MESOSCALE PRECIPITATION DISCUSSION 0062
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
418 PM EST WED MAR 09 2016
 
AREAS AFFECTED...SOUTHEAST TX...WESTERN LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 092117Z - 100217Z
 
SUMMARY...FLASH FLOOD THREAT WILL CONTINUE...

DISCUSSION...CONVECTION CONTINUES TO STREAM NORTHWARD INTO
SOUTHEAST TX AND WESTERN LA...WITH FLASH FLOODING LIKELY. HEAVIEST
RAINFALL RATES ARE FOCUSING ALONG A LOW LEVEL BOUNDARY...PROBABLY
FOCUSED AROUND 925 MB. STRONG LOW LEVEL INFLOW IS CONVERGING AT
THIS LOCATION RESULTING IN CONTINUOUS TRAINING OF CONVECTION.
NORTH OF THIS BOUNDARY A LACK OF LOW LEVEL INFLOW AND INSTABILITY
IS RESULTING IN LOWER RAINFALL RATES...ALTHOUGH THE STEADY
RAINFALL FALLING ON INCREASING SATURATED GROUND SHOULD CONTINUE TO
CAUSE FLOODING ISSUES ACROSS NORTHEAST TX AND NORTHWEST LA.

PRECIPITABLE WATER VALUES ARE NOW IN THE 1.75"-1.85" RANGE
ALONG/NEAR THIS BOUNDARY AND POINTS SOUTH...WITH 2"+ PWATS
POTENTIALLY MOVING INTO SOUTHEAST TX AND SOUTHWEST LA THIS
EVENING. OTHER THAN THE CONTINUED INCREASE IN MOISTURE...NOT MUCH
HAS CHANGED YET SINCE OUR EARLIER MPD ISSUANCE FOR THIS AREA. THAT
WILL EVENTUALLY CHANGE...AS THE UPPER LOW SLOWLY SHIFTS
NORTHEAST...UPEPR DIVERGENCE IS EXPECTED TO INCREASE...LIKELY
INCREASING CONVECTIVE COVERAGE OVER THE GULF OF MEXICO...WHICH
WILL EVENTUALLY STREAM INLAND. BEGINNING TO SEE THIS INCREASED
MOISTURE/FORCING ON WATER VAPOR IMAGERY ACROSS THE SOUTHWEST GULF.
ALSO BEGINNING TO SEE CONVECTION INCREASE ON RADAR IMAGERY OFF THE
TX COAST. THIS ACTIVITY OFFSHORE SHOULD CONTINUE TO INCREASE IN
COVERAGE...MOVING INTO SOUTHEAST TX TONIGHT...SUCH AS SHOWN BY ALL
THE HIGH RESOLUTION GUIDANCE. IN FACT RECENT TRENDS SUGGEST THE
HIGH RES GUIDANCE MAY BE TOO SLOW BRINGING THIS HEAVIER CONVECTION
SHORE INTO COASTAL TX.

SO REALLY TWO AREAS OF GREATEST CONCERN OVER THE NEXT 6 HOURS. ONE
ACROSS PORTIONS OF WESTERN LA...WHERE TRAINING CONVECTION SHOULD
OCCUR NEAR THE 925 MB BOUNDARY...WITH ADDITIONAL RAINFALL TOTALS
LOCALLY AS HIGH AS 3-5" OVER THE NEXT 6 HOURS...WITH HOURLY TOTALS
UP TO AROUND 1.5" AN HOUR. A CONSENSUS OF THE HIGH RES MODELS
SEEMS TO BE A DECENT STARTING POINT FOR THE HANDLING OF THIS
CONVECTIVE AREA. 

THE SECOND AREA IS ACROSS COASTAL TX...WHERE CONVECTIVE COVERAGE
WILL INCREASE OVER THE NEXT SEVERAL HOURS AS MENTIONED ABOVE.
DESPITE ISSUES EARLIER...CURRENTLY THINK THE HIGH RES GUIDANCE MAY
ACTUALLY BE HANDLING THIS OVERNIGHT ACTIVITY WELL...BRINGING
EXCESSIVE RAINFALL AMOUNTS INTO COASTAL TEXAS. AGAIN THOUGH OUR
MAIN CONCERN IS THAT THIS MAY HAPPEN A BIT EARLIER THAN SUGGESTED
BY THE GUIDANCE. SO AREAS OF COASTAL TX THAT HAVE ESCAPED MUCH OF
THE HEAVIEST RAINFALL SHOULD BEGIN TO SEE AN INCREASING FLOOD
THREAT INTO TONIGHT. 

CHENARD

ATTN...WFO...BRO...CRP...EWX...FWD...HGX...JAN...LCH...LZK...
SHV...

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

LAT...LON   33179209 32789160 31679209 30869286 29779402 
            29489445 29349457 28099580 26469669 26109736 
            26309798 26869816 27669797 28729750 29839677 
            31269633 32499539 33049352