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ACUS11 KWNS 242029
SWOMCD
SPC MCD 242028
ARZ000-TXZ000-OKZ000-242300-

Mesoscale Discussion 0232
NWS Storm Prediction Center Norman OK
0328 PM CDT Sun Mar 24 2019

Areas affected...Portions of eastern OK...northeast TX...and much of western/central AR

Concerning...Severe potential...Watch likely

Valid 242028Z - 242300Z

Probability of Watch Issuance...80 percent

SUMMARY...Increasing severe threat this afternoon and evening will
likely require watch issuance by 22-23Z (5-6 pm CDT). Large hail and
damaging winds should be the main threats.

DISCUSSION...Surface temperatures have warmed into the low to mid
70s across eastern OK ahead of a slow moving cold front. Even though large-scale forcing for ascent should remain modest, convective
inhibition has mostly eroded this afternoon over parts of eastern
OK, western AR, and northeast TX as low-level moisture has gradually
increased across the warm sector. Some increase in cumulus
development has recently occurred in east-central OK per recent
visible satellite imagery, and an attempt at convective initiation
is underway in Cherokee County OK as of 2025Z. As a weak cap
centered around 790 mb on the 18Z SGF sounding continues to slowly
erode, additional attempts at convective initiation appear
increasingly likely by 22Z (5 pm CDT) along the cold front in
eastern OK/western AR.

Some steepening of mid-level lapse rates to around 7 C/km has
occurred across this region, which along with the gradually
increasing low-level moisture and daytime heating is contributing to
500-1000 J/kg of MLCAPE at 20Z. Instability may potentially reach
the 1000-1500 J/kg range by peak heating based on several RAP
forecast soundings. Strengthening westerly flow above 3 km is
supporting 40-50 kt of effective bulk shear, and supercells will
probably be the dominant storm mode initially. Given the long,
mostly straight hodographs noted on forecast soundings across this
region, large hail appears likely with any supercell that can form
along/ahead of the front. Isolated damaging winds may also occur
where low-level lapse rates can steepen and act to accelerate
convective downdrafts. Low-level winds are generally veered to
southwesterly and relatively weak (less than 25 kt at 850 mb).
Accordingly, the tornado threat will probably remain limited, but it
is not zero.

Short-term CAM guidance suggests that greater storm coverage may be
realized from the vicinity of Fort Smith, AR into far southeastern
OK, west-central into southwestern AR, and perhaps northeast TX
through this evening where relatively greater instability should be
present. Regardless, the increasing severe threat across this region
will likely require watch issuance in the next couple of hours.

..Gleason/Hart.. 03/24/2019

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

ATTN...WFO...LZK...SHV...TSA...FWD...OUN...

LAT...LON 35449487 36489378 36479087 35399139 33959267 33179393
32989473 32889540 32889595 32999646 33299668 33909628
35449487



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