MESOSCALE PRECIPITATION DISCUSSION 0079
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
927 PM EDT MON MAY 11 2015
 
AREAS AFFECTED......SOUTH TX... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 120124Z - 120500Z
 
SUMMARY...STRONG INSTABILITY AND DEEP MOISTURE ARE COMBINING TO
PRODUCE HIGH RAINFALL RATE CONVECTION...RESULTING IN THE POTENTIAL
FOR FLASH FLOODING.

DISCUSSION...CONVECTION IS BEGINNING TO COALESCE ACROSS SOUTH TX
EARLY THIS EVENING...AS INSTABILITY (WITH MLCAPE VALUES GREATER
THAN 2000 J/KG) AND A PRECIPITABLE WATER AXIS (WITH VALUES MORE
THAN 2.00 INCHES) COINCIDE. FOR THE MOST PART...THE ACTIVITY HAS
BEEN SCATTERED...AND WITH RELATIVELY WEAK MID LEVEL FLOW...IT HAS
BEEN SLOW MOVING. HOWEVER...A BETTER COMPLEX IS FORMING OVER
BROOKS COUNTY (EVEN THOUGH CLOUD TOPS HAVE WARMEST RECENTLY). KCRP
RADAR HAS INDICATED IN EXCESS OF 2.50 INCHES AN HOUR WITH THE
NEWEST ACTIVITY.

IN THE NEAR TERM...HIGH RESOLUTION GUIDANCE (SUCH AS THE LATEST
HRRR/RAP/WRF-ARW) SUGGEST THAT MOVEMENT OF THE DEVELOPING
CONVECTION WILL BE SLOW AND TO THE NORTH... RESULTING IN RAINFALL
RATES IN EXCESS OF 2 INCHES AN HOUR. HOWEVER...THERE IS SOME
SPREAD CONCERNING WHERE THE HEAVIEST QPF RAINFALL AMOUNTS WILL
BE...PENDING THE ARRIVAL OF BETTER STEERING FLOW DURING THE
OVERNIGHT. LOCAL RAINFALL AMOUNTS OF 5 INCHES ARE
POSSIBLE...ESPECIALLY WHERE CELL MERGERS OCCUR. 

WHILE ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE
RELATIVELY HIGH (GREATER THAN 3.00 INCHES IN MOST PLACES IN SOUTH
TX)...THE COMBINATION OF HIGH RAINFALL RATES AND SLOW CELL
MOVEMENT MAKES FLASH FLOODING LIKELY...ESPECIALLY WHERE CELL
MERGERS OCCUR.

HAYES

ATTN...WFO...BRO...CRP...EWX...

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

LAT...LON   29600003 29149866 27899788 26879755 26249777 
            26279860 26269855 26759951 28170073 29470108