MESOSCALE PRECIPITATION DISCUSSION 0336
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1215 PM EDT WED JUN 20 2018

AREAS AFFECTED...SOUTHEAST TEXAS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 201615Z - 202115Z

SUMMARY...TRAINING BAND AND SLOW MOVING CELLS ALONG TROUGH AXIS
POSE POSSIBLE FLASH FLOODING RISK OVER NEXT FEW HOURS.

DISCUSSION...RADAR MOSAIC SHOWS A SHARPENING MCV OVER OVER N BEE/N
LIVE OAK COUNTY WITH N-S ORIENTED OUTLFOW BAND FROM LAVACA TO
CALHOUN INTO THE WESTERN GULF.  THE MCV REMAINS CONNECTED TO THE
MID-LEVEL TROF EXITING TO THE NORTHEAST AND IS CURRENTLY ORIENTED
BETWEEN LEE TO HOUSTON TO HARRISON COUNTY.  SOUTH AND EAST OF
THESE BOUNDARIES...CLEAR SKIES AND GULF ENVIRONMENT SUPPORTS
WARM/MOIST AND UNSTABLE ENVIRONMENT WITH MLCAPES TO 1000-1500 NEAR
GALVESTON BAY.  HOWEVER CLOUD COVER NEAR THE SLOWLY EASTWARD
PROGRESSING LINE HAS REDUCED TEMPS AND THEREFORE INSTABILITY TO NO
MORE THAN 500 J/KG.  THE MCV HAS SUPPORTED SOME LOW LEVEL BACKING
TO INCREASE LOW LEVEL CONVERGENCE AND ADVECTION OF THIS MODERATELY
UNSTABLE AIR INTO THE N-S TRAINING BAND.  AS SUCH RATES ARE STEADY
AROUND 1"/HR CURRENTLY BUT OFFSHORE INCREASING VERTICAL DEPTH (PER
OVERSHOOTING TOPS IN 1 MINUTE MESO VISIBLE IMAGERY) SUGGEST
INCREASING THREAT OF 2"+/HR CELLS MAY BE ON THE WAY BUT LIKELY
LIMITED TO THE COASTAL COUNTIES.  SO 2-3" IS POSSIBLE ALONG THIS
BAND AND NEW FLASH FLOODING IS CONSIDERED POSSIBLE IN THE NEXT FEW
HOURS

LOW LEVEL FLOW OFF THE GULF AT 15-20KTS IS STARTING TO PILE UP AT
WEAK SFC CONVERGENCE LINE COINSIDENT WITH THE MID-LEVEL TROF NEAR
GYB TO CLL TO LFK.  HI-RES CAMS ARE SUGGESTIVE OF SOME INCREASED
ISENTROPIC ASCENT IN THIS PROXIMITY THAT WOULD BUILD SLOWLY
SOUTHWARD INTO THE STRENGTHENING AND MORE UNSTABLE INFLOW
ENVIORNMENT.  RATES OF 1.5-2"/HR ARE POSSIBLE BUT LIKELY MORE
LIMITED IN TIME/DURATION WITH SURGES IN THE INFLOW ENVIRONMENT. 
THIS AREA IS ALSO GENERALLY BEEN DRY BUT IF THE CONVECTION COULD
BUILD SOUTHWARD TOWARD WALLER/AUSTIN AND S GRIMES THAT WERE AFFECT
YESTERDAY...FLASH FLOODING WOULD BE MORE LIKELY.  HOWEVER IT IS
MORE LIKELY TO BE IN THE LEE TO HOUSTON COUNTY TRACK OR EVEN
FURTHER NORTH...SO FLASH FLOODING IS CONSIDERED POSSIBLE AT THIS
TIME.

GALLINA

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

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

LAT...LON   31109563 30889519 29939555 28569603 28219653
            28019702 29139713 30249718 30699644