Valid 052000Z – 061200Z
…THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL/NORTHERN MS AND NORTHWESTERN AL…
Severe thunderstorms are expected this afternoon through tonight
across portions of the lower Mississippi Valley and Southeast, with
a few tornadoes, damaging wind gusts, and large hail all possible.
Mainly elevated supercells have produced several large hail reports
across parts of western and northern LA over the past few hours.
Additional storms have recently begun to increase in intensity
across southern LA/MS in a strengthening low-level warm advection
regime. With 1000-1500 J/kg of MLCAPE and 50 kt of effective bulk
shear present, these storms will likely continue to display
supercell characteristics. All severe hazards appear possible with
this convection. For more information on the near-term severe risk
across this area, see Mesoscale Discussion 77.
Otherwise, a surface low should gradually deepen through the
remainder of the afternoon and into this evening as it develops
northeastward from the LA/MS border to the TN Valley. Surface
pressure falls around 3-4 mb in the past two hours are preceding
this low over central/northern MS and northern AL. Low-level flow
has backed to south-southeasterly mainly across central MS in
response. A narrow corridor extending southwest to northeast across
this region should remain the most favorable for supercells capable
of producing a few tornadoes through this evening. Based on
short-term model guidance and observational trends, it still appears
that some of these tornadoes could be strong. See Mesoscale
Discussion 78 for more information on the near-term severe threat
for this region.
.PREV DISCUSSION… /ISSUED 1019 AM CST Wed Feb 05 2020/
…Lower MS into TN Valley…
Morning water vapor imagery shows a strong upper trough digging
across the southern Plains. In the low-levels, a deepening surface
low currently over LA will track northeastward along the front into
parts of MS and northwest AL this afternoon and evening. The air
mass in the warm-sector has become quite moist with dewpoints in the
mid/upper 60s, with forecast soundings suggesting afternoon MLCAPE
values around 1500 J/kg. Given the increasing forcing mechanisms,
this should be sufficient for scattered thunderstorm development in
vicinity of the low and front.
12z CAM solutions suggest that convection will first form over
central LA as the large-scale forcing approaches. Low-level
vertical shear will promote some risk of discrete supercells, along
with more complex bowing structures. Forecast hodographs indicate
favorable parameters for a few tornadoes, including the risk of
strong tornadoes, as activity builds northeastward across the ENH
risk area. Damaging wind gusts and perhaps some hail are also
possible in the strongest cells.
Later tonight, another round of severe storms appears likely to form
along/ahead of the front across the remainder of the SLGT risk area.
Models are more diverse regarding timing/placement of this activity,
but sufficient vertical shear will pose a risk of a few supercells
capable of damaging winds and isolated tornadoes.