395  
AWUS01 KWNH 172250  
FFGMPD  
FLZ000-180400-  
 
MESOSCALE PRECIPITATION DISCUSSION 1178  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
550 PM EST TUE DEC 17 2024  
 
AREAS AFFECTED...EAST COAST OF FL  
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE  
 
VALID 172248Z - 180400Z  
 
SUMMARY...LOCALIZED FLASH/URBAN FLOODING WILL BE POSSIBLE ALONG  
THE EASTERN FL PENINSULA OVER THE NEXT FEW HOURS. SLOW CELL  
MOVEMENT AND/OR TRAINING WILL BE CAPABLE OF 1 TO 3 IN/HR RAINFALL  
RATES WHICH MAY GENERATE ISOLATED EXCESS RUNOFF WITHIN THE URBAN  
CORRIDOR.  
 
DISCUSSION...RADAR IMAGERY FROM KMLB AND INFRARED SATELLITE  
IMAGERY THROUGH 2230Z SHOWED SCATTERED THUNDERSTORMS OCCURRING  
ALONG THE EAST COAST OF FL BETWEEN CAPE CANAVERAL AND PORT SAINT  
LUCIE, STREAMING IN FROM THE EAST FOLLOWING THE MEAN LOW TO  
MID-LEVEL EASTERLY FLOW BETWEEN 10-20 KT. SURFACE DEWPOINTS IN THE  
LOWER 70S HAVE CONTRIBUTED TO ANOMALOUS MID-DECEMBER MOISTURE WITH  
PRECIPITABLE WATER VALUES BETWEEN 1.5 AND 1.8 INCHES (90TH  
PERCENTILE) WITH 1500-2000 J/KG MLCAPE OBSERVED ON THE 22Z SPC  
MESOANALYSIS.  
 
CELLS WERE LOCATED JUST NORTH OF A WEAK MID-UPPER LEVEL VORTICITY  
MAX OBSERVED ON WATER VAPOR IMAGERY OVER SOUTH-CENTRAL FL, ALONG A  
PERSISTENT WEST-EAST CONVERGENCE AXIS SEEN IN FADING VISIBLE  
IMAGERY OFFSHORE OF THE EAST COAST. MEAN EASTERLY WINDS IN THE LOW  
TO MID-LEVELS HAVE SUPPORTED REPEATING CELLS WITH SHORT-TERM  
TRAINING, WITH OBSERVED RAINFALL RATES OF 1-2 IN/HR NEAR VERO  
BEACH. WHILE RECENT CLOUD TOP COOLING ON SATELLITE IMAGERY HAS  
APPEARED TO MIGRATE GENERALLY JUST OFFSHORE, REDEVELOPMENT AND  
WESTWARD TRANSLATION OF HEAVY RAIN LOOKS TO CONTINUE A SHORT-TERM  
URBAN/FLASH FLOOD THREAT FROM SOUTHERN BREVARD COUNTY INTO ST.  
LUCIE COUNTY ALONG THE COAST WHERE AN ADDITIONAL 2-4 INCHES WILL  
BE POSSIBLE ON A HIGHLY LOCALIZED BASIS THROUGH ~01Z.  
 
INDICATIONS ARE THAT THESE CELLS WILL WEAKEN AFTER 00Z AS BOUNDARY  
LAYER STABILIZATION OCCURS WITH NOCTURNAL COOLING, WITH CELLS  
SHIFTING MORE OFFSHORE OR PERHAPS DISSIPATING. WHILE THE HRRR  
HASN'T BEEN DOING WELL WITH THE ONGOING PLACEMENT OF CELLS, THERE  
ARE INDICATIONS IN RECENT HRRR GUIDANCE THAT THE ACTIVITY COULD  
REFOCUS A BIT FARTHER SOUTH SOMETIME IN THE 00-03Z TIME FRAME.  
SIMILAR POTENTIAL FOR SLOW MOVEMENT AND/OR TRAINING WILL EXIST IS  
DEVELOPMENT DOES GET GOING FARTHER SOUTH LATER TONIGHT. ANY AREAS  
OF FLASH FLOODING ARE EXPECTED TO REMAIN LOCALIZED WITH POTENTIAL  
FOR A QUICK 2-4 INCHES OVER THE NEXT FEW HOURS.  
 
OTTO  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT  
 
ATTN...WFO...MFL...MLB...  
 
ATTN...RFC...SERFC...NWC...  
 
LAT...LON 28308046 27768008 26657985 26118002 26178029  
26258043 26628045 27058049 27558065 28018077  
 
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