MESOSCALE PRECIPITATION DISCUSSION 0129
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1055 AM EDT MON APR 18 2016
 
AREAS AFFECTED...SOUTHEAST TX...SOUTHWEST LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 181452Z - 181900Z
 
SUMMARY...VERY INTENSE RAINFALL WILL CONTINUE ACROSS SOUTHEAST TX
THOUGH EARLY AFTERNOON AS SHOWERS AND THUNDERSTORMS PERSIST.

DISCUSSION...THE LATEST GOES-14 SRSO VIS IMAGERY SHOWS AN
EXPANSIVE AREA OF THUNDERSTORMS ACROSS SOUTHEAST TX WHICH ARE
PRODUCING VERY INTENSE RAINFALL RATES. ALREADY THERE HAVE BEEN
OBSERVATIONS OF 15 TO 20 INCHES OF RAIN ACROSS THE NORTHWEST
SUBURBS OF THE HOUSTON METROPOLITAN AREA GOING BACK TO LAST
EVENING GIVEN THE INCREDIBLY SLOW MOVEMENT AND REPEATING NATURE OF
THE CONVECTION.

THERE HAS BEEN SOME EVIDENCE OF A GRADUAL SOUTH AND EAST PUSH TO
THE CONVECTION OVER THE LAST COUPLE OF HOURS...AND THE GOES-14
SRSO VIS IMAGERY SHOWS A WELL-DEFINED OUTFLOW BOUNDARY
REPRESENTING THE LEADING EDGE OF THE CONVECTION. LARGER SCALE
FORCING CONTINUES OVER THE REGION AS RIGHT-ENTRANCE REGION JET
FORCING IS IN PLACE ASSOCIATED WITH A 90-110 KT JET MAX RIDING UP
THE EASTERN FLANK OF THE UPPER LOW OVER THE CENTRAL ROCKIES.
MEANWHILE...THERE CONTINUES TO BE A FEED OF VERY MOIST AND RATHER
UNSTABLE AIR LIFTING NORTH OUT OF THE WESTERN GULF OF MEXICO.
PWATS OF 1.7 TO 1.9 INCHES AND MUCAPE VALUES OF 2000 TO 2500 J/KG
ARE NOTED OVER THE WESTERN GULF OF MEXICO AND THIS WILL CONTINUE
TO LIFT NORTH INTO OUTFLOW BOUNDARY AND WILL SUSTAIN CONVECTIVE
DEVELOPMENT OVER THE NEXT SEVERAL HOURS WITH VERY SLOW CELL MOTION.

THE HIRES MODELS HAVE BEEN DOING A VERY POOR JOB IN ACCURATELY
DEPICTING THE CONVECTIVE EVOLUTION THIS MORNING...BUT ONE AREA OF
AGREEMENT IS THAT THERE SHOULD A TENDENCY FOR CONVECTION TO LOSE
SOME OF ITS ORGANIZATION GOING THROUGH EARLY AFTERNOON. THIS WILL
BE A RESULT OF THE AFOREMENTIONED JET DYNAMICS ALOFT STARTING TO
LIFT OUT TO THE NORTH AND AWAY FROM SOUTHEAST TX COUPLED WITH SOME
DECREASE IN THE LOW LEVEL INFLOW OFF THE GULF OF MEXICO.
NEVERTHELESS...EXPECT ADDITIONAL RAINFALL RATES OF UP TO 3
INCHES/HR...AND ADDITIONAL TOTALS LOCALLY OF UP TO 6 INCHES GOING
THROUGH 19Z. THIS WILL LIKELY PRODUCE SIGNIFICANT FLASH FLOODING.

ORRISON

ATTN...WFO...CRP...EWX...HGX...LCH...SHV...

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

LAT...LON   31199408 30979317 30149308 29399396 28659566 
            28309745 28419884 28799927 29239909 29739810 
            30009623 30739475