Graphic for MPD #0111

MESOSCALE PRECIPITATION DISCUSSION 0111
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EDT TUE APR 11 2017

AREAS AFFECTED...SOUTH-CENTRAL TO SOUTHEAST TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 111730Z - 112230Z

SUMMARY...SLOW-MOVING THUNDERSTORMS WITH VERY HEAVY RAIN ARE
EXPECTED TO EXPAND IN COVERAGE OVER THE NEXT FEW HOURS.

DISCUSSION...THE LATEST SATELLITE AND RADAR IMAGERY SHOWS A
GRADUAL EXPANSION AND ORGANIZATION OF THUNDERSTORMS ACROSS THE TX
HILL COUNTRY AND EXTENDING EAST TOWARD THE SOUTHEAST TX COASTAL
PLAIN. THE CONVECTION IS DEVELOPING ALONG AND JUST SOUTH OF A
SLOW-MOVING COLD FRONT...AND WITH SUPPORT FROM AN APPROACHING
SHORTWAVE TROUGH. MEANWHILE...STRONG DIURNAL HEATING SOUTH OF THE
BOUNDARY IS FOSTERING A ROBUST UPTICK IN BOUNDARY LAYER
INSTABILITY...WITH MLCAPE VALUES ALREADY APPROACHING 2000 J/KG
OVER SOUTH-CENTRAL TX.

OVER THE NEXT FEW HOURS...CONVECTION SHOULD CONTINUE TO EXPAND IN
COVERAGE AND BECOME BETTER ORGANIZED AS THE UPSTREAM ENERGY
INTERACTS WITH AN INCREASINGLY FAVORABLE THERMODYNAMIC ENVIRONMENT
GIVEN THE STRONG DAYTIME HEATING AND AN ALREADY MOIST AIRMASS
CHARACTERIZED BY PWATS NEAR 1.5 INCHES.

THE STEERING FLOW IS RELATIVELY WEAK AT THIS TIME WHICH WILL
RESULT IN SLOW CELL MOTION...HOWEVER AS CONVECTION INCREASES IN
ORGANIZATION THERE SHOULD BE A TENDENCY TO BUILD UP A SUFFICIENT
COLD POOL FOR CONVECTION TO BEGIN BOWING/PROPAGATING MORE
PROGRESSIVELY TO THE SOUTHEAST.

THE 12Z ARW/NMMB SOLUTIONS AND TO AN EXTENT THE LATEST HRRR
GUIDANCE SHOW A DISTINCT LACK OF CONVECTIVE ORGANIZATION THIS
AFTERNOON OVER SOUTH-CENTRAL TX. GIVEN THE THERMODYNAMIC TRENDS
AND THE UPSTREAM ENERGY IT APPEARS THAT THE THUNDERSTORM ACTIVITY
WILL TEND TO BE A BIT MORE WIDESPREAD THROUGH THE AFTERNOON.

EXPECT RAINFALL RATES OF UP TO 3 INCHES/HR BASED ON THE LEVEL OF
MOISTURE/INSTABILITY POOLING AHEAD OF THE COLD FRONT. THIS COUPLED
WITH THE SLOW CELL MOTION WILL PROMOTE LOCALLY VERY HEAVY STORM
TOTALS THAT MAY APPROACH OR LOCALLY EXCEED 5 INCHES. FLASH
FLOODING AS A RESULT WILL BE POSSIBLE.

ORRISON/MCDONNAL

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SJT...

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

LAT...LON   31049931 30639745 30519652 30559593 30649492
            30539375 29969374 29569417 29259477 28849545
            28669602 28769725 29129847 29739963 30340003
            30869986


Last Updated: 131 PM EDT TUE APR 11 2017