MESOSCALE PRECIPITATION DISCUSSION 0077
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
423 AM EDT MON MAY 11 2015
 
AREAS AFFECTED...CNTRL TO ERN TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 110823Z - 111300Z
 
SUMMARY...FLASH FLOODING REMAINS POSSIBLE ACROSS PORTIONS OF CNTRL
TO ERN TEXAS AS MOIST/LOW LEVEL FLOW CONTINUES TO OVERRUN A
SOUTHWARD SAGGING OUTFLOW BOUNDARY. ADDITIONAL RAINFALL TOTALS OF
2 TO 4 INCHES WITH LOCALLY AS HIGH AS 7 INCHES WILL BE POSSIBLE
THROUGH 13Z. 

DISCUSSION...AT 08Z...AN ELONGATED OUTFLOW BOUNDARY EXTENDED NEWD
ACROSS CNTRL TO ERN TEXAS...AND NWD INTO CNTRL ARKANSAS. THIS
BOUNDARY HAS BEEN MAKING STEADY FORWARD PROGRESS ACROSS THE I-35
AND I-45 CORRIDORS OVER THE PAST 2 HOURS WHICH HAS ALLOWED A LULL
IN OBSERVED 1 AND 3 HOUR RAINFALL RATES WITHIN EMBEDDED TRAINING
HEAVY RAINFALL CORES. HOWEVER...PRECIPITABLE WATER VALUES REMAIN
HIGH...WITH POTENTIAL FOR HEAVY DOWNPOURS...AS SEEN EARLIER THIS
MORNING ACROSS NAVARRO AND HENDERSON COUNTIES WHERE AN ESTIMATED
10 - 15 INCHES OF RAIN HAS FALLEN SINCE 00Z. 

850 MB WINDS ARE FORECAST BY THE RAP TO WEAKEN THROUGH 12Z...AS
SEEN BY KGRK VAD WIND DECREASE FROM 35 TO 25 KTS OVER THE PAST 2
HOURS. THIS DECREASE WILL BE COINCIDENT WITH THE LIFTING OF A
MID-UPPER LEVEL TROUGH AXIS CURRENTLY OVER S-CNTRL OKLAHOMA AS
SEEN ON WATER VAPOR IMAGERY AND DIURNAL WEAKENING. HOWEVER...HIGH
MOISTURE CONTENT AIR AND REMAINING FAVORABLE SETUP FOR TRAINING
WILL CONTINUE OVER THE NEXT FEW HOURS. 

TWO MITIGATING FACTORS TO FLASH FLOODING INCLUDE THE FACT THAT THE
HIGHLIGHTED THREAT REGION HAS NOT RECEIVED NEARLY AS MUCH RAINFALL
OVER THE PAST WEEK COMPARED TO LOCATIONS FARTHER NORTH. IN
ADDITION...WEAKENING 850 MB FLOW THROUGH 13Z WILL LIMIT THE DEGREE
OF OVERRUNNING AVAILABLE TO THE SOUTHWARD SINKING OUTFLOW
BOUNDARY. THE PAST FEW RUNS OF THE HRRR...ESRL'S EXPERIMENTAL HRRR
AND 00Z NMM/ARW SUGGEST AN ADDITIONAL 2-4 INCHES WITH LOCALLY UP
TO AS MUCH AS 10 INCHES BY 13Z. WHILE 10 INCHES SEEMS UNLIKELY
GIVEN THE WEAKENING SETUP...AMOUNTS AS HIGH AS 7 INCHES ON A
LOCALIZED BASIS DO NOT SEEM OUT OF THE QUESTION. 

OTTO

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...SJT...

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

LAT...LON   32659490 32409408 31569404 30579465 29939635 
            29609937 30309967 31149731 31679614