MESOSCALE PRECIPITATION DISCUSSION 0733
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
939 PM EDT FRI AUG 25 2017

AREAS AFFECTED...UPPER TX COAST AND NEARBY SOUTHWEST LA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 260135Z - 260635Z

SUMMARY...OUTER BANDS FROM HURRICANE HARVEY WILL CONTINUE TO CROSS
THE UPPER TX COAST AND NEARBY SOUTHWEST LA INTO THE EARLY MORNING
HOURS.

DISCUSSION...THE GOES-16 CLEAN IR LOOP SHOWED BURSTS OF DEEP
CONVECTION IN THE OUTER BANDS OF HURRICANE HARVEY SOUTH OF THE
CENTRAL LA COAST...AS WELL OVER THE UPPER TX COAST SOUTH OF
HOUSTON...WHERE CLOUD TOPS TEMPERATURES WERE NEAR -75 DEGREE
CELSIUS. 

THE HGX RADAR SHOWED HOURLY RAINFALL RATES NEAR 2.00 INCHES WITH
THE DEEP CONVECTION JUST SOUTH OF THE HOUSTON METRO AREA. AS THE
BANDING HAS APPROACHED THE COAST... INSTABILITY DECREASED NEAR A
FRONTAL
BOUNDARY EXTENDING FROM THE MIDDLE TX COAST THROUGH SOUTHERN MS.
THE BEST INSTABILITY LIES SOUTH OF THE FRONT...AND AS THE
CONVECTION APPROACHES THE COAST... ISENTROPIC LIFT OVER THE FRONT
HAS BEEN SPREADING OUT THE ELEVATED INSTABILITY... RESULTING IN A
WEAKENING TREND FOR MOST OF THE OUTER BANDS.

THE BANDING FEATURES ARE EXPECTED TO CONTINUE COMING ASHORE OVER
THE UPPER TX COAST AND NEARBY SOUTHWEST LA THROUGH THE EARLY
MORNING HOURS. THE CONVECTION IS EXPECTED WEAKEN A BIT AS IT
REACHES THE
COAST...BUT HOURLY RAINFALL RATES OF 2.00 INCHES COULD RESULT IN
LOCAL 2.50 TO 5.00 INCHES OF QPF...ESPECIALLY WHERE THE BANDING
ALLOWS SHORT TERM TRAINING IN THE VICINITY OF HOUSTON.

WHILE IS POSSIBLE THAT THE HRRR IS OVERESTIMATING THE AVAILABLE
INSTABILITY...THE CONTINUED HEAVY RAINFALL WITH THE BANDING
FEATURES WILL EXTEND THE FLASH FLOOD THREAT INTO THE EARLY MORNING
HOURS.

HAYES

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

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

LAT...LON   30639306 30569204 30409152 30039137 29619187
            29589305 29639382 29339451 29169477 28999568
            29499573 29919525 29989503 30519393