980
FXUS62 KKEY 291556
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1156 AM EDT TUE SEP 29 2026
..NEW UPDATE, AVIATION
KEY MESSAGES
- MODERATE TO MAJOR SALTWATER FLOODING OF LOW ELEVATION STREETS
AND LOTS IS LIKELY TO CONTINUE OVER THE NEXT FEW DAY OR SO DUE
TO KING TIDE. DON'T DRIVE THROUGH FLOODED ROADWAYS. BOATERS CAN
EXPECT LESS CLEARANCE UNDER FIXED BRIDGES.
- A COASTAL FLOOD WARNING IS IN EFFECT FOR THE UPPER KEYS,
PARTICULARLY ALONG THE SOUNDS, BAY SIDE OF KEY LARGO. A COASTAL
FLOOD ADVISORY IS IN EFFECT FOR THE MIDDLE AND LOWER KEYS.
- A WET PATTERN IS EXPECTED FOR THE NEXT SEVERAL DAYS ACROSS THE
KEYS. THIS WILL MAINTAIN ABOVE NORMAL RAIN AND THUNDER CHANCES
THROUGH AT LEAST THURSDAY.
UPDATE
ISSUED AT 1129 AM EDT TUE SEP 29 2026
DEEP TROPICAL MOISTURE CONTINUES TO SURGE INTO THE FLORIDA KEYS AS
UPPER AIR ANALYSIS SHOWS TROUGHING WITH A SLIGHT POSITIVE TILT
EXTENDING INTO THE YUCATAN REGION AND WESTERN CARIBBEAN AND A
MID/UPPER LEVEL ANTICYCLONE POSITIONED IN THE SUBTROPICAL ATLANTIC
SOUTHEAST OF BERMUDA. MEANWHILE, A 55-65 KT JET STREAK ANALYZED AT
250 MB IS STREAMING ACROSS THE FLORIDA PENINSULA, PROVIDING PLENTY
OF DIVERGENCE ALOFT ACROSS THE REGION AND THIS WILL GENERALLY
REMAIN IN PLACE THROUGH THE REMAINDER OF THE DAY AS THE UPPER
TROUGH AXIS REMAINS TO OUR WEST. GIVEN THE FAVORABLE FORCING FOR
ASCENT AND DEEP MOISTURE WITH PWATS AROUND 2 INCHES OR MORE,
ROUNDS OF SCATTERED TO OCCASIONAL NUMEROUS SHOWERS AND EMBEDDED
THUNDERSTORMS WILL DRIFT IN A GENERAL NORTHEASTWARD DIRECTION
ACROSS THE ISLAND CHAIN AND SURROUNDING COASTAL WATERS THE
REMAINDER OF THE DAY. THE 12Z KEY RAOB SHOWS GOOD MOISTURE IN THE
MID AND UPPER LEVELS WITH SOME DRY AIR AND INHIBITION IN THE LOW
LEVELS, LIKELY RELATED TO THE MORE STABLE AND POST-CONVECTIVE
ENVIRONMENT THAT WAS IN PLACE EARLIER. FORECAST SOUNDINGS THROUGH
THE REMAINDER OF THE DAY DO MAINTAIN SOMEWHAT DRIER AIR IN THE
LOWER LEVELS, WHICH MAY BE INDICATING SOME CUBAN SHADOW INFLUENCE
FROM LOW LEVEL SOUTHERLIES. HOWEVER, THE AFOREMENTIONED DYNAMICS
SHOULD BE ABLE TO OVERCOME THESE POTENTIAL LIMITING FACTORS
ENOUGH TO STILL SUPPORT LIKELY POPS SO WILL CONTINUE WITH THE
INHERITED FORECAST. WITH THIS OVERALL ENVIRONMENT OF DEEP MOISTURE
AND ASCENT, COUPLED WITH THE BACKGROUND OF ELEVATED TIDE LEVELS,
THE MAIN CONCERN WILL BE LOCALLY HEAVY RAINFALL AND FLOODING,
ESPECIALLY DURING HIGH TIDE CYCLES AND IN AREAS THAT TYPICALLY
EXPERIENCE KING TIDE FLOODING. OTHERWISE, DEWPOINTS HAVE RETURNED
TO THE MID 70S AREA-WIDE AND WITH HIGHS REACHING THE MID/UPPER 80S
LATER TODAY, THE MORE TYPICAL WARM AND HUMID FEEL TO THE AIR IN
LATE SEPTEMBER IS BACK AFTER THE RECENT MULTI-DAY SLIGHT TASTE OF
FALL.
DISCUSSION
ISSUED AT 436 AM EDT TUE SEP 29 2026
AN INCREDIBLY MESSY BUT DYNAMIC WEATHER PATTERN IS SETTING UP
ACROSS THE FLORIDA KEYS THIS MORNING. LET'S BREAK IT DOWN. AT THE
SURFACE WE HAVE WEAK RIDGING OCCURRING WHICH IS LEADING TO
CHAOTIC, BUT LIGHT SURFACE WINDS. IN THE LOWER LEVELS THE RIDGE
AXIS OF AN ATLANTIC RIDGE LIES JUST TO OUR SOUTH BUT IS STEADILY
MARCHING NORTHWARD. IN THE MID AND UPPER LEVELS WE HAVE A
PRONUNCED, DEEP TROUGH THAT EXTENDS FROM NEAR THE GREAT LAKES
REGION WELL SOUTH ACROSS THE GULF BASIN AND INTO THE WESTERN
CARIBBEAN. THIS FEATURE IS PROVIDING BROAD CYCLONIC FLOW ALOFT AS
WELL AS THE OCCASIONAL SHORTWAVE THAT HAS EJECTED NORTHEASTWARD.
THE AFOREMENTIONED ATLANTIC RIDGE AXIS WILL CONTINUE LIFTING
NORTHWARD TODAY. AS IT DOES, IT WILL HELP TO ALIGN OUR SURFACE
WINDS MORE OUT OF THE EAST TO SOUTHEAST. IN ADDITION, THE STEERING
FLOW MORE BECOME MORE SOUTHERLY, ALLOWING FOR BETTER MOISTURE
TRANSPORT FROM THE WESTERN CARIBBEAN AHEAD OF THE MID/UPPER LEVEL
TROUGH. THUS FAR THE TROUGH HAS RESIDED TO OUR WEST WITH A
PLETHORA OF CONVECTION ERUPTING THROUGHOUT THE LAST DAY OR SO.
HOWEVER, AS THIS ACTIVITY TRIES TO MOVE NORTHEAST AND AWAY FROM
THE TROUGH, IT HAS ENCOUNTERED MORE STABLE AND RELATIVELY DRIER
AIR. THIS HAS KEPT MUCH OF THE PRECIPITATION FROM REACHING THE
FLORIDA KEYS.
TODAY SHOULD BE THE TRANSITION POINT FOR THE KEYS. THE MID/UPPER
LEVEL TROUGH WILL SLOWLY EDGE EASTWARD TODAY ALLOWING FOR A BETTER
ALIGNMENT OF MOISTURE AND LIFT. THE FLY IN THE OINTMENT IS THE LOW
LEVEL RIDGE AXIS LIFTING NORTHWARD. THIS WILL CAUSE A SOUTHERLY
WIND BELOW 700 MB AND COULD BRING IN LOW LEVEL DRY, WARM AIR
ADVECTION. THIS MAY COUNTER THE INCREASING MOISTURE ALOFT, LEADING
TO AN OVERALL LOWER COVERAGE OF SHOWERS AND THUNDERSTORMS FOR
TODAY. HI-RES CAMS CONTINUE TO ADVERTISE THAT WE WILL HAVE ENOUGH
SYNOPTIC FORCING TO OVERCOME THE MORE MESOSCALE EFFECTS. TIME WILL
TELL IF THIS ACTUALLY HAPPENS.
ONCE THIS FEATURE SETS IN, WE CAN EXPECT MULTIPLE DAYS OF WET,
ACTIVE WEATHER THROUGH AT LEAST THURSDAY. THEREAFTER, A RIDGE OUT
ACROSS THE ATLANTIC WILL SHIFT FURTHER TO THE WEST AND RETROGRADE
THE MID/UPPER LEVEL TROUGH INTO THE BAY OF CAMPECHE. THIS WOULD
LOWER OUR RAIN CHANCES BACK CLOSER TO NORMAL WITH A MOIST EAST TO
SOUTHEAST FLOW.
MARINE
ISSUED AT 436 AM EDT TUE SEP 29 2026
A MUCH WETTER THAN NORMAL PATTERN IS IN PLACE ACROSS KEYS WATERS,
LASTING THROUGH THE NIGHT AND FOR AT LEAST THE NEXT SEVERAL DAYS.
AS RESULT, PERIODS OF POOR VISIBILITY, LOCALLY STRONG AND GUSTY
WINDS, AND THUNDERSTORMS CAN BE EXPECTED. ASIDE FROM CONVECTIVE
INFLUENCES, SURFACE WINDS WILL BE GENTLE OUT OF THE SOUTHWEST,
BECOMING SOUTHEAST TO SOUTH OVERNIGHT DUE TO THE WESTERN FLANK OF
A SLOPPY PRESSURE RIDGE REMAINING ACROSS OUR AREA.
AVIATION
(15Z TAFS)
ISSUED AT 1129 AM EDT TUE SEP 29 2026
SCATTERED TO NUMEROUS SHRA AND EMBEDDED TSRA WILL MOVE ACROSS THE
REGION THROUGH THE REMAINDER OF THE DAY WITH BRIEF MVFR/IFR
RESTRICTIONS POSSIBLE, ESPECIALLY DURING PERIODS OF HEAVIER
RAINFALL. VFR CONDITIONS WILL GENERALLY PREVAIL OUTSIDE OF ANY OF
THIS ACTIVITY WITH SE WINDS AROUND 5-10 KTS THROUGH THIS EVENING
BEFORE BECOMING MORE EASTERLY AND INCREASING TO 10-15 KTS OVERNIGHT
INTO WEDNESDAY.
KEY WATCHES/WARNINGS/ADVISORIES
FL...COASTAL FLOOD WARNING UNTIL 5 PM EDT THIS AFTERNOON FOR FLZ076.
COASTAL FLOOD ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR FLZ077-
078.
GM...NONE.
PUBLIC/MARINE/FIRE...RG
AVIATION/NOWCASTS....RG
DATA ACQUISITION.....RG
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