MESOSCALE PRECIPITATION DISCUSSION 0265
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1211 PM EDT MON SEP 30 2013
 
AREAS AFFECTED...EXTREME EASTERN TX...WESTERN LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 301545Z - 302045Z
 
SUMMARY...VERY SLOW-MOVING CLUSTER OF HVY SHWRS/TSTMS TO PERSIST
OVER THE NEXT SEVERAL HOURS....WITH ADDITIONAL FLASH FLOOD
CONCERNS EXPECTED AT LEAST LOCALLY. 

DISCUSSION...SAT IMAGERY SHOWS CLUSTERS OF MODERATELY COLD CLOUD
TOP CONVECTION OVER EXTREME EASTERN TX AND INTO SOUTHWESTERN LA
WHERE IT IS MORE DISORGANIZED. THE CONVECTION IS IN ASSOC WITH A
WEAK AREA OF SFC LOW PRESSURE AND IS DYNAMICALLY BEING AIDED BY A
WEAK UPPER VORTICITY MAXIMA. THE LATEST WV IMAGERY OVER THE REGION
DOES SUGGEST SOME WEAK BACKING OF THE MID LVL FLOW OVER THE
REGION...AND SOME RELATIVELY DIV FLOW ALOFT. THE CONVECTION HAS
BEEN QUITE PERSISTENT DESPITE ITS LOCALIZED NATURE...HOWEVER THE
LATEST VIS SHOWS AGITATED CU/TCU FIELD EMBEDDED WITHIN LOW/MID LVL
SWLY FLOW ALONG THE UPR TX COAST. 

THE MAIN CONCERN IS FOR ADDITIONAL BACK-BUILDING AND MERGING OF
CONVECTIVE CELLS INVOF TX/LA BORDER AREA AND ADJACENT
COUNTIES...ESP SEWD INTO SWRN LA ALONG A LOW LVL WEAK CONVERGENCE
ZONE THE NEXT FEW HOURS. THE THERMODYNAMIC ENVIRONMENT SUGGESTS
ADDITIONAL CONVECTIVE DEVELOPMENT IS LIKELY...ESP WITH THE
MAINTENANCE OF MOIST/UNSTABLE LOW LVL FLOW IN OFF THE GULF OF
MEXICO...ALBEIT WEAK....BUT ALSO WITH AN INTRUSION OF COLD/DRY MID
LVL AIR AS SUGGESTED BY WV IMAGERY. GIVEN THE SLOW MOVEMENT OF THE
CONVECTIVE CELLS/CLUSTERS...AND PWATS AS PER LATEST
GOES-SOUNDER/GPS DATA OF 1.9 TO 2.2 INCHES...EXPECT ADDITIONAL HVY
RAINFALL RATES OF UP TO 2 INCHES/HR AND POSSIBLY HIGHER. ALREADY
ON A VERY LOCALIZED LVL THERE HAVE BEEN VERY HVY RAINFALL AMTS.
ADDITIONAL HVY RAINS WILL BE POSSIBLE OVER ALREADY IMPACTED AREAS
AROUND NEWTON/JASPER TX...BUT WITH SOME CONCERN FOR A LARGER SCALE
IMPACT OVER THE NEXT FEW HOURS INVOLVING ADJACENT COUNTIES. WILL
CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...LCH...SHV...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   30469253 30019221 29659250 29749301 29849366 29769416
            30169448 31049435 31509405 31619346 31319300 30829275
            30469253