773  
FXUS62 KMLB 221950  
AFDMLB  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MELBOURNE FL  
350 PM EDT SUN APR 22 2018  
   
DISCUSSION
 
 
CURRENT/TONIGHT...  
BANDS OF SHOWERS WITH EMBEDDED STRONGER STORMS HAVE INCREASED IN  
COVERAGE/INTENSITY OVER THE PAST COUPLE OF HOURS, ESPECIALLY  
ALONG/OFFSHORE THE TREASURE AND SPACE COASTS. EVEN A FEW ROTATING  
SUPERCELLS DEVELOPED OFFSHORE MARTIN COUNTY SINCE MID TO LATE  
MORNING. SHORT RANGE GUIDANCE FOCUSES LATE AFTERNOON AND EVENING  
ACTIVITY NEAR THE EAST COAST AND OVER THE ATLANTIC, WHICH LOOKS  
REASONABLE GIVEN CURRENT RADAR IMAGERY. SHOULD SEE A SLOW DECREASE  
IN COVERAGE LATE INTO THE OVERNIGHT AS ONSHORE FLOW STARTS TO VEER  
MORE TO THE SE (AND EVEN SSE ACROSS THE NORTH LATE) AND THE FLOW  
ALOFT REMAINS WEAKLY DIVERGENT. SULTRY MINS IN THE U60S-L70S ONCE  
AGAIN.  
 
MONDAY...DAWDLING MID-UPPER LEVEL LOW OVER THE MID-MS VALLEY WILL  
SLUGGISHLY MAKE ITS WAY EAST TOWARD THE TN/OH VALLEYS LATE IN THE  
DAY. ATTENDANT SURFACE TROUGH/VERY WEAK FRONT WILL MOVE ACROSS THE  
AREA THROUGH THE AFTERNOON AND EARLY EVENING. GIVEN THE NORTHWARD  
ADVECTION OF VERY HIGH PWAT AIR AHEAD OF IT, COUPLED WITH A MODEST  
INCREASE IN UPPER DIVERGENCE AND PERHAPS A DIFFUSE ATTEMPT AT A  
WCSB, FULLY EXPECT ANOTHER AFTERNOON WITH WIDESPREAD COVERAGE OF  
SHOWERS ALONG WITH SCATTERED TS. FREQUENT C/G LIGHTNING, LOCALLY  
GUSTY WINDS AND TORRENTIAL RAINFALL WILL ACCOMPANY THIS ACTIVITY.  
MAX TEMPS IN THE 80-85F RANGE  
 
00Z TUE - 12Z WED...  
REX-TYPE BLOCKING PATTERN EXTENDING FROM THE GREAT LAKES TO THE MID  
SOUTH WILL BREAK DOWN AS AN H85-H30 SHORT WAVE TROF OVER THE PAC NW  
PUSHES ACRS THE NRN TIER STATES AND SHUNTS THE ANTICYCLONE FROM THE  
GREAT LAKES TO THE NEW ENGLAND/MID ATLC COAST BY SUNSET MONDAY.  
SOUTHWARD, THE WELL DVLPD CYCLONE OF THE REX-BLOCK OVER THE MID  
SOUTH WILL CREEP SLOWLY EASTWARD INTO THE TN/OH RIVER VALLEYS BY  
DAYBREAK TUE, THEN WILL ACCELERATE TO THE MID ATLC/CAROLINA COAST BY  
DAYBREAK WED AS IT IS PICKED UP BY THE AFOREMENTIONED PAC SHORT WAVE  
TROF.  
 
SLOW EVOLUTION OF THE WX PATTERN WILL MAINTAIN A DEEP S/SWRLY FLOW  
PATTERN ACRS CENTRAL FL THRU SUNSET TUE. THESE WINDS WILL TAP AN  
AREA OF ENHANCED H100-H70 MOISTURE OVER THE NW CARIB, WHILE HIGH  
MOISTURE POOLING WITHIN THE WARM SECTOR OF THE CYCLONE OVER THE  
CENTRAL GOMEX WORKS ITS WAY EASTWARD. AHEAD OF THE FRONT, PWAT  
VALUES EXPECTED TO REMAIN BTWN 1.50"-1.75", WHILE A MID LVL THERMAL  
TROF DROPS H50 TEMPS TO ARND -13C. RESULTING MID LVL LAPSE RATES  
BCMG MODERATELY STEEP WITH READINGS BTWN 6.5-7.0C/KM. SCT-NMRS  
SHRAS/TSRAS UNTIL THE FRONT PASSES THRU TUE/TUE NIGHT. DAY 3  
CONVECTIVE OUTLOOK HAS CENTRAL FL UNDER GENERAL TSRAS, BUT  
STRONG/LCL SVR WX CANNOT BE RULED OUT.  
 
POST FRONTAL WINDS BCMG W/NW WITH PRECIP ENDING ALONG AND NORTH OF I-  
4 ARND SUNSET TUE, AND OVER THE TREASURE COAST/LAKE-O REGION BY  
DAYBREAK WED. STRONG PREFRONTAL WARM AIR ADVECTION AND MCLDY SKIES  
WILL KEEP MIN TEMPS TUE MRNG IN THE M/U60S, MAX TEMPS TUE AFTN  
GENERALLY IN THE M80S. MINIMAL COOL AIR ADVECTION WITH THE COLD  
FRONT TUE NIGHT...MIN TEMPS IN THE L/M60S.  
 
EXTENDED...(PREV DISC)  
POST FRONTAL DRYING THROUGH THE MIDDLE OF THE WEEK IN THE PRESENCE  
OF WEAK HIGH PRESSURE. NOT MUCH IN THE WAY OF COOLING EFFECTS...  
TEMPS GENERALLY NEAR AVG. LOOK FOR AN APPRECIABLE PERIOD OF OFFSHORE  
FLOWING WIND MID-LATE WEEK. MODELS SEEM TO SUGGEST A SERIES OF  
SUCCESSIVE (MOSTLY) DRY BOUNDARY PASSAGES AS REINFORCEMENT LATER IN  
THE PERIOD AS THE MID-UPPER PATTERN SHOWS SHORT-WAVE TROUGH MOVING  
THROUGH THE SOUTHEAST ON THU AND THEN A MORE SIGNIFICANT TROUGH SAT.  
HOWEVER, MOISTURE WILL BE LACKING FOR MENTIONING ANY RAIN CHANCES  
GREATER THAN 20 PERCENT, AT LEAST UNTIL GREATER CERTAINTY IS  
ACQUIRED.  
 

 
   
AVIATION
 
 
SCT/NMRS SHOWERS AND A FEW THUNDERSTORMS ARE ONGOING FROM KSUA-KDAB,  
AND WILL CONTINUE THROUGH THIS EVENING. THESE SHOWERS AND STORMS ARE  
PRODUCING IFR CONDITIONS WITH 1-2SM VSBYS AND BKN010-020 CIGS. AFTER  
23/00Z ISOLATED SHOWERS WILL STILL BE POSSIBLE ALONG THE COAST, THUS  
HAVE KEPT VCSH AT ALL COASTAL TERMINALS THROUGH THE END OF THE  
FORECAST PERIOD. THE LATEST VISIBLE SATELLITE IMAGERY SHOWS CLOUDS  
CLEARING ACROSS THE INTERIOR, THUS WILL KEEP VFR CONDITIONS FOR  
INTERIOR TERMINALS. HOWEVER, SOME SHOWERS AND STORMS CAPABLE OF  
PRODUCING IFR CONDITIONS ARE STILL POSSIBLE, SO I HAVE INCLUDED A  
TEMPO GROUP FOR KMCO-KSFB-KISM THROUGH 22/22Z.  
 

 
   
MARINE
 
 
TONIGHT-MONDAY...WAVE MODEL GUIDANCE SHOWS GOOD CONTINUITY WITH THE  
PREVIOUS FORECAST OF WINDS AND SEAS GRADUALLY VEERING TO SE LATE  
TONIGHT AND SOUTHERLY BY MONDAY AFTERNOON. WIND/SEAS GRADUALLY ABATE  
TO 15-20KT BY LATE TONIGHT, AND ABOUT 12-15KT MONDAY AFTERNOON AS  
THE SURFACE PRESSURE GRADIENT GRADUALLY LOOSENS. SCA CONDITIONS WILL  
EASE NEAR THE COAST BY LATE THIS EVENING, AND OFFSHORE BY MID  
MORNING MONDAY. SEAS 6-8FT EARLY TONIGHT, SUBSIDING TO 4-6FT MONDAY  
AFTERNOON.  
 
MON NIGHT...POOR BOATING CONDS BCMG MARGINAL BY DAYBREAK AS THE LCL  
PGRAD SLACKENS AHEAD OF AN APPROACHING COLD FRONT. MODERATE TO FRESH  
S/SE BREEZE BCMG GENTLE TO MODERATE WITH SEAS 3-5FT NEARSHORE AND 4-  
6FT OFFSHORE...SUBSIDING TO 3-4FT NEARSHORE AND 4-5FT OFFSHORE.  
DOMINANT PDS ARND 8SEC EXCEPT SOUTH OF FT. PIERCE INLET WHERE THE  
SHADOW OF GRAND BAHAMA ISLAND WILL KEEP PDS BTWN 5-6SEC. SHRAS  
LIKELY WITH A SLGT CHC OF TSRAS.  
 
TUE/TUE NIGHT...MARGINAL BOATING CONDS AS SFC/BNDRY LYR WINDS VEER  
TO SW AHEAD OF THE FRONT THRU THE DAY, THEN TO W/NW OVERNIGHT AS THE  
FRONT PRESSES THRU CENTRAL FL. SEAS SUBSIDING TO 2-4FT NEARSHORE AND  
3-5FT OFFSHORE, BUT WITH INCREASING SHORT PD CHOP AS THE ATLC WATERS  
BECOME FETCH PROTECTED. NMRS SHRA/CHC TSRAS TUE...ENDING FROM N TO S  
AFT SUNSET IN THE WAKE OF THE FRONT.  
 
WED-THU...POST-FRONTAL WESTERLIES WITH A LIGHT TO GENTLE BREEZE  
AREAWIDE, BCMG ONSHORE NEAR THE COAST EACH AFTN AS THE WEAK PGRAD  
AND STRONG SFC HEATING ON LAND PROMOTES THE FORMATION OF THE EAST  
COAST SEA BREEZE. SEAS 2-3FT NEARSHORE AND 3-4FT OFFSHORE THRU THU  
AFTN, SUBSIDING TO 2-3FT AREAWIDE THU NIGHT.  
 
FRI-FRI NIGHT...WEAK FRONTAL PASSAGE EARLY MRNG THRU LATE AFTN WILL  
HAVE MINIMAL IMPACT ON LCL SEAS. LIGHT TO GENTLE WESTERLY BREEZE,  
MEANDERING BTWN W/NW EARLY TO S/SW IN THE AFTN/EVNG, BEFORE  
SHIFTING BACK TO NW OVERNIGHT. SEAS 2-3FT AREAWIDE.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
DAB 68 80 67 83 / 70 80 30 60  
MCO 67 84 68 85 / 50 70 30 60  
MLB 70 82 68 84 / 70 80 50 70  
VRB 70 82 68 83 / 70 80 60 70  
LEE 68 84 68 84 / 50 60 30 60  
SFB 66 83 67 85 / 50 70 30 60  
ORL 68 84 68 85 / 50 70 30 60  
FPR 70 82 69 83 / 60 80 60 70  
 

 
   
MLB WATCHES/WARNINGS/ADVISORIES
 
 
FL...NONE.  
AM...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR FLAGLER  
BEACH TO VOLUSIA-BREVARD COUNTY LINE 0-20 NM-SEBASTIAN  
INLET TO JUPITER INLET 0-20 NM-VOLUSIA-BREVARD COUNTY LINE  
TO SEBASTIAN INLET 0-20 NM.  
 
SMALL CRAFT ADVISORY UNTIL 11 AM EDT MONDAY FOR FLAGLER BEACH TO  
VOLUSIA-BREVARD COUNTY LINE 20-60 NM-SEBASTIAN INLET TO  
JUPITER INLET 20-60 NM-VOLUSIA-BREVARD COUNTY LINE TO  
SEBASTIAN INLET 20-60 NM.  
 

 
 

 
 
SHORT TERM...CRISTALDI  
AVIATION.....RODRIGUEZ  
LONG TERM/IMPACT WX...BRAGAW/SMITH  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab FL Page Main Text Page