MESOSCALE PRECIPITATION DISCUSSION 787
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
114 AM EST MON DEC 5 2016
 
AREAS AFFECTED...SOUTHERN TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 050611Z - 051201Z
 
SUMMARY...NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED OVER
SOUTHERN TEXAS NEAR THE GULF COAST THROUGH 12Z MONDAY.  PERIODS OF
HEAVY RAINFALL LIKELY WITH 1 TO 3 INCHES EXPECTED FOR SOME AREAS. 
LOCALIZED FLASH FLOODING WILL BE POSSIBLE.

DISCUSSION...A LARGE UPPER LEVEL LOW CURRENTLY OVER NORTHERN
MEXICO IS SLOWLY MAKING ITS WAY TOWARDS SOUTHERN TEXAS THIS
MORNING.  LARGE SCALE UPPER LEVEL DIVERGENCE AHEAD OF THIS FEATURE
IS RESULTING IN VIGOROUS ASCENT OVER DEEP SOUTH TEXAS AND
EXTENDING NORTHWARD ALONG THE COAST TOWARD THE GREATER HOUSTON
AREA OVERNIGHT.  A POOL OF 2 INCH PWS IS JUST OFFSHORE AND THE
LATEST RAP MODEL GUIDANCE SUGGEST PWS NEAR 1.75 INCHES IS LIKELY
NEAR THE COAST ALONG WITH 30 KTS OF 850MB SOUTHEASTERLY INFLOW. 
GIVEN THAT THE SURFACE FRONT IS OFFSHORE, THE CONVECTION THAT
DEVELOPS WILL BE ELEVATED.  

ANTECEDENT RAINFALL OVER THE PAST 36 HOURS IS AN AGGRAVATING
FACTOR IN INCREASING THE FLOODING POTENTIAL OVER THIS REGION, WITH
THE LOWEST FLASH FLOOD GUIDANCE VALUES JUST WEST OF THE GREATER
CORPUS CHRISTI AREA.  THE LATEST WRF MODEL GUIDANCE IS INDICATING
RAINFALL AMOUNTS ON THE ORDER OF 2 TO 4 INCHES POSSIBLE THROUGH
12Z, WITH SIMILAR AMOUNTS DEPICTED BY THE NAM CONEST.  THE HRRR IS
MORE CONSERVATIVE WITH ITS AMOUNTS ON THE ORDER OF 1 TO 2 INCHES. 
OVERALL, THIS IS A MARGINAL CASE FOR FLASH FLOODING, AND LOCALIZED
FLOODING IS THE MAIN CONCERN.

HAMRICK

ATTN...WFO...BRO...CRP...EWX...HGX...

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

LAT...LON   30339525 29609454 29079506 28449622 27859693 
            27299731 27059762 27089821 27239850 27679872 
            28389858 29369779 30109653