720  
FXUS62 KMFL 190554  
AFDMFL  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MIAMI FL  
154 AM EDT TUE MAR 19 2019  
   
AVIATION
 
 
PREVAILING MVFR CIGS ACROSS MOST TERMINALS WITH POSSIBLE IFR CIGS  
DEVELOPING BETWEEN 09-12Z TUESDAY MORNING DUE TO WIDESPREAD RAIN.  
CIGS MAY DROP TO AROUND 008 AGL AROUND THIS TIME. ALSO LOOKING  
FOR REDUCED VIS IN HEAVIER ROUNDS OF SHOWERS AND RAIN. RAIN ACTIVITY  
LOOKS TO SIMMER DOWN OVERNIGHT TUESDAY INTO WEDNESDAY MORNING,  
BUMPING CONDITIONS BACK TO VFR. OTHERWISE, BREEZY NNE TO NE WINDS  
WITH GUSTS IN THE 20-25 KT RANGE WILL PREVAIL THROUGHOUT THE DAY  
TODAY BEFORE QUIETING DOWN OVERNIGHT. THUNDERSTORMS ARE NOT  
MENTIONED AT THIS TIME DUE TO LOW CONFIDENCE.  
 

 
   
PREV DISCUSSION
 
/ISSUED 858 PM EDT MON MAR 18 2019/  
 
UPDATE...  
COASTAL CONVERGENCE AND ITS DEVELOPMENT OF LOCALLY HEAVY  
RAINSHOWERS IS THE MAIN CONCERN FOR TONIGHT. GUIDANCE CONTINUES TO  
SUGGEST A BAND WITHIN ABOUT 20 MILES OF THE ATLANTIC COAST SETTING  
UP WHERE SOME HEAVY RAINFALL WILL OCCUR. WHERE ALONG THE COAST THE  
ACTIVITY IS HEAVIEST AND WHETHER OR NOT THE LINE REMAINS OFFSHORE  
ARE TWO BIG UNCERTAINTIES, AND DETAILS OF THIS ARE STILL NOT ABLE  
TO BE REFINED AT THIS TIME. THE MORE WIDESPREAD LIGHT TO MODERATE  
RAIN ASSOCIATED WITH ISENTROPIC LIFT WILL LIKELY NOT START UNTIL  
TOWARD DAWN, BUT THE BANDING ALONG THE EAST COAST COULD INITIATE  
AS EARLY AS MIDNIGHT. HAVE ADJUSTED POPS DOWN FOR THE NEXT SEVERAL  
HOURS AS RADAR RETURNS ARE RELATIVELY SPARSE, OTHERWISE NO CHANGE  
IN THE OVERNIGHT FORECAST.  
 
PREV DISCUSSION... /ISSUED 416 PM EDT MON MAR 18 2019/  
 
DISCUSSION...  
 
SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)  
WITH THE COLD FRONT HAVING STALLED SOUTH OF THE REGION AND THE  
MUCH ADVERTISED SHORTWAVE TROUGH REMAINING OVER THE CENTRAL GULF  
TODAY, AN OVERCAST YET DRY DAY HAS ENSUED, WITH TEMPERATURES  
GETTING A BIT WARMER THAN ANTICIPATED WITH THE LACK OF RAINFALL.  
TEMPERATURES HAVE PEAKED IN THE MID 70S TO LOW 80S ACROSS THE  
REGION, DESPITE BEING ON THE COOL SIDE OF THE BOUNDARY. OVERALL  
SYNOPTIC SETUP REMAINS UNCHANGED FROM PREVIOUS FORECASTS. POTENT  
SHORTWAVE TROUGH AND SUBTROPICAL JET MAX WILL APPROACH THE REGION  
TONIGHT AND CROSS SOUTH FLORIDA ON TUESDAY. THIS ALONE WILL  
PROVIDE PLENTY OF ISENTROPIC LIFT TO SUPPORT WIDESPREAD MODERATE  
SHOWERS ACROSS THE REGION FROM LATE TONIGHT THROUGH TUESDAY  
AFTERNOON. SOME HEAVY RAIN IS POSSIBLE WITH THE AFOREMENTIONED  
FEATURES, BUT THE MOST LIKELY CULPRITS FOR HEAVY RAIN WILL LIKELY  
COME FROM TWO ADDITIONAL FEATURES. THE FIRST OF THESE FEATURES  
WILL BE MESOSCALE IN NATURE, THUS THERE IS INHERENT UNCERTAINTY IN  
TIMING AND LOCATION OF THE HEAVY RAIN POTENTIAL. COASTAL  
CONVERGENCE MAY SET UP OVERNIGHT IN THE VICINITY OF THE THE  
ATLANTIC COAST, AS MARINE FLOW TURNS MORE NORTHEASTERLY AND  
ENHANCES, WHILE LAND FLOW CONTINUES WITH A COOL ADVECTION/NORTH-  
NORTHWEST REGIME. WITH PWATS APPROACHING 2 INCHES, THIS ZONE OF  
CONVERGENCE COULD SUPPORT LOCALLY QUITE HEAVY RAINFALL, AND  
VARIOUS MODELS HAVE 4-6 INCH BULLSEYES OF PRECIPITATION FORECAST  
OVERNIGHT ALONG THE EAST COAST, OR ADJACENT WATERS. THIS SHOULD  
MAINLY OCCUR AFTER 6Z, AND IF THIS ZONE SETS UP OVER THE WATERS,  
SIGNIFICANT RAINFALL COULD REMAIN OVER THE ATLANTIC AND NOT IMPACT  
THE REGION. STILL, WPC HAS HIGHLIGHT THE EAST COAST URBAN AREAS IN  
A MARGINAL RISK FOR EXCESSIVE RAINFALL/FLOODING. MESOSCALE TRENDS  
WILL BE CLOSELY MONITORED OVERNIGHT.  
 
THE SECOND FEATURE THAT COULD LEAD TO HEAVY RAINFALL IS THE  
SURFACE LOW THAT IS EXPECTED TO FORM ALONG THE NEARLY STATIONARY  
BOUNDARY OVER THE KEYS IN RESPONSE TO THE SHORTWAVE TROUGH. THE  
LOW TRACK IS FORECAST TO REMAIN SOUTH OF THE REGION, BUT IF IT  
COMES CLOSE ENOUGH, MORE WIDESPREAD HEAVIER SHOWERS MAY IMPACT  
SOUTHEASTERN PARTS OF THE AREA. THIS POSSIBLE SCENARIO COULD LEAD  
TO A FEW ELEVATED THUNDERSTORMS AS WELL.  
 
REGARDLESS OF WHETHER OR NOT EITHER HEAVY RAIN SCENARIO HOLDS  
TRUE, THE WIDESPREAD ISENTROPIC LIFT INDUCED RAINFALL SHOULD  
PRODUCE 1 TO 3 INCHES ACROSS THE REGION BY TUESDAY NIGHT.  
TEMPERATURES TUESDAY WILL BE COOL DUE TO THE WIDESPREAD RAINFALL,  
WITH SOME AREAS LIKELY NOT REACHING 70 DEGREES. UPPER LEVEL  
SUPPORT AND MOISTURE SCOUR AWAY ON WEDNESDAY, BUT LOW-LEVEL  
MOISTURE AND NORTHEAST FLOW WILL PREVAIL, POTENTIALLY KEEPING  
SCATTERED TO NUMEROUS SHOWERS ONGOING ALONG THE ATLANTIC COAST.  
TEMPERATURES WILL REBOUND SOMEWHAT, BUT STILL BE A BIT BELOW  
NORMAL FOR WEDNESDAY AND WEDNESDAY NIGHT. MAXIMA WILL MAINLY BE IN  
THE 70S WITH MINIMA IN THE 50S INTERIOR, LOW TO MID 60S ACROSS THE  
EAST COAST URBAN AREAS.  
 
LONG TERM (THURSDAY THROUGH SUNDAY)  
RAIN CHANCES DECREASE ON THURSDAY AND FOR THE REMAINDER OF THE  
FORECAST PERIOD AS A ANOTHER WEAK, DRY FRONTAL PASSAGE HELPS TO  
CLEAR OUT THE DEEPER MOISTURE WELL TO OUR SOUTH. RAINFALL WILL  
REMAIN MOSTLY ALONG THE ATLANTIC AND EAST COAST UNTIL THE FRONT  
CLEARS. THEREAFTER, HIGH PRESSURE RETURNS, ALLOWING COOLER AND  
DRIER AIR TO FILTER IN ACROSS THE PENINSULA.  
 
MARINE...  
HAZARDOUS BOATING CONDITIONS ARE DEVELOPING THIS AFTERNOON ACROSS  
GULF AND ATLANTIC WATERS, AS NORTHERLY WIND WILL INCREASE TO 20 TO  
30 KNOTS OVERNIGHT AND REMAIN AT SIMILAR SPEEDS TUESDAY AND  
TUESDAY NIGHT (WHILE VEERING NORTHEASTERLY). SEAS IN GULF WATERS  
WILL BUILD TO 6 TO 8 FEET, WITH ATLANTIC SEAS INCREASING TO 8 TO  
10 FEET, HIGHER IN THE GULF STREAM. A SMALL CRAFT ADVISORY IS IN  
EFFECT FOR GULF WATERS INTO TUESDAY NIGHT AND FOR ATLANTIC WATERS  
THROUGH WEDNESDAY, AS HIGH SEAS MAY CONTINUE IN THE ATLANTIC  
THROUGH AT LEAST WEDNESDAY. WIDESPREAD RAIN IS EXPECTED INTO  
TUESDAY NIGHT, WITH ISOLATED THUNDERSTORMS ALONG WITH WATERSPOUTS  
POSSIBLE IN ATLANTIC WATERS DURING THIS TIME.  
 
BEACH FORECAST...  
 
DUE TO FORECAST NORTHEAST WIND OF 20 TO 30 MPH, THERE IS A HIGH  
RISK OF RIP CURRENTS ON ATLANTIC BEACHES FOR TUESDAY AND TUESDAY  
NIGHT. THIS HIGH RISK WILL LIKELY CONTINUE THROUGH AT LEAST  
THURSDAY.  
 
HYDROLOGY...  
WIDESPREAD RAINFALL AMOUNTS FROM LATE TONIGHT THROUGH TUESDAY  
NIGHT SHOULD AVERAGE 1 TO 2 INCHES ACROSS SOUTH FLORIDA, WITH 2 TO  
4 INCHES LIKELY ACROSS THE EAST COAST METROPOLITAN AREAS. AMOUNTS  
OF THIS MAGNITUDE SPREAD OVER 6 OR MORE HOURS SHOULD NOT CAUSE  
SIGNIFICANT FLOODING ISSUES BEYOND URBAN/STREET PONDING, AS  
ANTECEDENT CONDITIONS ARE QUITE DRY. HOWEVER, LOCALIZED MUCH  
HIGHER AMOUNTS ARE POSSIBLE, ESPECIALLY NEAR THE ATLANTIC COAST,  
ARE POSSIBLE, AND THESE AMOUNTS, IF THEY OCCUR WITHIN A FEW HOURS,  
MAY CAUSE FLOODING. WPC HAS PLACED THE EAST COAST URBAN AREAS IN  
A MARGINAL RISK OF EXCESSIVE RAINFALL/FLOODING FOR TONIGHT AND  
TUESDAY.  

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
WEST PALM BEACH 70 63 77 62 / 90 60 40 20  
FORT LAUDERDALE 71 65 78 65 / 90 60 40 20  
MIAMI 72 65 79 65 / 80 60 40 10  
NAPLES 70 60 79 59 / 80 50 10 0  
 

 
   
MFL WATCHES/WARNINGS/ADVISORIES
 
 
FL...HIGH RIP CURRENT RISK FROM 8 AM EDT THIS MORNING THROUGH  
WEDNESDAY MORNING FOR FLZ168-172-173.  
 
AM...SMALL CRAFT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR AMZ650-651-670-  
671.  
 
GM...SMALL CRAFT ADVISORY UNTIL 2 AM EDT WEDNESDAY FOR GMZ656-657-676.  
 

 
 
UPDATE...23/SBK  
DISCUSSION...23/SBK  
MARINE...23/SBK  
AVIATION...03/FELL  
BEACH FORECAST...23/SBK  
HYDROLOGY...23/SBK  
 
 
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