ZCZC SPCSWOMCD ALL
ACUS11 KWNS 211651 
SPC MCD 211651 
MSZ000-TNZ000-ARZ000-LAZ000-TXZ000-211915-

Mesoscale Discussion 1773
NWS Storm Prediction Center Norman OK
1151 AM CDT Tue Sep 21 2021

Areas affected...portions of central and southern Arkansas into
western Mississippi

Concerning...Severe potential...Watch unlikely 

Valid 211651Z - 211915Z

Probability of Watch Issuance...20 percent

SUMMARY...A couple damaging gusts may accompany the stronger storms.
A WW issuance is not expected given the anticipated isolated, brief
nature of the severe threat.

DISCUSSION...Thunderstorms have been increasing in number and
intensity along the cold front given low-level convergence and ample
diurnal heating. Surface temperatures in the mid to upper 80s F,
coupled with mid to upper 70s F dewpoints, are currently
contributing to 1000-2000 J/kg MLCAPE despite the relative absence
of appreciable lapse rates. However, as diurnal heating promotes
further heating and boundary-layer mixing, low-level lapse rates
should steadily improve through the afternoon, with further
increases in MLCAPE expected. 

A few ongoing storms have already shown up to 35 dBZ cores exceeding
60 kft, and with increasing instability, a greater number of deeper
water-loaded cores are expected. Despite the overall lack of robust
upper support and vertical wind shear ahead of the front,
water-loaded cores may support a couple of damaging gusts through
the afternoon. Nonetheless, given poor shear and brief,
pulse-cellular storm modes, the severe threat is expected to remain
sparse and brief, and a WW issuance appears unlikely.

..Squitieri/Hart.. 09/21/2021

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

ATTN...WFO...MEG...JAN...LZK...SHV...

LAT...LON   33219453 34329332 34929224 35129125 35069027 34808974
            34208943 33858941 33218970 32849017 32669086 32669196
            32839375 33219453 

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