Graphic for MPD #0654

MESOSCALE PRECIPITATION DISCUSSION 0654...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
224 PM EDT TUE AUG 08 2017

CORRECTED FOR AREAS AFFECTED IN HEADER AND SUMMARY SECTION

AREAS AFFECTED...SERN TX INTO WRN LA

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

VALID 081820Z - 090020Z

SUMMARY...SLOW MOVING CONVECTION WITH RAINFALL RATES CAPABLE OF 3
IN/HR IS EXPECTED TO DEVELOP OVER PORTIONS OF SERN TX INTO WRN LA
THIS AFTERNOON. GIVEN WET ANTECEDENT CONDITIONS...FLASH FLOODING
WILL BE POSSIBLE.

DISCUSSION...A SLOW MOVING MCV WAS NOTED ALONG THE
HARRIS/MONTGOMERY COUNTY BORDER AT 18Z VIA EXPERIMENTAL GOES 16
VISIBLE IMAGERY. OVERCAST SKIES DIRECTLY BENEATH THE CIRCULATION
HAVE BEEN LIMITING SOLAR INSOLATION AND INSTABILITY BUT SOME
BREAKS IN CLOUD COVER TO THE EAST TOWARD THE SABINE RIVER HAVE
HELPED MLCAPE TO REACH 500-1500 J/KG ACCORDING TO 17Z DATA FROM
THE SPC MESOANALYSIS PAGE. GIVEN ABUNDANT MOISTURE...GPS
PRECIPITABLE WATER VALUES OF 2.2 TO 2.4 INCHES...AND WET BULB ZERO
HEIGHTS OF 15-16 KFT...PER 12Z LCH SOUNDING AND RAP ANALYSIS
SOUNDINGS OVER SERN TX...THE ENVIRONMENT IS POISED TO PRODUCE VERY
HEAVY RAINFALL DOMINATED BY WARM RAIN PROCESSES.

850 MB WINDS ON THE SOUTHEAST SIDE OF THE MCV HAVE WEAKENED FROM
EARLIER THIS MORNING TO ABOUT 20 KT PER RECENT VAD WIND DATA FROM
KIAH AND RAP ANALYSES...RESULTING IN WEAKER AVAILABLE INFLOW INTO
CONVECTION...BUT GIVEN TRENDS IN VISIBLE SATELLITE IMAGERY AND AN
UNCAPPED ATMOSPHERE...DAYTIME HEATING SHOULD HELP TO INCREASE
CONVECTIVE COVERAGE IN THE VICINITY OF THE MCV AND ALONG A LOW
LEVEL CONVERGENCE AXIS/FRONTAL BOUNDARY EXTENDING NORTHEAST FROM
THE MCV INTO N-CNTRL LA.

THE EXPECTATION IS FOR CONVECTION TO INCREASE OVER PORTIONS OF
SERN TX...EAST/NORTHEAST OF THE MCV AND NEAR THE LOW LEVEL
CONVERGENCE AXIS OVER THE NEXT FEW HOURS. LOW TO MID-LEVEL WINDS
OF 10 KT OR LESS SHOULD ENSURE SLOW MOVEMENT TO CONVECTION ALONG
WITH ELEMENTS OF TRAINING. IT IS UNCERTAIN IF ENOUGH INSTABILITY
CAN GROW NEAR THE MCV CENTER THROUGH THE REMAINDER OF THE
AFTERNOON...BUT GIVEN RECENT HEAVY RAINFALL...OVER 5 INCHES IN
PORTIONS OF HARRIS AND FORT BEND COUNTIES OVER THE PAST 24
HOURS...SOME LOCATIONS IN SERN TEXAS ARE HIGHLY SUSCEPTIBLE TO
FLASH FLOOD CONCERNS FROM ADDITIONAL RAINFALL.

OTTO

ATTN...WFO...FWD...HGX...LCH...SHV...

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

LAT...LON   32179307 32139274 31809261 31439322 31009350
            29419391 28629507 28799640 30779634 31919526
            32139388


Last Updated: 224 PM EDT TUE AUG 08 2017