Graphic for MPD #0549

MESOSCALE PRECIPITATION DISCUSSION 0549
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
456 AM EDT MON JUL 24 2017

AREAS AFFECTED...ERN TX INTO CNTRL LA/SWRN MS

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

VALID 240855Z - 241400Z

SUMMARY...SCATTERED FLASH FLOODING WILL BE POSSIBLE FROM PORTIONS
OF ERN TX INTO CNTRL LA AND SWRN MS WITH SLOW CELL MOVEMENT
CONTAINING RAINFALL RATES OF 2-3 IN/HR. THE THREAT IS EXPECTED TO
SLOWLY INCREASE DURING THE EARLY MORNING HOURS.

DISCUSSION...SURFACE OBSERVATIONS PLACED AN OUTFLOW BOUNDARY
ARCING ROUGHLY WEST TO EAST ACROSS CNTRL AND ERN TX...WHICH HAS
BEEN RESPONSIBLE FOR RECENT THUNDERSTORM ACTIVITY OVER
HOUSTON...TRINITY AND ANGELINA COUNTIES WITH RADAR ESTIMATED
RAINFALL RATES SURPASSING 2 IN/HR AS OF 0840Z. OTHER SCATTERED
THUNDERSTORM ACTIVITY WAS NOTED ACROSS SWRN MS...IN THE VICINITY
OF A WEAK 700-500 MB TROUGH AXIS. THE ENTIRE REGION FROM EAST
TEXAS INTO SWRN MS IS CAUGHT IN A LARGE-SCALE COL IN THE MID-UPPER
FLOW ALLOWING FOR WEAK CELL MOTIONS. HOWEVER...VAD WIND PLOTS AT
KPOE AND KLCH CONFIRMED RECENT RAP FORECASTS OF RELATIVELY
STRONGER WLY 850 MB FLOW RANGING BETWEEN 15 AND 25 KT. GPS
PRECIPITABLE WATER VALUES RANGED FROM 1.9 TO 2.2 INCHES FROM 06Z
OVER THE ENTIRE REGION...WHICH SHOULD HELP COMPENSATE FOR WEAK
CAPE VALUES ESTIMATED TO BE BETWEEN 500 AND 1000 J/KG BASED ON
RECENT OUTPUT FROM THE SPC MESOANALYSIS PAGE.

THE EXPECTATION IS FOR THUNDERSTORM ACTIVITY TO INCREASE FROM
PORTIONS OF EAST TX INTO CNTRL LA AND SWRN MS OVER THE NEXT FEW
HOURS IN THE VICINITY OF WEAK UPPER FORCING. LITTLE CIN IN RAP
ANALYSIS SOUNDINGS MAY ALSO SUPPORT RAPID CELL DEVELOPMENT AFTER
SUNRISE. CELL MOVEMENT IS EXPECTED TO BE SLOW TOWARD THE
EAST...BUT STRONGER LOW LEVEL FLOW NOTED ABOVE SHOULD SUPPORT
TRAINING AND BACK BUILDING OF CONVECTION LEADING TO VERY HEAVY
RAINFALL RATES OF 2-3 IN/HR. THIS MAY LEAD TO A FEW AREAS OF FLASH
FLOODING DURING THE EARLY MORNING HOURS...ESPECIALLY IF COVERAGE
INCREASES OVER PORTIONS OF LA INTO MS WHERE FFG VALUES ARE
LOWERED...1.5 TO 3 INCHES IN 3 HOURS FOR A FEW LOCATIONS.

THIS SCENARIO HAS BEEN WELL ADVERTISED IN A MAJORITY OF THE 00Z
CAM GUIDANCE ALONG WITH THE PAST FEW RUNS OF THE HRRR AND ESRL
EXPERIMENTAL HRRR...HOWEVER THE COVERAGE IN THE HRRRS COULD BE TOO
LARGE BASED ON RECENT RADAR TRENDS. STILL...THE AREA IS WORTH
WATCHING FOR POSSIBLE FLASH FLOODING.

OTTO

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

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

LAT...LON   32249085 31328945 30638965 30209104 30399274
            30869599 31629635 32119505


Last Updated: 456 AM EDT MON JUL 24 2017