MESOSCALE PRECIPITATION DISCUSSION 0702
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 PM EDT SUN SEP 25 2016
 
AREAS AFFECTED...HILL COUNTY OF CENTRAL AND SOUTHWEST TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251730Z - 252100Z
 
SUMMARY...MATURE MCV SHIFTING EAST. AREAL COVERAGE OF HIGH
RAINFALL RATES REDUCING YET ISOLATED FLASH FLOOD THREAT REMAINS
FOR THE NEXT FEW HOURS. 

DISCUSSION...REGIONAL WSR-88D SHOW OCCLUDED MCV/MESO LOW WITH
WESTERLY WIND BURST SURGING SQUALL LINE MESO-COLD FRONT EASTWARD
NEARING OUTSKIRTS OF SAN ANTONIO IN THE NEXT HOUR OR SO.  VISIBLE
IMAGERY INDICATES NUMEROUS SE TO NW FEEDER CU BANDS THAT HAVE
SCATTERED TCU DEVELOPING CBS...LIKELY ON INCREASED CONVERGENCE
FROM SLIGHT VEERING LOW LEVEL FLOW THAT HAS BEEN SEEN IN VWP AND
PROJECTED FORWARD IN TIME BY THE RAP FORECAST FIELDS. WHERE CU
BANDS INTERSECT WITH E-W OUTFLOW BOUNDARY FROM LAST NIGHT'S
CONVECTION...REPEAT UPSTREAM DEVELOPMENT/BACK BUILDING MAY KEEP
WEAKER CORE CELLS ANCHORED FOR A QUICK BURST OF .5-1" TOTALS
PRECURSORY TO MAIN SQUALL LINE.  DEEP MOISTURE PROFILES WITH TPWS
IN THE 2" RANGE ALONG WITH SOME UNTAPPED MLCAPES TO 500-1000 J/KG
AND SUSTAINED MST FLUX FROM THESE FEEDER BANDS ARE LIKELY TO
MAINTAIN DEEP CONVECTION WITH RATES OVER 2"/HR ALONG THE
INTERSECTION OF THE SQUALL LINE/OLD OUTFLOW BOUNDARY OVER
HILLY/RUGGED TERRAIN POSING LOW END FLASH FLOOD THREAT GIVEN THE
DRIER SOIL CONDITIONS AND THE LIKELY CONTINUED QUICK EASTWARD
PROGRESSION OF THE MCV.  

LARGER SCALE BROAD DIFFLUENCE FROM RETROGRADING/CUTTING OFF UPPER
LOW ALONG WITH BROAD PVA FROM SHORTWAVE LIFTING THROUGH NORTHERN
MEXICO CONTINUES TO PROVIDE STRONG ASCENT NORTHWEST OF THE MCV
WITH A LARGE BROAD MDT-HVY PRECIPITATION SHIELD LIKELY TO BE
MAINTAINED.  GIVEN SUB 1" 1HR FFG VALUES ACROSS THE EDWARDS
PLATEAU...CONTINUED FLOODING REMAINS POSSIBLE HERE AS WELL.

GALLINA

ATTN...WFO...EWX...SJT...

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

LAT...LON   31199916 30439892 30349801 29809804 29389888 
            29139965 29000032 29810034 30430082 30980065