MESOSCALE PRECIPITATION DISCUSSION 0585
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
503 PM EDT SAT AUG 20 2016
 
AREAS AFFECTED...SOUTH-CENTRAL TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 202100Z - 210100Z
 
SUMMARY...EXTREMELY HEAVY RAINS ARE EXPECTED OVER THE NEXT FEW
HOURS ACROSS PORTIONS OF THE TX HILL COUNTRY NORTH OF SAN ANTONIO
AND ESPECIALLY NEAR THE AUSTIN AREA. FLASH FLOODING IS LIKELY.

DISCUSSION...A VERY WELL-DEVELOPED MCV IS BECOMING CONVECTIVELY
MORE ACTIVE AS PER TRENDS SEEN IN THE LATEST VISIBLE AND IR
SATELLITE IMAGERY. CLOUD TOPS ARE COOLING NEAR THE VORT
CENTER...AND THERE IS SUGGESTION OF OVERSHOOTING TOP DEVELOPMENT
BASED ON CLOUD TOP COOLING MAGNITUDES SEEN OVER THE LAST 30
MINUTES.

VERY HEAVY RAINFALL IS FOCUSING AND BECOMING CONCENTRATED IN
PARTICULAR JUST WEST OF THE AUSTIN/GEORGETOWN TX AREAS...AND
ADJACENT AREAS OF THE TX HILL COUNTRY ARE LIKELY TO SEE A
PARTICULARLY FAVORABLE ENVIRONMENT APPROACHING THE EVENING HOURS
FOR SIGNIFICANT RAINFALL TOTALS.

PWATS ARE ALREADY LOCALLY NEAR 2.25 INCHES...AND WITH SUCH A DEEP
MOIST COLUMN...THE CONVECTION WILL BE EXTREMELY EFFICIENT IN
GENERATING ENHANCED RAINFALL RATES THAT MAY APPROACH OR EXCEED 3
INCHES/HR.

THE CONVECTION SHOULD FOCUS NEAR AND AHEAD OF A COLD FRONT
APPROACHING THE REGION...BUT WILL BE ENHANCED DYNAMICALLY BY THE
MCV AND AN INCREASINGLY UNSTABLE AIRMASS JUST TO THE SOUTH AND
EAST OF IT.

THROUGH EARLY EVENING...WITH THE MCV DRIFTING VERY SLOWLY
EAST-NORTHEAST...ADDITIONAL RAINFALL AMOUNTS APPROACHING 5 INCHES
IS EXPECTED. FLASH FLOODING IS LIKELY...SOME OF IT
SIGNIFICANT...THROUGH THE LATE AFTERNOON AND EARLY EVENING
HOURS...AND ESPECIALLY NEAR THE URBANIZED AREAS NORTH OF SAN
ANTONIO CLOSE TO AUSTIN AND GEORGETOWN.

ORRISON

ATTN...WFO...EWX...FWD...HGX...

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

LAT...LON   31119722 30829648 30109639 29609682 29379724 
            29189827 29499873 29919861 30289881 30529878 
            30769870 30919846