MESOSCALE PRECIPITATION DISCUSSION 0728
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT FRI AUG 25 2017

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

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

VALID 251845Z - 260000Z

SUMMARY...OUTER BANDS FROM HARVEY WILL CONTINUE TO CROSS PORTIONS
OF SOUTHWEST LA INTO THE UPPER TX COAST. THE ADDITIONAL RAINFALL
COULD POSE A CONTINUED FLASH FLOOD THREAT THROUGH THE AFTERNOON
HOURS.

DISCUSSION...THE GOES-16 CLEAN IR LOOP SHOWED OUTER BANDS FROM
HURRICANE HARVEY CONTINUING TO MOVE NORTH TOWARD THE SOUTHWEST LA
COAST AND THE UPPER COAST OF TX. TOPS HAVE BEEN ALTERNATELY
WARMING AND COOLING...WITH THE COLDEST TOPS APPROACHING THE
SOUTHWEST AND CENTRAL LA COAST. THE KLCH RADAR SHOWED HOURLY
RAINFALL RATES BETWEEN 1.50 AND 2.00 INCHES WITH THE INITIAL OUTER
BANDS...AND GIVEN THE  TROPICAL AIRMASS IN PLACE (WITH THE MOST
RECENT RAP SHOWING PRECIPITABLE WATER VALUES BETWEEN 2.25 AND 2.50
INCHES)... THESE HOURLY RAINFALL RATES ARE POSSIBLE ALONG THE LATE
AFTERNOON HOURS.

THE BEST INSTABILITY APPEARS TO LIE NEAR THE COAST (AND CLOSE TO
THE FRONTAL BOUNDARY IN PLACE)...AND THE LOW LEVEL CONVERGENT FLOW
IS FOCUSING THE INSTABILITY AND DEEP MOISTURE ALONG THE COAST.
MOST OF THE HIGH RESOLUTION MODELS SUGGEST THAT THE UPPER TX COAST
WILL SEE THE HIGHEST RAINFALL AMOUNTS ASSOCIATED WITH THE OUTER
BANDS. THE MOST RECENT HRRR SHOWED LOCAL 5.00+ INCH AMOUNTS OVER
THE UPPER TX COAST...AND GIVEN WHAT HAS ALREADY OCCURRED...THESE
AMOUNTS SEEM PLAUSIBLE WHERE BANDS PERSIST OR TRAIN.

THE ADDITIONAL RAINFALL COULD BE A FLASH FLOOD ISSUE IN PLACES
LIKE PORT O'CONNOR... WHERE DAM ISSUES REMAIN. IN ADDITION...
PORTIONS OF SOUTHWEST LA HAVE RECEIVED THEIR ANNUAL RAINFALL...AND
MAY ALSO BE SENSITIVE TO THE ADDITIONAL HEAVY RAINFALL.

HAYES

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

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

LAT...LON   30659324 30649251 30349202 29909185 29559236
            29599408 29249475 29019508 29639558 30089512
            30539414