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ACUS11 KWNS 302134
SWOMCD
SPC MCD 302134
ARZ000-LAZ000-TXZ000-OKZ000-302330-

Mesoscale Discussion 1667
NWS Storm Prediction Center Norman OK
0334 PM CST Fri Nov 30 2018

Areas affected...northeast Texas...southeast Oklahoma...western
through central Arkansas and northwest Louisiana

Concerning...Severe potential...Watch possible

Valid 302134Z - 302330Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms should undergo a gradual increase in
coverage and intensity over the Arklatex region through about 00Z,
with a more substantial severe threat expected to evolve after 01Z.
While a tornado watch is possible in the short term (next 1-2 hours)
it is more likely that WW issuance will be closer to 01Z. All severe
modes including large hail, tornadoes and damaging wind will be
possible. Another mesoscale discussion will likely be needed closer
to WW issuance time.

DISCUSSION...As of late afternoon a quasi-stationary/warm front
extends across northern AR through central OK and westward into the
TX panhandle where it intersects a dryline. The warm sector
continues to moisten with mid-upper 60s F dewpoints as far north as
northeast TX and southern AR. Within the moistening warm sector,
scattered convection has been increasing in coverage from LA through
southern AR, but lack of lightning suggests this activity remains
shallow, and indeed special 18Z RAOBs indicate presence of modest
capping inversions between 800 and 500 mb. Objective analysis shows
the atmosphere has become moderately unstable with MLCAPE from
1000-1500 J/kg, and further destabilization is likely as zone of
ascent and cooler temperatures aloft spread eastward above the
western half of the moistening boundary layer. WV imagery and RAP
analysis shows a potent negative-tilt shortwave trough moving
eastward into the southern High Plains. The zone of deeper ascent
associated with this feature (manifested by plume of expanding
cirrus) is currently moving through northwest TX into western and
central OK. By early-mid evening this zone of ascent will begin to
interact with corridor of greater instability from northeast TX into
eastern OK and eventually AR and LA, resulting in removal of any
remaining inversions and deepening updrafts. Moreover, wind profiles
will strengthen with the low-level jet increasing to 50+ kt and 0-1
km hodographs increasing significantly by mid evening. These
processes suggest storms will undergo a substantial increase in
organization and intensification, especially after 01Z with
supercells capable of large hail, damaging wind and tornadoes
becoming likely.

..Dial/Hart.. 11/30/2018

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

ATTN...WFO...JAN...LZK...SHV...TSA...FWD...

LAT...LON 35969489 35949295 35729160 34759126 32579217 31779377
32499527 34509559 35969489



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