SPC MD 1621


MD 1621 Image

Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0338 PM CST Mon Nov 05 2018

Areas affected...northern Louisiana...eastern Arkansas...northern
Mississippi and western Tennessee

Concerning...Severe potential...Watch likely 

Valid 052138Z - 052345Z

Probability of Watch Issuance...80 percent

SUMMARY...Storms are expected to increase in coverage mainly after
23-00Z across northern Louisiana and eastern Arkansas, and will gain
strength as they develop eastward into northern Mississippi and
Tennessee during the evening. Damaging winds and tornadoes will be

DISCUSSION...The air mass across east TX and the lower MS Valley
continues to destabilize via both low-level theta-e advection
associated with a warm front, and mixing of the boundary layer aided
by pockets of heating. As of 21Z, the most unstable air was located
over southeast TX, where 70s F dewpoints and strong heating exist.

18Z soundings indicate a substantial midlevel inversion which is
limiting instability. This inversion will weaken somewhat this
evening as a strong jet max noses into AR, northern MS and western
TN, providing cooling aloft.

Currently, scattered convective showers exist near the instability
axis over east TX and northwest LA, but they are shallow with no
lightning due to the warm midlevel temperatures. However, they are
already rotating. Farther north, a band of ascent was evident on
radar from the ArkLaTex into central AR, with gradually warming
temperatures south of that area. 

Over the next several hours, both these areas will likely
consolidate into thunderstorms across northern LA and southern AR,
and may mature into northern MS and western TN this evening. Shear
profiles will continue to increase as the low-level jet intensifies
to over 50 kt. Hodographs will strongly favor supercells,
potentially tornadic, but storms may eventually transition to a
QLCS. Therefore, both damaging winds and tornadoes will be possible.
The greatest threat is likely to exist east of the MS river and
after 03Z, when lift, shear, and low-level moisture are maximized.

..Jewell/Thompson.. 11/05/2018

...Please see www.spc.noaa.gov for graphic product...


LAT...LON   32719056 32259196 31919297 31779346 31789375 32059397
            32339384 34239146 34999072 35349027 35538956 35448887
            35128851 34618835 34378839 33368946 32719056 

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