MESOSCALE PRECIPITATION DISCUSSION 0475
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
649 PM EDT WED JUL 12 2017

AREAS AFFECTED...GOLD COAST AND UPPER KEYS OF FL

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

VALID 122248Z - 130303Z

SUMMARY...THUNDERSTORMS WITH HIGH RAIN RATES MOVING INTO THE
WESTERN SUBURBS OF THE GOLD COAST.  HOURLY RAIN RATES UP TO 3"
WITH LOCAL AMOUNTS UP TO 5" ARE POSSIBLE.

DISCUSSION...THE COMBINATION OF A WESTWARD-MOVING
TROPICAL/EASTERLY WAVE ASSOCIATED WITH THE REMAINS OF TROPICAL
DEPRESSION FOUR AND AN EASTWARD MOVING OUTFLOW BOUNDARY FROM THE
EVERGLADES ARE LEADING TO HEAVY RAINFALL MOVING INTO THE WESTERN
SUBURBS OF MIAMI-DADE AND BROWARD COUNTIES.  EXPERIMENTAL GOES-16
IMAGERY SHOWS A BAND POSSIBLY INDUCED BY FRICTIONAL CONVERGENCE
ALONG THE SOUTHERN BAHAMAS HEADING TOWARDS THE NORTHERN KEYS. 
RADAR IMAGERY SHOWS A SIMILAR BAND MOVING OFF OF GRAND BAHAMA
ISLAND INTO EAST-CENTRAL FL/THE TREASURE COAST.  PRECIPITABLE
WATER VALUES ARE ~2.25" AND MLCAPE VALUES ARE ~3000 J/KG.  INFLOW
AT 850 HPA IS 15-20 KTS (5-10 KNOTS GREATER THAN THE MEAN 850-400
HPA WIND) AND SOMEWHAT CONVERGENT OUT OF THE EAST-SOUTHEAST.

THE EASTWARD DRIFT OF THE OUTFLOW BOUNDARY SHOULD CONTINUE MOVING
INTO/THROUGH THE GOLD COAST OVER THE NEXT SEVERAL HOURS WHILE THE
CONVERGENCE BAND MOVES TOWARDS THE KEYS IN THE WAKE OF THE
TROPICAL/EASTERLY WAVE.  RECENT RAP RUNS INDICATE A SLIGHT
INCREASE IN THE 850 HPA INFLOW IS POSSIBLE OVER THE NEXT SEVERAL
HOURS, WHICH COULD AID THE BACKBUILDING WHICH HAS BEEN OCCURRING
ALONG THE GOLD COAST.  CONSIDERING THE MOISTURE AND INSTABILITY
AVAILABLE, HOURLY RAIN RATES UP TO 3" WITH LOCAL AMOUNTS UP TO 5"
ARE POSSIBLE, WHICH ASSUMES THAT THE OUTFLOW BOUNDARY PUSHES INTO
THE GULF STREAM.  FORECAST UNCERTAINTY CAPPED THE HORIZON AT
AROUND FOUR HOURS.  MOST OF THE CONTENT WAS COORDINATED WITH THE
MFL/MIAMI FL FORECAST OFFICE.

ROTH

ATTN...WFO...KEY...MFL...MLB...

ATTN...RFC...SERFC...

LAT...LON   27678039 26818000 25748008 25028041 24788085
            25528061 25908051 26158043 26458061 26678043
            27528052