MESOSCALE PRECIPITATION DISCUSSION 0030
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EDT THU MAY 02 2013
 
AREAS AFFECTED...SOUTHERN FL INCLUDING THE KEYS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 021730Z - 022230Z
 
SUMMARY...MERGING AREAS OF CONVECTION FROM THE EAST COAST SEA
BREEZE AND SLOW-MOVING ORGANIZED CONVECTION MOVING IN FROM THE
GULF OF MEXICO SHOULD LEAD TO ADDITIONAL FLASH FLOODING THIS
AFTERNOON.

DISCUSSION...SLOW-MOVING CONVECTION, WITH A TAIL OF ACTIVITY
MOVING IN FROM THE SOUTHWEST -- FL STRAITS -- HAS BEEN TIED TO A
BOUNDARY AND POSSIBLE SURFACE LOW IN THE FLORIDA STRAITS. THIS
ACTIVITY HAS BROUGHT RAINFALL RATES AVERAGING TWO INCHES PER HOUR
PER RADAR ESTIMATES, WITH LOCAL RATES UP TO SIX INCHES, WITHIN
THREE HOURS' TIME, THOUGH SOME EMBEDDED HAIL MIGHT BE INFLATING
RAINFALL ESTIMATES.  THE AREA IS MOVING INLAND INTO SOUTHWESTERN
FL AND THROUGH THE KEYS AT THIS TIME -- WITH THE KEYS RECENTLY
REPORTING FLASH FLOODING.  MOISTURE IS PLENTIFUL, WITH
PRECIPITABLE WATER VALUES (PWS) APPROACHING TWO INCHES ACROSS THE
REGION.  THE REGION SHOWS SIGNIFICANT DIVERGENCE ALOFT AHEAD OF AN
UPPER LEVEL SHEAR LINE MOVING INTO THE STATE.  ADD INTO THE MIX
NON-MOVING SEA BREEZE CONVECTION ALONG THE GOLD COAST -- WHICH HAS
ALSO LED TO LOCALIZED FLASH FLOODING --- WHICH SHOULD MERGE IN
WITH THE INVADING ACTIVITY FROM SOUTHWESTERN FL, AND FLASH
FLOODING IS EXPECTED ACROSS THE REGION THROUGH THE AFTERNOON
HOURS.  FLASH FLOOD GUIDANCE (FFGS) ARE LOWER THAN YESTERDAY IN
THE WAKE OF YESTERDAY'S WIDESPREAD CONVECTION, ON THE ORDER OF
THREE INCHES IN THREE HOURS' TIME, WHILE THE KEYS HAVE VALUES
CLOSER TO TWO INCHES IN THREE HOURS' TIME.  WITH THE RECENT RADAR
RATES AND FFGS IN MIND, OUTLINED THE SOUTHERN PENINSULA SOUTH OF
LAKE OKEECHOBEE AND THE FLORIDA KEYS FOR ADDITIONAL FLASH
FLOODING. 

ROTH


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

LAT...LON   25778206 26908103 27368002 26617981 25248020 24528114
            24498241 25778206