MESOSCALE PRECIPITATION DISCUSSION 0184
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
444 PM EDT WED MAY 03 2017

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

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

VALID 032045Z - 040130Z

SUMMARY...FLASH FLOODING IS EXPECTED TO CONTINUE AS CONVECTION
TRACKS ACROSS AREAS WITH SATURATED SOILS INTO THE EARLY EVENING
HOURS.

DISCUSSION...THE REGIONAL RADAR MOSAIC CONTINUED TO SHOW
CONVECTION TO FORM OVER FAR EASTERN TX IN AN AXIS OF 1500 TO 3000
J/KG OF MLCAPE. THE LATEST EXPERIMENTAL GOES 16 IR IMAGERY SHOWED
AN EXPANDING AREA OF COOLING TOPS WITH THE CONVECTION...AS IT
TRACKS INTO PORTIONS OF WEST CENTRAL LA. THE CONVECTION IS FORMING
IN AN AXIS OF 1.75 INCH PRECIPITABLE WATER AIR (PER THE LATEST
BLENDED TPW PRODUCT AND THE LATEST RAP ANALYSIS.

THE KPOE RADAR SHOWED HOURLY RAINFALL RATES NEAR 2.00 INCHES WITH
THIS ACTIVITY...BUT RECENT SPOTTER REPORTS SUGGEST THAT THESE
VALUES COULD BE HAIL CONTAMINATED. FURTHER SOUTH...CLOSER TO THE
LA COAST...EARLIER CONVECTION HAS RESULTED IN A MORE STABLE
ENVIRONMENT. THIS IS REFLECTED IN THE DOWNTICK OF CONVECTIVE
ACROSS FAR SOUTHERN LA.

THE DROP OFF IN THE CONVECTION NEAR THE COAST IS IMPORTANT...AS
THERE IS A SPLIT IN THE HIGH RESOLUTION GUIDANCE WITH RESPECT TO
THE PLACEMENT OF THE AXIS OF MAXIMUM QPF. THE 12Z WRF-ARW IS
PLACING HIGHEST QPF MAXIMUM (BETWEEN 4.00 AND 6.00 INCHES) FURTHER
SOUTH...STRETCHING FROM FAR SOUTHEAST TX TO JUST NORTH OF THE
SOUTHERN LA COAST. BASED ON THE CURRENT RADAR TRENDS...THIS MAY BE
TOO FAR SOUTH.

OTHER HIGH RESOLUTION GUIDANCE (SUCH AS THE LATEST HRRR) IS
FURTHER NORTH...CLOSE TO WHERE THE CONVECTION IS FLARING IN THE
BEST INSTABILITY GRADIENT. THERE IS STRONG HIGH RESOLUTION MODEL
SIGNAL FOR LOCAL 3.00 TO 5.00 INCH QPF AMOUNT) WHERE THE
CONVECTION TRAINS.

BASED ON SPOTTER REPORTS AND THE LATEST HRRR SOIL SATURATION
PRODUCT INDICATED SATURATED SOILS OVER MUCH OF CENTRAL AND
SOUTHERN LA...SO THE ADDITIONAL RAINFALL IS EXPECTED TO EXACERBATE
ONGOING FLOODING... AS WELL AS PRODUCE NEW AREAS OF FLOODING INTO
SOUTH CENTRAL LA.

THE POTENTIAL FOR ADDITIONAL FLOODING EXISTS BEYOND THE VALID TIME
OF THIS MPD... AND THAT POTENTIAL WILL BE ADDRESSED IN SUBSEQUENT
MESSAGES.

HAYES

ATTN...WFO...JAN...LCH...LIX...SHV...

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

LAT...LON   31589326 31529127 31109045 30309109 30099365
            30839434 31309426