MESOSCALE PRECIPITATION DISCUSSION 0767
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
459 PM EST SUN NOV 06 2016
 
AREAS AFFECTED...PORTIONS OF CNTRL TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 062158Z - 070358Z
 
SUMMARY...FLASH FLOODING IS EXPECTED TO BE A CONCERN FOR PORTIONS
OF CNTRL TX TOWARD THE MIDDLE TX COAST LATER THIS EVENING INTO
OVERNIGHT. REPEATING RAINFALL RATES OF 1-2 IN/HR MAY LEAD TO
LOCALIZED 6 HOUR RAINFALL TOTALS OF 3-5 INCHES.

DISCUSSION...TRENDS IN RADAR OVER THE PAST 1-2 HOURS HAVE SHOWN
WEAKENING INTENSITIES FROM A FORWARD PROPAGATING LINE OF
THUNDERSTORMS CURRENTLY SAGGING SOUTH TOWARD I-10 BETWEEN AUS AND
3T5. AN OUTFLOW BOUNDARY WAS IDENTIFIED AHEAD OF THE BOWING
LINE...WITH THE WRN END NEARLY STATIONARY...LOCATED JUST NORTH OF
BAZ AND KRV. SLOW MOVING SHOWERS HAVE ALSO DEVELOPED SOUTH OF THE
OUTFLOW AND HAVE BEEN DRIFTING NORTH. THE IMMEDIATE FLASH FLOOD
CONCERN IS WITH CELL MERGERS...HOWEVER THESE WILL LARGELY IMPACT
LOCATIONS THAT HAVE BEEN DRY IN RECENT WEEKS. A PRECIPITABLE WATER
MAX OF ROUGHLY 1.50 TO 1.75 INCHES WAS LOCATED OVER SOUTH
TEXAS...WHICH IS THE SOURCE REGION FOR 850 MB MOISTURE
ADVECTION...CURRENTLY 20-25 KT FROM THE SOUTH. 

A SLIGHT INCREASE IN LOW LEVEL FLOW IS EXPECTED NEAR AND BEYOND
00Z ALONG WITH THE APPROACH OF A 70-90 KT JET STREAK...CURRENTLY
APPROACHING FROM THE WEST OVER NWRN MEXICO. THE LEFT EXIT REGION
OF THIS JET STREAK IS EXPECTED TO INCREASE DIVERGENCE OVER THE
ALREADY DIFFLUENT REGION OF CNTRL TX TOWARD THE END OF THE MPD
EXPIRATION TIME...03-04Z. MOISTURE OVERRUNNING THE OUTFLOW OR
NEWLY DEVELOPED OUTFLOWS MAY LEAD TO REPEATING ROUNDS OF HEAVY
RAIN OVER THE SAME LOCATION. 

THE HI-RES GUIDANCE HAS STRUGGLED WITH THE EVOLUTION OF RAINFALL
ALL AFTERNOON...AND WHILE THE HRRR HAS BEEN CLOSEST...IT TOO MAY
BE MISSING OUT ON MESOSCALE BOUNDARY INTERACTIONS. ONE POSSIBLE
SCENARIO IS CELL MERGERS GENERATE NEW OUTFLOW WHICH BECOMES
OVERRUN FARTHER SOUTH NEAR VCT AND MATAGORDA BAY...LATER TONIGHT.
GIVEN DRIER ANTECEDENT CONDITIONS ACROSS LOCATIONS NEARER TO THE
GULF COAST...AND UNCERTAINTIES IN EVOLUTION...FLASH FLOODING IS
ONLY POSSIBLE.

OTTO

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

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

LAT...LON   30989629 30749565 29859520 29019561 28759701 
            28889821 29579873 30219844 30269746 30849679