MESOSCALE PRECIPITATION DISCUSSION 0285
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 AM EDT THU OCT 31 2013
 
AREAS AFFECTED...EASTERN TX/SOUTHWESTERN AR/NORTHWESTERN LA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 310601Z - 311116Z
 
SUMMARY...FLASH FLOODING IS CURRENTLY ONGOING ALONG A LINE OF
TRAINING CONVECTION EXTENDING FROM SOUTH OF SAN ANTONIO TX
NORTHEASTWARD TO JUST OUTSIDE TYLER TX. NUMEROUS WATER RESCUES
HAVE ALREADY BEEN REPORTED WITH HEAVY RAINFALL CONTINUING TO
ENHANCE THE RISK FOR ADDITIONAL FLASH FLOODING.

DISCUSSION...A SOUTHWEST TO NORTHEAST LINE OF CONVECTION HAS
PERSISTED IN A QUASI-STATIONARY STATE SINCE APPROXIMATELY 02Z.
THERE HAS ALREADY BEEN A CONFIRMED REPORT OF 4.85 INCHES OF
RAINFALL IN ONLY A 75 MINUTE PERIOD WHICH WOULD SUGGEST NEAR 4
INCH RAIN RATES PER HOUR. ADDITIONAL SUPPORT FROM THE MESONET
OBSERVATIONS INDICATED 2 TO 3 INCH RAINFALL AMOUNTS IN AN HOUR
WITHIN THE AFFECTED REGION. AS EXPECTED...THE FFG VALUES HAVE COME
CRASHING DOWN WHICH WILL ALLOW VERY LITTLE PRECIPITATION TO EXCEED
GUIDANCE.

THE PATTERN HAS NOT CHANGED A WHOLE LOT SINCE THE PREVIOUS
ISSUANCE. AHEAD OF A SHORTWAVE ADVANCING INTO NORTHEASTERN NEW
MEXICO...ANOMALOUS MOISTURE TRANSPORT IS BRINGING ABOVE 2 INCH
PWATS INTO SOUTH AND EAST TX. THE 05Z RAP FORECAST SOUNDINGS
DEPICT DEEP-LAYERED UNIDIRECTIONAL SOUTHWESTERLY FLOW WILL PERSIST
OVER THE REGION ALTHOUGH WINDS DO VEER OVER TO WESTERLY BY ABOUT
10Z. IN THE MEANTIME...THERE IS LITTLE REASON TO EXPECT THE
CHARACTER OF THE CONVECTION TO CHANGE DURING THE NEXT FEW HOURS.
SUFFICIENT INSTABILITY SOUTH OF THE PERSISTENT CONVECTION IS NOTED
AS THE 05Z RAP SHOWS 1000-1500 J/KG OF MLCAPE IS PRESENT. THIS IS
FURTHER SUPPORTED BY THE INFRARED SATELLITE SHOWING RENEWED
CONVECTION ALONG THE SOUTHWESTERN FLANK WITH -80C TOPS ACCOMPANIED
BY A FEW OVERSHOOTING TOPS.

FLASH FLOODING WILL REMAIN LIKELY THE NEXT SEVERAL HOURS ALTHOUGH
THE SHIELD OF PRECIPITATION SHOULD EVENTUALLY BECOME MORE FORWARD
PROPAGATING AS THE UPSTREAM SHORTWAVE APPROACHES FROM THE WEST.


RUBIN-OSTER

ATTN...WFO...SHV...HGX...FWD...EWX...

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

LAT...LON   29279921 30129899 31329759 32019645 33149531 33729431
            33509349 32639344 31869439 31269529 30579629 29089820
            29279921