MESOSCALE PRECIPITATION DISCUSSION 0093
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
537 PM EDT SUN APR 02 2017

AREAS AFFECTED...SERN LA INTO NERN LA/SWRN AR/WRN MS

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

VALID 022137Z - 030330Z

SUMMARY...FLASH FLOODING...SOME POTENTIALLY SIGNIFICANT...IS
EXPECTED IN A SW TO NE AXIS...EXTENDING FROM SERN TX...THROUGH
CNTRL LA INTO WRN MS/SERN AR. TRAINING OF HEAVY RAIN WITH 3-HRLY
RATES OF 3-5 INCHES WILL BE POSSIBLE.

DISCUSSION...RECENT RADAR TRENDS THROUGH 21Z HAVE SHOWN THE
SLOWING OF A SW TO NE ORIENTED AXIS OF HEAVY RAIN OVER SERN TX
WITH DUAL-POL ESTIMATED RAINFALL RATES OVER 2 IN/HR. WHILE A BROAD
AREA OF PRECIPITABLE WATER...PWAT...VALUES GREATER THAN 1.7 INCHES
EXTENDING ACROSS THE UPPER TX COAST INTO MUCH OF LA AND SRN
AR...19Z GPS PWAT VALUES WERE 1.8 TO 1.9 INCHES FROM LCH TO ESF
AHEAD OF THE TRAINING AXIS IN TX. OTHER AXES OF HEAVY RAIN
DEPICTED ON RADAR WERE ALIGNED WELL WITH 850 MB
STREAMLINES...CONVERGING ACROSS CNTRL TO NRN LA.

AS AN 850 MB LOW OBSERVED VIA VAD WIND PLOTS OVER N-CNTRL TX AND
AN MCV OVER SRN AR TRACK NNEWD OVER THE NEXT 3-6 HOURS...THE NRN
PORTION OF A BOWING SQUALL LINE ACROSS THE LA/AR BORDER SHOULD
CONTINUE TO PROGRESS TOWARD THE EAST. HOWEVER...THE SRN FLANK IS
EXPECTED TO STALL OR ONLY SLOWLY PROPAGATE EWD INTO LA OVER THE
NEXT SEVERAL HOURS. INCREASING UPPER DIFFLUENCE ACROSS LA AHEAD OF
AN APPROACHING UPPER LOW LOCATED OVER WRN TX SHOULD SUPPORT ONE OR
TWO AXES OF VERY HEAVY...TRAINING RAINFALL ANYWHERE FROM SERN TX
THROUGH CNTRL LA REACHING SERN AR AND WRN MS. THE POTENTIAL FOR
3-5 INCHES OF RAIN IN 3 HRS WILL MAKE FLASH FLOODING LIKELY WITHIN
THE MPD THREAT AREA.

WHILE MOST OF THE HI-RES GUIDANCE HAS BEEN TOO SLOW WITH THE
PROPAGATION OF THE ONGOING SQUALL LINE...MANUALLY ADJUSTED OUTPUT
FROM THE 12Z NSSL WRF AND RECENT RUNS OF THE HRRR SHOW A
CONSISTENT SIGNAL FOR SIGNIFICANT ADDITIONAL RAINFALL WITH TOTALS
POSSIBLY EXCEEDING 7 INCHES IN ONE OR TOW LOCATIONS BY 04Z.

OTTO

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

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

LAT...LON   33659103 32869037 31389080 30069191 29939317
            29999416 30079438 30169455 30379460 30619436
            30829397 31069361 31709303 32579251 33379196