00Z. Significant height falls will occur
across the MS and OH Valleys as a cold front moves toward the TX
Coast and TN/OH Valleys by late afternoon. Ahead of this front, a
plume of rich boundary-layer moisture will exist, with severe storms
possibly ongoing at the beginning of the period from east TX to the
lower OH Valley.

As the system occludes over the upper MS Valley during the day, the
pre-frontal moist plume will constrict from north to south, with
northern tip of the 60s F dewpoints translating east/southeastward
across MS, southern AL and the FL Panhandle. Drier air will remain
over the Appalachians, likely reducing severe potential as the front
continues east into GA overnight.

…Lower MS and OH Valleys…central Gulf Coast…
An extensive line of thunderstorms will be ongoing along the cold
front early Monday morning, from IL to east TX. Damaging winds or a
brief tornado will be possible with these linear storms, owing to
sufficient CAPE in place and effective SRH over 300 m2/s2. As the
moist plume narrows to the north, the greatest threat for the rest
of the day will be over LA and MS where upper 60s to low 70s F
dewpoints will maintain MLCAPE of at least 500 J/kg, despite
relatively warm midlevel temperatures and limited heating. Still,
veering winds with height with effective SRH around 200 m2/s2 may
support a supercell with a brief tornado or damaging wind gust.

Later in the day and through the evening, southerly surface winds
will bring low to mid 70s F dewpoints northward across southern AL
and the FL Panhandle. This may support a few strong storms as the
front continues east, beneath 50 to 60 kt mid to upper flow.

..Jewell/Squitieri.. 10/21/2019


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