Graphic for MPD #0753

MESOSCALE PRECIPITATION DISCUSSION 0753...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
429 PM EDT MON AUG 28 2017

CORRECTED FOR FLASH FLOOD CATEGORY

AREAS AFFECTED...FAR SOUTHEAST TX...CENTRAL AND SOUTHERN LA INTO
SOUTHERN MS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 282015Z - 290115Z

SUMMARY...CONVECTION IN THE WARM SECTOR OF TROPICAL STORM HARVEY
IS EXPECTED TO PRODUCE FLASH FLOODING...ESPECIALLY OVER PORTIONS
OF LA INTO COASTAL MS INTO THE EVENING HOURS.

DISCUSSION...THE GOES-16 CLEAN IR LOOP SHOWED COOLING TOPS WITH
CONVECTION OVER SOUTHERN LA AND SOUTHERNMOST MS THIS AFTERNOON.
THE CONVECTION WAS DEVELOPING/MOVING THROUGH AN AXIS OF 1500-2000
J/KG MLCAPE...ON THE NOSE OF A 20 TO 30 KNOT LOW LEVEL SOUTHERLY
JET. THE DEEPEST MOISTURE (WITH PRECIPITABLE WATER VALUES NEAR
2.50 INCHES) WAS LOCATED THIS AREA. AS A RESULT...HOURLY RAINFALL
RATES WITH THE CONVECTION WAS TOPPING OUT NEAR 2.00 INCHES OVER
PORTIONS THE CENTRAL LA COAST.

THE LOW LEVEL INFLOW IS EXPECTED TO REMAIN INTACT INTO THE
EVENING...CONTINUING TO FEED INSTABILITY AND MOISTURE ACROSS
SOUTHERN LA INTO SOUTHWEST MS. THE RESULTING CONVECTIVE BANDS
MOVING NORTH FROM THE GULF OF MEXICO COULD PRODUCE LOCAL 3.00 TO
5.00 INCHES OF RAINFALL IN A RELATIVELY SHORT PERIOD OF TIME
(GENERALLY LESS THAN TWO HOURS). THIS MUCH RAIN... ESPECIALLY OVER
AREAS WITH LOWER FLASH FLOOD GUIDANCE VALUES DUE TO EARLIER HEAVY
RAINFALL...IS EXPECTED TO RESULT IN NEW/ADDITIONAL FLASH FLOODING
INTO THE EVENING.

FURTHER NORTH...THE LOW LEVEL INFLOW OVER A FRONTAL BOUNDARY
STRETCHING FROM THE UPPER TX COAST ACROSS COASTAL LA INTO NORTHERN
FL IS SENDING MOISTURE AND INSTABILITY UP THE ISENTROPIC SURFACE
ACROSS CENTRAL LA... WHERE THE CONVECTION BECOMES ELEVATED AND
MORE DIFFUSE. HOURLY RAINFALL RATES HERE ARE MORE
MODEST...GENERALLY CLOSER TO AN INCH OR SO. HOWEVER...REGIONAL
RADARS INDICATED THAT THESE LOCATIONS MAY HAVE ALREADY RECEIVED AS
MUCH AS 7.00 INCHES OF RAINFALL...SO EVEN MODERATE RAINFALL RAINS
COULD RESULT IN ADDITIONAL FLASH FLOODING.

HAYES

ATTN...WFO...HGX...JAN...LCH...LIX...MOB...SHV...

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

LAT...LON   32069161 30688874 30628865 30408846 30148842
            29818859 29498889 29058918 28978954 28969000
            29029071 29529228 29639346 29519397 29439445
            29779480 30419423 31159368


Last Updated: 429 PM EDT MON AUG 28 2017