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ACUS11 KWNS 201032
SPC MCD 201032

Mesoscale Discussion 0197
NWS Storm Prediction Center Norman OK
0432 AM CST Mon Feb 20 2017

Areas affected...Deep South Texas

Concerning...Severe potential...Watch unlikely

Valid 201032Z - 201330Z

Probability of Watch Issuance...20 percent

SUMMARY...Locally strong wind gusts and/or a brief tornado will be
possible through 12-14Z across Deep South Texas to portions of the
middle Texas coast.  Given expected sparse coverage of the overall
severe-weather threat, a watch is not anticipated into the early
morning as storms move toward the Texas Gulf coast.

DISCUSSION...Another forward-propagating MCS has developed across
Deep South Texas early this morning (since about 08Z per
radar/satellite trends), with the band of storms extending from Live
Oak and Jim Wells Counties to the lower Rio Grande River/
international border in Hidalgo County and into northern Tamaulipas
Mexico.  Surface analysis showed a convective outflow boundary
extending northeast from northwest Kenedy County to just inland of
the middle Texas coast, and then north-northeast to the ongoing MCS
moving through east Texas.  The environment south of this boundary
from the middle Texas coast to Deep South Texas remains moderately
unstable with strong effective bulk shear vectors oriented parallel
to the surface boundary and the north-south oriented band of storms
in Deep South Texas.

These storms appear to be located along the leading edge of forcing
for ascent and height falls attendant to the large-scale trough
moving east from the Texas Big Bend region and northern Mexico.
This forcing has weakened the cap across Deep South Texas allowing
for the storms to form within the moderate instability.  Given deep
meridional flow across the discussion area, propagation of the band
of storms will remain slow toward the east, while some portions of
the band/QLCS track to the northeast at 25-30 kt.  Locally strong
wind gusts will be possible, while effective SRH exceeding 200 m2/s2
suggest a tornado cannot be ruled out (especially with mesovortices
within the QLCS).

..Peters/Edwards.. 02/20/2017

...Please see for graphic product...


LAT...LON   27779771 28939625 28509582 28049661 27599703 26999714
            25949696 25789738 25979818 26519794 27099768 27389768
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