SPC MD 605

MD 0605 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF COASTAL SOUTHEAST TX...SOUTHERN/EASTERN LA...AND FAR SOUTHWEST MS

Mesoscale Discussion 0605
NWS Storm Prediction Center Norman OK
0114 AM CDT Sun Apr 30 2017

Areas affected...Portions of coastal southeast TX...southern/eastern
LA...and far southwest MS

Concerning...Severe potential...Watch possible 

Valid 300614Z - 300745Z

Probability of Watch Issuance...60 percent

SUMMARY...Isolated strong to damaging winds and a tornado or two
will be possible with storms increasing in coverage along and ahead
of a cold front. Watch issuance is possible.

DISCUSSION...As of 06Z, a cold front extends southward across east
TX to the vicinity of Houston. Convection has recently increased in
coverage and intensity along and ahead of the front in southeast TX
and southwestern LA. 00Z sounding from Lake Charles LA showed a very
moist low-level airmass is in place across the LA/TX coast, with
dewpoints in the mid 70s and a mean mixing ratio of 17.5 g/kg. Steep
lapse rates around 7.5 C/km in the 700-500 mb layer along with the
plentiful low-level moisture are contributing to strong instability
across the discussion area, with latest RAP Mesoanalysis suggesting
MLCAPE generally ranges from 2000-3000 J/kg. Effective bulk shear of
45-50 kt will conditionally support supercells ahead of the
eastward-moving front, although convection may become organized into
clusters with time due to strong low-level warm air advection
associated with a 40-50 kt southerly low-level jet. Isolated strong
to locally damaging winds with convection along the cold front
should be the main severe threat through the overnight hours,
although a tornado or two may occur with convection both ahead of
and within the line given modestly veering low-level winds and
effective SRH around 200-350 m2/s2. Some large hail may also be
possible, mainly with any supercells ahead of the line.

..Gleason/Guyer.. 04/30/2017

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

ATTN...WFO...JAN...LIX...LCH...SHV...HGX...

LAT...LON   29549270 29709329 29619385 29279476 29669525 30549484
            30979462 31049413 31229321 31479268 31899223 32539205
            32689146 32519085 31749089 30879115 30139144 29399171
            29439234 29549270 

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