...20Z Update...
No changes have been made to the Moderate Risk area. Convection is
beginning to increase in coverage and intensity ahead of the cold
across far east TX, in addition to the ongoing activity along the
front itself. As a southerly low-level jet strengthens late this
afternoon into this evening, a corresponding increase in effective
SRH will likely lead to greater tornado potential with time. The
greatest threat for strong tornadoes remains apparent this evening
across parts of northern LA into southern/eastern AR,
northern/central MS, and western/middle TN. This will especially be
the case with any supercells that can remain discrete ahead of the
line.
A bowing line/MCS will likely develop this evening as convection
grows upscale along/ahead of the front. The northern extent of
appreciable severe threat will likely be constrained by a
convectively reinforced outflow boundary from thunderstorms earlier
today that currently extends from parts of AR into TN. This boundary
will attempt to lift back northward this evening and overnight as a
surface low deepens from the Mid-South into the lower OH Valley.
Still, the threat for damaging winds and tornadoes should become
increasingly limited with northward extent into KY and the OH
Valley.
The primary change with this update was to expand severe wind
probabilities and corresponding categorical lines a bit eastward
across AL/TN, north GA, and western NC/SC. Recent high-resolution
guidance, including multiple runs of the HRRR, suggest that a
well-organized bow will continue eastward across these areas late
tonight into early Saturday morning. Although instability is
forecast to remain weak, very strong low-level shear associated with
a 55-65+ kt low-level jet should allow the line to remain organized
and pose a continued threat for severe/damaging winds and a few
embedded QLCS tornadoes.
