Valid 302000Z – 011200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
ARKLATEX TO LOWER MS VALLEY AND MID-SOUTH…
…SUMMARY…
Scattered severe thunderstorms are expected through this evening
across the Arklatex, Lower Mississippi Valley, and Mid-South
regions. A couple tornadoes, large hail, and damaging winds are
anticipated.
…20Z Update…
…Arklatex into the Lower MS Valley and Mid-South…
19Z surface analysis places the cold front from southeast MO
southwestward across central AR and central TX. Storms along the
front as well as those within the pre-frontal warm sector have
struggled to develop deep updrafts thus far. However, recent radar
trends suggest storm strength is increasing within the pre-frontal
storms across east-central TX and northwest LA as well as those
along the front in central TX. Given the strong deep-layer shear,
any of the more robust and persistent pre-frontal updrafts should be
able to organize into supercells, with an attendant wind
damage/tornado threat for the next several hours.
Along the front, the progressive nature of the boundary will lead to
undercutting but a few strong wind gusts are still possible as
frontal circulations augment updrafts and downdrafts.
As mentioned in the previous outlook (appended below), reduction in
the instability with eastern extent should lead to a diminishing
trend in storm intensity and coverage.
..Mosier.. 11/30/2019
.PREV DISCUSSION… /ISSUED 1030 AM CST Sat Nov 30 2019/
…Arklatex to Lower Mississippi Valley and Mid-South…
At late morning, a northeast/southwest-oriented broken band of
occasionally strong/locally severe convection continues to progress
east-southeastward across west-central Arkansas/northeast Texas. A
band/wave-like feature precedes this convection by about 70-80
miles, and this could also be a factor for renewed thunderstorm
development/intensification this afternoon across the ArkLaMiss
region. For short-term expectations, reference Mesoscale Discussion
2177.
Aided by a 50 kt southwesterly low-level jet ahead of the front, a
corridor of upper 60s F surface dew points across east Texas will
continue to advect east-northeastward across Louisiana and far
southern Arkansas this afternoon, with a bit more modest
moistening/destabilization expected this evening eastward into
Mississippi/western Tennessee. An instability-limiting aspect will
be that cloud cover/stratus may tend to persist within the warm
sector, which will likely result in sub-optimal parcel accelerations
and probably curb the overall magnitude of today’s severe risk.
Regardless, a diurnal destabilization trend will occur and
deep-layer shear will strengthen as a powerful mid-level jet (100
kt) amplifies over the southern Plains and Ozarks. These factors
will aid in increasing convective intensity/organization this
afternoon, particularly across far northeast Texas, northern
Louisiana and southern/eastern Arkansas and eventually into
Mississippi. Deep-layer/low-level shear will be more than adequate
for both supercells and well-organized bands capable of damaging
winds and a couple of tornadoes. While mid-level lapse rates are not
steep, favorable hodographs and somewhat modest forcing/sufficiently
favorable convective mode will support the possibility of large
hail.
Overall severe threat should wane with eastern extent across the
Tennessee Valley tonight given a diminishing trend of surface-based
instability.
$$