MESOSCALE PRECIPITATION DISCUSSION 0084...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1032 PM EDT THU MAY 14 2015
 
CORRECTED FOR TYPO FOUND IN TEXT IN THE GRAPHIC

AREAS AFFECTED...SOUTH-CENTRAL TX... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 150231Z - 150716Z
 
SUMMARY...INCREASING CONFIDENCE IN A HEAVY RAINFALL EVENT LEADING
TO THE POSSIBILITY OF FLASH FLOODING. BELIEVE THE THREAT WILL
CONTINUE THROUGH AT LEAST 12Z.

DISCUSSION...THE BLENDED-TPW PRODUCT THIS EVENING SHOWED AN
IMPRESSIVE SLUG OF TROPOSPHERIC MOISTURE WORKING ITS WAY UP THE
RIO GRANDE. THIS HAS LOCALLY RAISED PWAT VALUES TO ABOVE 1.50
INCHES ACROSS SOUTH TX. A BROAD AMOUNT OF CONVECTION IS STILL
ONGOING TO THE EAST OF THE MPD AREA. HOWEVER...THIS ACTIVITY IS
WANING AS INSTABILITY HAS BEEN RAPIDLY DECREASING. MEANWHILE...THE
01Z RAP OBJECTIVE ANALYSIS SHOWED AN EXPANSIVE PLUME OF 2000 TO
3000 J/KG OF MLCAPE STRETCHING ALONG THE LOWER RIO GRANDE UP
TOWARD THE BIG BEND. THE 00Z DRT RAOB CONFIRMS THESE FINDINGS WITH
OVER 3000 J/KG OF CAPE AND VERY STEEP MID-LEVEL LAPSE RATES.
CONVECTION HAS ALREADY BEGUN TO FIRE IN THIS UNCAPPED ENVIRONMENT
WITH CELL MOTIONS RATHER SLOW. EXPECT THE COVERAGE OF CONVECTION
TO EXPAND OVERNIGHT LEADING TO 1 TO 2 INCH HOURLY RAINFALL RATES
WHICH MAY SUPPORT AREAS OF FLASH FLOODING.

THERE IS A STRONG SIGNAL IN THE CONVECTION-ALLOWING MODELS OF VERY
HEAVY RAINFALL EAST OF THE BIG BEND. WHILE THE GUIDANCE VARIES IN
LOCATION...THE IDEA OF INTENSE/SLOW-MOVING CONVECTION OCCURRING IS
SUPPORTED BY THE LATEST OBSERVATIONAL DATA. THUS...1/3-HOUR FFG
VALUES MAY BE EXCEEDED IN PORTIONS OF THE MPD AREA.


RUBIN-OSTER

ATTN...WFO...CRP...EWX...SJT...

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

LAT...LON   30610112 30569994 29679913 28859888 28279914 
            28230018 29060067 29460107 29840159 30340159