MESOSCALE PRECIPITATION DISCUSSION 0238
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
854 PM EDT WED JUN 17 2015
 
AREAS AFFECTED...SOUTHERN TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 180053Z - 180553Z
 
SUMMARY...SLOW MOVING CONVECTION ALONG OLDER OUTER BAND OF
TROPICAL DEPRESSION BILL CAPABLE OF 3"/HR RATES WITH LOCALIZED
EXTREME TOTALS FOR HIGH IMPACT FLASH FLOODING OVER THE NEXT FEW
HOURS. 

DISCUSSION...EXTREME TOTALS ARE THE NORM WITH HIGHLY EFFICIENT
CELLS WITHIN VERY SLOW MOVING FLOW. 00Z CRP SOUNDING IS VERY
IMPRESSIVE WITH FULLY SATURATED PROFILE WITH PW OVER 2.5" AS WELL
AS AVAILABLE CAPE IN EXCESS OF 3500 J/KG.  STRONG SOUTHERLY FLOW
IS MAINTAINING A WSW TO ENE BOUNDARY FROM ZAPATA TO SAN PATRICIO
COUNTIES.  VISIBLE AND IR IMAGERY SHOW EXPLOSIVE CONVECTION TO
-80C ACROSS THIS BOUNDARY...GIVEN THE AVAILABLE MOISTURE AND
INSTABILITIES RAIN RATES IN THE 3"/HR RANGE ARE THE NORM NOT THE
EXCEPTION.  WITH THE EXITING OF BILL TO THE NORTH...FLOW HAS
SLACKED SIGNIFICANTLY IN THE CLOUD BEARING LAYER FOR VERY WEAK
CELL MOTIONS FOR NEARLY STATIONARY FOR SLOWLY OR MERGING CELLS. 
THIS HAS LEAD TO SOME EXTREME LOCALIZED TOTALS AND HIGH IMPACT
FLASH FLOODING. 

CELLS ACROSS NORTHERN MEXICO CONTINUE TO EXPAND AND GROW NORTHWARD
ALONG A SIMILAR SEA BREEZE BUT IS ORIENTED MORE NORTH/SOUTH
INTERSECTING WITH WSW-ENE BOUNDARY NEAR ZAPATA
COUNTY...EXPECTATION IS FOR MERGER/EXPANSION NORTHWARD INTO SOUTH
TEXAS LEADING TO INCREASED LOCALIZED TOTALS AS WELL.  CONTINUED
INTERACTION AND MERGERS WILL BE LIKELY THROUGHOUT THE BRO CWA AS
THESE TWO COMPLEXES EVOLVE AND EXHAUST THE VERY HIGH AVAILABLE
INSTABILITIES OVER THE NEXT 3-5 HOURS. 

GALLINA

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

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

LAT...LON   28609690 28279645 27099731 26059705 25899725 
            26379894 27239946 28169940