Mesoscale Discussion 0228
NWS Storm Prediction Center Norman OK
0234 PM CDT Tue Mar 24 2020
Areas affected...Parts of southwestern into middle
Tennessee...northestern Mississippi and northwestern Alabama
Concerning...Severe potential...Watch likely
Valid 241934Z - 242130Z
Probability of Watch Issuance...80 percent
SUMMARY...The risk for severe thunderstorms is expected to increase
during the next few hours. By 5-7 PM CDT, this probably will
include potential for supercells capable of producing tornadoes,
particularly near/northeast of Tupelo MS into areas near and
northwest of Muscle Shoals AL, Huntsville AL and the Shelbyville,
Tullahoma area of southern Middle Tennessee.
DISCUSSION...As one weakening mid-level jet streak continues to
propagate across the Mid South, toward the southern Appalachians,
the exit region of another (70+ kt at 500 mb) is forecast to dig
east-southeast of the Ark-La-Tex through central Mississippi by
23-00Z. As this occurs, weak to modest mid-level height falls
appear likely to overspread a destabilizing boundary layer, along
and south of a surface frontal zone now near/just north of Memphis
TN, Muscle Shoals and Huntsville AL.
Insolation and surface dew point increases through the lower/mid 60s
appear to be contributing to mixed-layer CAPE in excess of 1000
J/kg, with remaining inhibition becoming increasingly negligible.
In the presence of strong deep-layer shear, the environment is
becoming conducive to organized severe thunderstorm development,
including discrete supercells. While the front may become a focus
for this convective development, model output suggests additional
discrete storm development is possible along the low-level jet axis
extending southward across at least much of northern Mississippi.
As a weak frontal wave redevelops eastward from parts of northern
Arkansas into northern middle Tennessee, the latest Rapid Refresh
forecast soundings continue to suggest that low-level hodographs
will become most conducive to tornadic supercells near/northeast of
Tupelo MS, into the Muscle Shoals and Huntsville TN vicinities, and
areas near/west of Tullahoma TN by 5-7 PM CDT. This will include
potential for an isolated strong tornado or two.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 34598984 35378927 35798794 35588630 34708659 33798852