MESOSCALE PRECIPITATION DISCUSSION 0057
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 AM EST WED MAR 09 2016
 
AREAS AFFECTED...SOUTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090800Z - 091030Z
 
SUMMARY...INCREASING CONVECTION IS LIKELY OVER THE NEXT COUPLE OF
HOURS. ISOLATED RUNOFF PROBLEMS/FLASH FLOODING CONCERNS ARE
POSSIBLE THROUGH 10Z...WITH MUCH STRONGER SIGNALS FOR EXCESSIVE
RAIN THEREAFTER.

DISCUSSION...IR SATELLITE IMAGERY SHOWS COOLING CONVECTIVE TOPS
DOWN ALONG THE MIDDLE TX COAST...AND THE TENDENCY OVER THE LAST
HOUR OR SO HAS BEEN FOR A GRADUAL INCREASE IN COVERAGE. MUCH
STRONGER CONVECTION AND HEAVIER RAINS ARE OCCURRING FARTHER NORTH
AND WEST ALONG A FRONTAL ZONE AHEAD OF A WEAK ARE OF LOW
PRESSURE...BUT THERE ARE INDICATIONS THAT CONVECTION WILL
GRADUALLY BECOME MORE FOCUSED ALONG THE CENTRAL AND UPPER TX COAST
APPROACHING 12Z AND BEYOND.

HIRES MODELS INCLUDING MULTIPLE RUNS OF THE HRRR SUGGEST AN
INCREASINGLY FAVORABLE ENVIRONMENT FOR EXPANDING CONVECTION WITH
VERY INTENSE RAINFALL RATES ACROSS THE IMMEDIATE SOUTHEAST TX
COASTAL PLAIN. ALREADY AREA VWP DATA FROM KHGX INDICATES A LOW
LEVEL JET NOW OF 40 TO 45 KTS...WHICH IS FORECAST TO INCREASE TO
50 TO 60 KTS BY 12Z. THIS WILL BE TRANSPORTING A DEEP LAYER OF
SUBTROPICAL MOISTURE NORTHWARD INTO NORTHWESTERN GULF COAST...WITH
PWATS EXPECTED TO REACH AS HIGH AS 1.75 INCHES OVER THE NEXT FEW
HOURS. IN FACT...THE CIRA LAYERED PWAT PRODUCT SHOWS A DUAL
CONFLUENCE ZONE OF MOISTURE INTO SOUTHEAST TX AND SOUTHWEST
LA...WITH A LONG-TRACK FEED FROM THE EASTERN TROPICAL PACIFIC
OCEAN AND ALSO IN FROM THE SOUTHERN GULF OF MEXICO.

THE STRONGER MOISTURE TRANSPORT AND MODEST INSTABILITY INTO THE
REGION COUPLED WITH APPROACHING SHORTWAVE DYNAMICS AND EXCELLENT
UPPER JET SUPPORT SHOULD ALLOW THE CONVECTION TO EXPAND IN
COVERAGE AND INTENSITY.

RAINFALL RATES OF UP TO 2 INCHES/HR OR GREATER ARE EXPECTED WITH
THE MORE INTENSE CORES OVER THE NEXT COUPLE OF HOURS. ANOTHER MPD
WILL BE NEEDED AFTER 10Z ACROSS THIS REGION WHICH WILL ADDRESS THE
EXPECTED LARGER SCALE HEAVY RAINS EXPECTED THIS MORNING OVER
SOUTHEAST TX.

ORRISON

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

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

LAT...LON   31549399 31449371 30699389 29959402 29319463 
            28899526 28439611 28029686 27709723 27709778 
            28109787 28559770 28969755 29419751 29829775 
            30079712 30639613 31109535 31339478