MESOSCALE PRECIPITATION DISCUSSION 0153
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 PM EDT WED JUN 25 2014
 
AREAS AFFECTED...MIDDLE TX COAST 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251603Z - 252203Z
 
SUMMARY...A GROWING MASS OF CONVECTION IS BUILDING WHILE SLOWLY
MOVING ASHORE THE MIDDLE TX COAST.  DESPITE THE HIGH FLASH FLOOD
GUIDANCE VALUES, A FEW SPOTS OF FLASH FLOODING ARE POSSIBLE IN
THIS AREA.

DISCUSSION...AN OUTFLOW BOUNDARY FROM MORNING CONVECTION IS MOVING
DOWN THE TX COAST AT THE PRESENT TIME.  NEAR AND AHEAD OF IT, A
COUPLE THUNDERSTORM COMPLEXES WITH COOLING TOPS ARE DEVELOPING
OVER THE NORTHWEST GULF OF MEXICO, WITH THUNDERSTORMS STARTING TO
ROLL INLAND.  THE 0-6 KM SHEAR IS NEAR 25 KTS PER THE 14Z RAP,
INDICATING THAT ORGANIZED CONVECTION IS POSSIBLE IN THIS REGION. 
PRECIPITABLE WATER VALUES OF 2-2.25" ARE MOVING INTO THE REGION,
WHICH ARE ABOVE THE 90TH PERCENTILE FOR LATE JUNE.  CAPES OF
2000-3000 J/KG ARE DRIVING THE ACTIVITY.  THE WET BULB ZERO HEIGHT
IN THE 12Z CORPUS CHRISTI AND LAKE CHARLES SOUNDINGS WAS ~14,500
FEET -- HIGH ENOUGH THAT WARM RAIN PROCESSES COULD BE AT PLAY
WHICH COULD LEAD TO RAINFALL AMOUNTS EXCEEDING RADAR ESTIMATES.

THE EXPECTATION IS THAT THE OUTFLOW BOUNDARY FROM SOUTHEAST TX
WILL DRIFT SOMEWHAT FURTHER DOWN THE COAST, AND THAT THE ACTIVITY
FROM THE GULF OF MEXICO MOVING INLAND WILL SET UP A COASTAL
CONVERGENCE ZONE DUE TO THE RAIN-COOLED AIR SETTING UP INLAND AND
THE CAPES BECOMING EXHAUSTED ASHORE.  CORFIDI VECTORS ALMOST
DIRECTLY OPPOSE CELL MOTION AND THE WEAK LOW-LEVEL INFLOW, WHICH
COULD LEAD TO SLOW THUNDERSTORM MOVEMENT.  RAINFALL RATES UP TO 3"
AN HOUR ARE POSSIBLE HERE IN STRONGER/MORE EFFICIENT STORMS. 
SEVERAL PIECES OF MESOSCALE GUIDANCE -- THE LAST COUPLE HRRR RUNS,
THE 06Z CANADIAN REGIONAL, THE 12Z PARALLEL NAM CONEST, AND A
SIGNAL WITHIN THE 00Z SPC WRF INDICATE THAT LOCAL AMOUNTS OF 6-8"
ARE POSSIBLE HERE.  DESPITE THE HIGH FLASH FLOOD GUIDANCE VALUES,
A FEW SPOTS COULD RECEIVE FLASH FLOODING WITHIN THE DEFINED AREA.

ROTH

ATTN...WFO...HGX...CRP...EWX...BRO...

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

LAT...LON   29659573 29359699 28659784 27599794 26919746 27669712
            28249651 28899523 29619450 29659573