390
FXUS62 KKEY 280749
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
349 AM EDT MON SEP 28 2026
..NEW DISCUSSION, MARINE, AVIATION
KEY MESSAGES
- MODERATE TO MAJOR SALTWATER FLOODING OF LOW ELEVATION STREETS
AND LOTS IS LIKELY TO CONTINUE THROUGH THIS WEEK DUE TO KING
TIDE. DON'T DRIVE THROUGH FLOODED ROADWAYS. BOATERS CAN EXPECT
LESS CLEARANCE UNDER FIXED BRIDGES.
- A COASTAL FLOOD ADVISORY IS IN EFFECT FOR THE LOWER TO MIDDLE
KEYS, AND A COASTAL FLOOD WARNING IS IN EFFECT FOR THE UPPER
KEYS.
- MOISTURE WILL BEGIN FILTERING INTO THE AREA STARTING TODAY AND
CONTINUING THROUGH THE END OF THE WEEK. THIS WILL PROMOTE ABOVE
NORMAL RAIN AND THUNDER CHANCES, ESPECIALLY TUESDAY AND ONWARD
DISCUSSION
ISSUED AT 320 AM EDT MON SEP 28 2026
IT HAS BEEN A QUIET OVERNIGHT ACROSS THE KEYS AND SURROUNDING
COASTAL WATERS. HOWEVER, NOT TOO FAR AWAY WE HAVE BEEN OBSERVING
SHOWERS AND THUNDERSTORMS DEVELOPING FROM AROUND THE ISLE OF YOUTH
(SOUTH OF CUBA), NORTHWEST TOWARDS ANDROS ISLAND. THIS ACTIVITY IS
DEVELOPING AND MOVING NORTHEAST THANKS TO A RATHER DEEP EARLY
SEASON TROUGH THAT IS DIGGING ACROSS THE GULF WATERS AND INTO THE
YUCATAN CHANNEL. AT THE SURFACE WE CONTINUE TO SEE WEST TO
NORTHWEST WINDS AT NEARLY ALL OF OUR OBSERVATION PLATFORMS. A WEAK
FRONTAL BOUNDARY CAN BARELY BE MADE OUT ON RADAR AS IT LIES
ACROSS THE DISTANT STRAITS OF FLORIDA.
THIS FRONTAL BOUNDARY AND THE AFOREMENTIONED TROUGH IS CAUSING
QUITE THE HEADACHE THIS MORNING WITH THE GOING FORECAST. SATELLITE
DERIVED VORTICITY ANALYSIS SHOWS NO REAL INDICATIONS OF A
SHORTWAVE PRESENT EXCEPT AT THE 850 MB LEVEL. THIS VORT MAX IS
DEVELOPING AT THE BASE OF THE TROUGH AND WE CAN SEE THAT IT'S BEEN
ENOUGH TO FIRE OFF THE SHOWERS AND THUNDERSTORMS AS PREVIOUSLY
DESCRIBED. HOWEVER, MODELS ARE NOT ENTHUSIASTIC OF ADDITIONAL
SHORTWAVES DEVELOPING AND EJECTING OUT OF THIS TROUGH TODAY.
MEANWHILE, THE FRONTAL BOUNDARY NOTED ACROSS THE STRAITS WILL
SLOWLY LIFT NORTHWARD TODAY. THIS WOULD PUT THE KEYS IN A
SOUTHWEST FLOW BY THE AFTERNOON. THIS WIND DIRECTION WOULD TEND TO
FAVOR A REVERSE CLOUDLINE POTENTIALLY DEVELOPING. IT WILL COME
DOWN TO HOW MUCH OVERHEAD CIRRUS WE GET TODAY. WE COULD HAVE
ENOUGH OF A CIRRUS SHIELD FROM THE NEARBY TROUGH TO INHIBIT MUCH
GROWTH IF A CLOUDLINE TRIES TO DEVELOP.
AS SUCH, MADE THE DIFFICULT DECISION TO LOWER POPS SLIGHTLY FOR
TODAY. TIME WILL TELL IF THE RIGHT DECISION WAS MADE. REGARDLESS,
AS WE GO INTO TONIGHT AND INTO TUESDAY, MOISTURE WILL ONLY BE
INCREASING WHILE THE TROUGH BEGINS SHARPENING ACROSS THE GULF
BASIN. THIS WILL LEAD TO MUCH BETTER CONVERGENCE AND CONFLUENCE OF
BOTH MOISTURE AND MASS FOR MUCH OF THIS WEEK. THEREFORE, STILL
FEEL FAIRLY CONFIDENT AT ABOVE NORMAL RAIN/THUNDER CHANCES FOR THE
REMAINDER OF THE PERIOD. THIS ACTIVE, WET PERIOD MAY ALSO BE
PROBLEMATIC AS A NOR'EASTER HAS BEEN PARKED NORTH OF THE
GULFSTREAM AND THE SWELLS GENERATED BY THIS SYSTEM IS GOING TO
BACK UP THE GULFSTREAM OVER THE COMING DAYS. MODERATE TO MAJOR
SALTWATER FLOODING IS LIKELY TO CONTINUE.
MARINE
ISSUED AT 320 AM EDT MON SEP 28 2026
COASTAL FLOODING IS EXPECTED TO CONTINUE THROUGH THE NEXT SEVERAL
DAYS. THIS WILL LEAD TO LESS CLEARANCE UNDER FIXED BRIDGES AS WELL
AS SOME SEAWALLS AND DOCKS BECOMING OVERTOPPED. ALTHOUGH WE ARE
PAST THE FULL MOON, A POWERFUL NOR'EASTER WILL BE BACKING UP THE
GULFSTREAM THIS WEEK AND MAINTAINING COASTAL FLOODING THROUGH THE
NEXT SEVERAL DAYS. MEANWHILE, A HIGH PRESSURE WILL MOVE EAST AND
REACH THE EASTERN SEABOARD ON TUESDAY, THEN MOVE OFFSHORE AND
MERGE WITH A HIGH PRESSURE ACROSS THE WESTERN NORTH ATLANTIC. THIS
WILL ALLOW THE NEWLY MERGED FEATURE TO BUILD SOUTHWARD, LEADING TO
FRESHENING EASTERLY BREEZES. CONFIDENCE IS GROWING THAT WE WILL
SEE A PERIOD OF MODERATE TO FRESH BREEZES, ESPECIALLY WEDNESDAY
NIGHT THROUGH FRIDAY.
AVIATION
(06Z TAFS)
ISSUED AT 320 AM EDT MON SEP 28 2026
VFR CONDITIONS WILL GENERALLY BE EXPECTED. A REVERSE CLOUDLINE
MAY DEVELOP THIS AFTERNOON AS SURFACE WINDS GO SOUTHWEST. THIS
SETUP WOULD TEND TO FAVOR THE MTH TERMINAL AS OPPOSED TO THE EYW
TERMINAL. HOWEVER, A DEVELOPING UPPER LEVEL WEATHER SYSTEM WILL
LIE TO OUR WEST AND MAY EJECT OUT OCCASIONAL SHOWER AND
THUNDERSTORMS. CONFIDENCE IS TOO LOW TO INCLUDE MENTIONS OF
VCSH/TS AT THIS TIME.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 88 77 86 77 / 30 50 70 60
MARATHON 87 78 86 78 / 20 50 60 60
KEY WATCHES/WARNINGS/ADVISORIES
FL...COASTAL FLOOD WARNING FOR FLZ076.
COASTAL FLOOD ADVISORY FOR FLZ077-078.
GM...NONE.
PUBLIC/MARINE/FIRE...LIW
AVIATION/NOWCASTS....LIW
DATA ACQUISITION.....LIW/PV
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