MESOSCALE PRECIPITATION DISCUSSION 0101
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
821 AM EDT MON MAY 18 2015
 
AREAS AFFECTED...PORTIONS OF E-CNTRL TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 181220Z - 181620Z
 
SUMMARY...RAIN RATES OF 2+ IN/HR WITH PERIODS OF TRAINING WILL
LIKELY CONTINUE FOR AT LEAST THE NEXT FEW HOURS...WITH A GRADUAL
SHIFT TOWARD THE NORTHEAST. FLASH FLOODING IS ALREADY OCCURRING
AND WILL LIKELY PERSIST UNTIL AT LEAST 1600 UTC.

DISCUSSION...LATEST IR SATELLITE AND REGIONAL RADAR IMAGERY
CONTINUE TO DEPICT AN EXPANDING AREA OF VERY HEAVY RAINFALL OVER
PORTIONS OF E-CNTRL TEXAS...NORTH OF I-10 AND WEST OF I-45.
OBSERVED RAINFALL RATES OF 2+ IN/HR IN GONZALES COUNTY ARE IN
INDICATION OF THE POTENTIAL OF THE MOIST AIRMASS IN PLACE
CHARACTERIZED BY PRECIPITABLE WATER VALUES OF ROUGHLY 2 INCHES PER
LATEST GPS DATA. 850-700 MB INFLOW OF ROUGHLY 30 KTS IS MAXIMIZED
FROM SRN TEXAS UP THE COASTAL TEXAS PLAIN WHICH IS MEETING OR JUST
EXCEEDING CLOUD BEARING MEAN WIND SPEEDS OF 25-50 KTS. IN
ADDITION...STRONGLY DIFFLUENT FLOW IS PRESENT OVER THE AREA OF
TRAINING CONVECTION WHICH IS HELPING TO INCREASE LIFT.

LATEST DATA FROM THE RAP INDICATE STRONGLY DIFFLUENT FLOW OVER THE
REGION WILL PERSIST THROUGH THE LATE MORNING HOURS...BUT THE
MAGNITUDE OF LOW LEVEL INFLOW WILL WEAKEN PAST 1600 UTC...WHICH IS
EXPECTED TO DISRUPT THE ABILITY CONVECTION TO MAINTAIN TRAINING
POTENTIAL. LATEST HI-RES MODELS ARE SPLIT WITH EXACTLY HOW LONG
HEAVY RAINFALL WILL PERSIST ACROSS THE REGION...BUT RECENT RUNS OF
THE HRRR SEEM TO INDICATE WEAKENING PAST 1600 UTC...COINCIDENT
WITH WEAKENING OF THE LOW LEVEL JET TO NEAR 20 KTS. SOME EXPANSION
OF CONVECTION IS ALREADY OCCURRING TOWARD THE NORTHEAST...MEETING
UP WITH MPD #100...SET TO EXPIRE AT 1404 UTC. THIS MPD WILL
REPLACE #100 AT THAT TIME...AND THE SITUATION WILL BE RE-EVALUATED
NEAR 1600 UTC TO SEE IF ADDITIONAL MESSAGES ARE NEEDED.

OTTO

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

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

LAT...LON   32049401 31679342 31079381 30069486 29529632 
            29449734 29839765 30409752 30999684 31719539 
            32009472