MESOSCALE PRECIPITATION DISCUSSION 0092
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
348 PM EDT FRI MAR 25 2016
 
AREAS AFFECTED...PORTIONS OF SOUTHERN/CENTRAL FL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251947Z - 260147Z
 
SUMMARY...CONVECTION IS GROWING WITHIN A MOIST ENVIRONMENT WITH
INCREASING INSTABILITY.  HOURLY RAIN RATES UP TO 2.5" COULD LEAD
TO FLASH FLOODING.

DISCUSSION...SATELLITE TRENDS SHOW CONVECTION WHICH HAS BACK BUILT
FROM NORTHWEST OF GRAND BAHAMA ISLAND INTO PORTIONS OF PALM BEACH
AND MARTIN COUNTIES.  A RECENT SATELLITE BRIEFING FROM SAB/NESDIS
INDICATES SHORTWAVES UPSTREAM THAT COULD BE PROVIDING A BOOST TO
THE RECENT CONVECTIVE DEVELOPMENT.  PRECIPITABLE WATER VALUES IN
THE REGION ARE HIGH, 1.75-2", WHICH IS 1.5-2 SIGMAS ABOVE THE MEAN
FOR LATE MARCH.  WINDS ALOFT ARE A BIT STRONGER THAN NORMAL AS THE
REGION LIES IN A DIVERGENT AREA BETWEEN THE SOUTHERN STREAM OF THE
POLAR JET AND THE SUBTROPICAL JET.  MLCAPES HAVE BEEN INCREASING,
WITH 2000-3000 J/KG ACROSS SOUTHERN FL SOUTH OF AN APPARENT WARM
FRONT.  LOW-LEVEL INFLOW IS ~20 KTS OUT OF THE WEST-SOUTHWEST PER
VAD WIND PROFILES, WELL ABOVE RAP FORECASTS FOR THE GOLD COAST. 
COMBINED WITH THE AVAILABLE INSTABILITY, THIS COULD LEAD TO
ORGANIZED THUNDERSTORMS WITH HIGH RAIN RATES.

THE 12Z SPCWRF, 12Z NAM CONEST, AND 12Z CANADIAN REGIONAL MODELS
APPEAR TO HAVE THE BEST HANDLE ON THE DEVELOPING CONVECTION,
THOUGH THEY COULD BE TOO FAR TO THE NORTH BASED ON WHERE SURFACE
BOUNDARIES ARE CURRENTLY LOCATED.  CONVECTION SHOULD FOCUS INLAND
OF THE WEST COAST NEAR THE LEADING EDGE OF THE WEST COAST SEA
BREEZE FRONT AND PROPAGATE EASTWARD AT ~35 KTS PER FORWARD
PROPAGATING CONVECTIVE VECTORS.  BACKBUILDING/TRAINING AND
POSSIBLE CELL MERGERS  COULD ALL CONTRIBUTE TO THE HEAVY RAINFALL
RISK.  LOCAL AMOUNTS OF 3-5", WITH HOURLY RAIN RATES UP TO 2.5",
ARE POSSIBLE IN THESE STORMS, WHICH WOULD FLIRT WITH THE THREE
HOUR FLASH FLOOD GUIDANCE VALUES AS WELL AS THE THREE HOUR 10 YEAR
RECURRENCE INTERVAL.  FLASH FLOODING IS CONSIDERED POSSIBLE,
PARTICULARLY WITHIN URBAN AREAS.  CONVECTIVE COVERAGE COULD BE
LESS THAN NORMALLY SEEN IN AN MPD AREA.

ROTH

ATTN...WFO...MFL...MLB...TBW...

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

LAT...LON   28468076 28238048 27508018 26927998 26778061 
            26808131 27548167 27818160