MESOSCALE PRECIPITATION DISCUSSION 0738
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
645 PM EDT SAT AUG 26 2017

AREAS AFFECTED...SOUTHEAST TX AND SOUTHWEST LA

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

VALID 262245Z - 270145Z

SUMMARY...BANDING ASSOCIATED WITH TROPICAL STORM HARVEY WILL
CONTINUE TO AFFECT PORTIONS OF SOUTHEAST TX INTO SOUTHWEST LA
THROUGH THE EVENING HOURS. SIGNIFICANT FLASH FLOODING IS EXPECTED
WHERE THE BANDING PERSISTS.

DISCUSSION...THE GOES-16 CLEAN IR LOOP HAS SHOWN THAT THE TOPS ON
THE BANDING FEATURES EAST OF TROPICAL STORM HARVEY HAVE WARMED
OVER THE PAST FEW HOURS. THIS HAS BEEN REFLECTED IN THE REGIONAL
RADAR IMAGERY... AS THE BANDING OVER THE UPPER TX COAST AND
PORTIONS OF SOUTHWEST LA ARE NOT QUITE AS ROBUST AS EARLIER IN THE
AFTERNOON.

PRECIPITABLE WATER VALUES REMAIN BETWEEN 2.50 AND 2.75 INCHES (PER
THE MOST RECENT RAP ANALYSIS) IN THE CIRCULATION AROUND
HARVEY...AND THE DEEP TROPICAL MOISTURE CONTINUES TO FEED BANDING
ACROSS THE UPPER TX COAST. THE LOW LEVEL CONVERGENT FLOW IS
FOCUSING THE DEEP MOISTURE INTO CONVECTIVE BANDS EAST OF THE
CENTER OF HARVEY... RESULTING IN AN ASYMMETRIC RAINFALL
DISTRIBUTION.  THE KHGX RADAR SHOWED HOURLY RAINFALL RATES NEAR
2.50 INCHES IN BANDING JUST WEST OF KIAH...AND THE KLCH RADAR
SHOWED HOURLY RAINFALL RATES CLOSER TO 2.00 INCHES APPROACHING THE
TX/LA BORDER.

THERE IS A STRONG HIGH RESOLUTION MODEL SIGNAL FOR LOCAL 3.0 TO
5.00+ INCH RAINFALL AMOUNTS THROUGH 0130Z OVER PORTIONS OR THE
MIDDLE AND UPPER TX COAST (LED BY THE MOST RECENT HRRR...WHICH
SHOWED 6.00+ INCH AMOUNTS IN BANDING BOTH WEST AND EAST OF THE
HOUSTON METRO AREA). THE HIGHEST RAINFALL AMOUNTS ARE EXPECTED
WHERE THE BANDING PERSISTS...AND WILL PRODUCE SIGNIFICANT FLASH
FLOODING INTO THE EVENING HOURS.

LESSER AMOUNTS ARE POSSIBLE ACROSS PORTIONS OF NEARBY SOUTHWEST
LA...WHERE THE HIGH RESOLUTION MODEL SIGNAL IS NOT QUITE AS STRONG
FOR SIGNIFICANT FLASH FLOODING. HOWEVER...PORTIONS OF SOUTHWEST LA
HAVE ALREADY RECEIVED THEIR AVERAGE YEARLY RAINFALL...AND REMAINS
SENSITIVE TO ADDITIONAL HEAVY RAINFALL.

HAYES

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

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

LAT...LON   31589484 31019318 30469230 29999208 29849309
            29579425 29009516 28489576 28459655 28899775
            29219785 30029745 30959641