MESOSCALE PRECIPITATION DISCUSSION 0623
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 PM EDT FRI OCT 30 2015
 
AREAS AFFECTED...EAST-CENTRAL TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 301951Z - 310000Z
 
SUMMARY...VERY INTENSE SHOWERS AND THUNDERSTORMS CONTINUE OVER
PORTIONS OF EAST-CENTRAL TX...WITH ADDITIONAL FLASH FLOODING
CONCERNS EXPECTED TO PERSIST.

DISCUSSION...MULTIPLE CLUSTERS OF INTENSE SHOWERS AND
THUNDERSTORMS CONTINUE TO IMPACT PORTIONS OF CENTRAL AND EASTERN
TX THIS AFTERNOON WHICH HAVE ALREADY PRODUCED LOCALLY VERY
SIGNIFICANT FLASH FLOODING...INCLUDING AREAS IN AND AROUND THE
AUSTIN TX AREA AND COMMUNITIES TO THE SOUTH AND EAST. THE LATEST
RADAR TRENDS SHOW SOME TENDENCY OVER THE LAST HOUR FOR THE CLUSTER
OF CONVECTION MOVING NORTHEAST OF A LINE FROM AUSTIN TO FORT HOOD
TO WEAKEN A BIT AND TO BECOME A BIT LESS ORGANIZED. THIS IS
PRIMARILY THE RESULT OF THE CONVECTION LIFTING NORTHEAST INTO A
RELATIVELY MORE STABLE BOUNDARY LAYER AS IT IS OVERRUNNING A
SURFACE FRONTAL ZONE THAT HAS BEEN ATTEMPTING TO LIFT NORTH AS A
WARM FRONT.

NEVERTHELESS...A DIVERGENT FLOW REGIME ALOFT AHEAD OF AN UPPER
TROUGH IS INTERACTING WITH A WELL-DEFINED AND DEEP TROPICAL
AIRMASS. THE LATEST CIRA LAYERED PW PRODUCT SHOWS WELL-DEFINED
CHANNELS OF EASTERN PACIFIC OCEAN AND GULF OF MEXICO MOISTURE
FUNNELING NORTH INTO CENTRAL AND EASTERN TX...WHICH HAS BEEN
CONTRIBUTING TO IMPRESSIVELY HIGH GPS-DERIVED PWATS OF 2.0 TO 2.2
INCHES. THE STRONGER FORCING ALOFT COUPLED WITH THE TRANSPORT OF
VERY MOIST AND RELATIVELY UNSTABLE AIR IS LIKELY TO CONTINUE TO
FOCUS CONVECTION NEAR AND JUST NORTH OF THE AFOREMENTIONED FRONTAL
ZONE.

HOWEVER...THE LATEST HRRR AND 12Z ARW/12Z NMMB GUIDANCE SUGGESTS
SOMEWHAT LESS ORGANIZATION OVER THE NEXT FEW HOURS...WITH
ADDITIONAL RAINFALL AMOUNTS OF 2 TO 4 INCHES LOCALLY THROUGH 00Z.
THEREFORE...THE ADDITIONAL FOCUS FOR FLASH FLOODING MAY TEND TO BE
MORE LOCALIZED...BUT GIVEN EARLIER RAINS AND A HISTORY OF
REPEATING CELLS...THE POTENTIAL FOR SIGNIFICANT RUNOFF PROBLEMS
WILL REMAIN.

ORRISON

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

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

LAT...LON   32099621 31729575 31139582 30799596 30169644 
            29729722 29399801 29379835 29659875 30089888 
            30899842 31439787 31969703