MESOSCALE PRECIPITATION DISCUSSION 0650
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
353 AM EST TUE NOV 17 2015
 
AREAS AFFECTED...SOUTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 170853Z - 171453Z
 
SUMMARY...THUNDERSTORMS ARE BEGINNING TO FORM AND SHOW SOME
TRAINING CHARACTER BETWEEN AUSTIN AND HOUSTON TX.  WITH HOURLY
RAIN RATES UP TO 2" POSSIBLE, FLASH FLOODING IS POSSIBLE.

DISCUSSION...AN AREA OF THUNDERSTORMS IS FORMING INSIDE THE MIDDLE
TX COAST, ASSOCIATED WITH A SLIGHTLY CONVERGENT AREA AT 850 HPA
AND A DIVERGENT AREA ALOFT NEAR THE SUBTROPICAL JET STREAM.  IT
ALSO LIES NEAR THE FRINGE OF THE 73F ISODROSOTHERM.  PRECIPITABLE
WATER VALUES OF 1.8-2.2" HAVE BEEN REPORTED RECENTLY VIA GPS. 
LOW-LEVEL INFLOW IS SIGNIFICANT, OUT OF THE SOUTH NEAR 50 KTS,
SLIGHTLY EXCEEDING THE MEAN 850-400 HPA WIND.  MUCAPES IN THE
REGION ARE 1000-2000 J/KG.  HOURLY RAIN RATES UP TO 1" HAVE BEEN
SHOWN VIA DUAL POL RADARS IN THE AREA.

THE 00Z ARW, 00Z NMMB, AND 00Z CANADIAN REGIONAL MODELS HAD THE
BEST IDEA CONCERNING THE EXISTENCE AND PLACEMENT OF THIS
CONVECTIVE AREA.  CURRENTLY, THE THUNDERSTORMS SHOW MINIMAL
ORGANIZATION AND ARE TRAVELING WITH THE MEAN WIND.  WITH TIME, THE
STORMS COULD ORGANIZE AND TURN MORE TO THE EAST-NORTHEAST.  THE
GUIDANCE THAT FORECAST THESE THUNDERSTORMS ADVERTISED LOCAL
AMOUNTS IN THE 2-4" RANGE, WHICH COULD FALL QUICKLY.  HOURLY RAIN
RATES UP TO 2" ARE POSSIBLE HERE, MAINLY DUE TO CELL TRAINING,
THOUGH TOWARDS THE END OF THE PERIOD, CELL MERGERS WITH THE
APPROACHING SQUALL LINE/COLD FRONT ARE POSSIBLE.  THE ADVERTISED
RAINFALL AMOUNTS WOULD CHALLENGE THREE HOUR FLASH FLOOD GUIDANCE
VALUES ACROSS THE REGION.  FLASH FLOODING IS CONSIDERED POSSIBLE,
PARTICULARLY WITHIN URBAN AREAS.

ROTH

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

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

LAT...LON   32679470 32519354 30679432 28819726 28699894 
            29859861 31889633