MESOSCALE PRECIPITATION DISCUSSION 0182
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
107 PM EDT WED MAY 03 2017

AREAS AFFECTED...FAR SOUTHEASTERN TX/SOUTHERN LA...

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

VALID 031706Z - 032106Z

SUMMARY...FLASH FLOODING WILL BE LIKELY FROM FAR SOUTHEASTERN TX
EASTWARD ACROSS MUCH OF SOUTHERN LA THROUGHOUT THE AFTERNOON. AN
ONGOING TRAINING CONVECTION EVENT IS UNDERWAY WHICH HAS GENERALLY
STRADDLED INTERSTATE 10. GIVEN AMPLE INSTABILITY/MOISTURE COUPLED
WITH A BOUNDARY TO LATCH ONTO...EXPECT FLASH FLOODING PARTICULARLY
IN LOCATIONS WHICH HAVE SEEN HEAVY RAINFALL THIS MORNING.

DISCUSSION...THE 17Z FRONTAL ANALYSIS DEPICTED A BOUNDARY
EXTENDING FROM THE VICINITY OF NEW ORLEANS LA WESTWARD INTO
SOUTHWESTERN LA/SOUTHEASTERN TX. RECENT BLENDED-TPW IMAGERY SHOWED
A WELL DEFINED MOISTURE PLUME SURGING NORTHWARD OUT OF THE WESTERN
GULF OF MX. PRECIPITABLE WATER VALUES IN EXCESS OF 1.75 INCHES
WERE COMMONPLACE ALONG THE UPPER TX AND LA COASTLINES. AN
IMPRESSIVE 850-MB DEW POINT GRADIENT WAS NOTED IN THE 16Z RAP
OBJECTIVE ANALYSIS WITH 15 TO 17C VALUES OBSERVED OVER MUCH OF THE
MPD AREA WHILE NUMBERS FALL OFF BY NEARLY 10C TOWARD NORTHEASTERN
LA. ABUNDANT INSTABILITY REMAINS ACROSS THE INFLOW REGION WITH
OVER 3000 J/KG OF UNCAPPED AIR STREAMING TOWARD THE WARM FRONTAL
ZONE. THERE APPEARS TO BE A PARTICULAR FOCUS ALONG THE TX/LA
BORDER WHERE 3 TO 6 INCHES OF RAINFALL HAS FALLEN PER RADAR
ESTIMATES. THERE HAS ALREADY BEEN AN OBSERVATION OF OVER 6 INCHES
IN JASPER COUNTY TX WITH A NUMBER OF FLASH FLOOD REPORTS WHICH
INCLUDES SOME IMPASSABLE HIGHWAYS.

THERE IS A STRONG HIGH-RESOLUTION MODEL SIGNAL TO MAINTAIN THE
ONGOING ACTIVITY WHILE GRADUALLY LIFTING IT NORTHWARD IN TIME.
THIS SHOULD GENERALLY FOLLOW THE POLEWARD MIGRATION OF THE
OBSERVED WARM FRONT. EVENTUALLY THE ACTIVITY MAY BECOME MORE
PROGRESSIVE AS AN UPSTREAM COLD FRONT APPROACHES THE REGION FROM
THE WEST. UNTIL THEN...EXPECT AN INCREASED THREAT OF FLASH
FLOODING THROUGH MUCH OF THE AFTERNOON.


RUBIN-OSTER

ATTN...WFO...HGX...LCH...LIX...

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

LAT...LON   31079309 30959245 30729151 30339083 29919071
            29499094 29479163 29769279 29979377 29869456
            30609471 31039374