MESO: Mesoscale Discussion 0583

ACUS11 KWNS 301448
SWOMCD
SPC MCD 301447
LAZ000-301645-

MESOSCALE DISCUSSION 0583
NWS STORM PREDICTION CENTER NORMAN OK
0947 AM CDT TUE APR 30 2013

AREAS AFFECTED...FAR SOUTH-CENTRAL/SOUTHEAST LA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 301447Z - 301645Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A LOCALIZED DAMAGING WIND/PERHAPS BRIEF TORNADO RISK MAY
DEVELOP INTO COASTAL PORTIONS OF SOUTH-CENTRAL/SOUTHEAST LA THROUGH
LATE MORNING/EARLY AFTERNOON. A WATCH IS NOT CURRENTLY ANTICIPATED.

DISCUSSION...AN EXTENSIVE MCS IS ONGOING OVER THE WESTERN GULF OF
MEXICO THIS MORNING AHEAD OF A WEAK/SLOW-MOVING UPPER LOW MOVING
EASTWARD OVER THE MIDDLE TX COAST/FAR NORTHWEST GULF. THE NORTHERN
PORTION OF THIS MCS...INCLUDING AN EMBEDDED/TRAILING NORTH-END
VORTEX...WILL LIKELY AT LEAST GRAZE COASTAL PORTIONS OF
SOUTH-CENTRAL/SOUTHEAST LA AS IT MOVES NORTHEASTWARD THROUGH LATE
MORNING/EARLY AFTERNOON...ESPECIALLY THROUGH THE 1530Z-1800Z TIME
FRAME. WHILE THICK CLOUD COVER PREVAILS AHEAD OF THE MCS...THE
BOUNDARY LAYER CONTINUES TO STEADILY WARM THIS MORNING ACROSS
SOUTHERN LA IN CONJUNCTION WITH NEAR 70F SURFACE DEWPOINTS.
MODIFICATIONS TO THE 12Z OBSERVED SOUNDING FROM SLIDELL LA SUPPORT
AS MUCH AS 1500 J/KG OF MLCAPE. EVEN WHILE THE WESTERLIES ALOFT ARE
RELATIVELY WEAK INLAND...FACTORS SUCH AS MODERATE
INSTABILITY...STEEPENING LAPSE RATES...AND LOW LEVEL EASTERLY
WINDS...WILL LIKELY CONTRIBUTE TO A CONTINUED NORTHEASTWARD
MOTION/PROPAGATION INTO SOUTH-CENTRAL/SOUTHEAST LA OVER THE NEXT FEW
HOURS. ALTHOUGH THE FORWARD MOTION /30 KT/ IS NOT PARTICULARLY
FAST...SOME ADDITIONAL/GRADUAL ACCELERATION OF THE CONVECTIVE LINE
COULD OCCUR...AND REGARDLESS...LOCALIZED DAMAGING WINDS/PERHAPS EVEN
A BRIEF TORNADO MAY BE POSSIBLE.

..GUYER/HART.. 04/30/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LIX...LCH...

LAT...LON 29299175 29719115 30168978 30048910 29428871 28718914
28488995 28519057 29009074 29139148 29299175

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