842
FXUS62 KKEY 281836
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
236 PM EDT MON SEP 28 2026
..NEW AVIATION
KEY MESSAGES
- MINOR TO MODERATE 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 ALL OF THE FLORIDA
KEYS THROUGH TUESDAY MORNING.
- 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
AVIATION
(18Z TAFS)
ISSUED AT 234 PM EDT MON SEP 28 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE REMAINDER OF THE DAY WITH
SW WINDS AROUND 5-7 KTS. WINDS WILL INCREASE TO 7-10 KTS
OVERNIGHT INTO TUESDAY MORNING AND BECOME MORE SOUTHEASTERLY. IN
ADDITION, DEEPER MOISTURE WILL ALSO SPREAD INTO THE REGION WITH
CHANCES OF SCATTERED SHRA/TSRA INCREASING OVERNIGHT INTO TUESDAY
AND VCTS IS IN PLACE AFTER 08Z THROUGH THE END OF THE TAF PERIOD.
THUS, BRIEF FLIGHT RESTRICTIONS TO MVFR/IFR MAY OCCUR AFTER THIS
TIME IF PRECIP ACTIVITY DIRECTLY IMPACTS EITHER OF THE TERMINALS.
UPDATE
ISSUED AT 1144 AM EDT MON SEP 28 2026
THE 12Z KEY RAOB SHOWS A VERY DRY ATMOSPHERIC PROFILE, ESPECIALLY
IN THE MID LEVELS WITH A MID LEVEL RH VALUE OF JUST 21% AND A
SUBSTANTIAL DRY LAYER IN THE 850-350 MB LAYER. ADDITIONALLY, A
PWAT VALUE OF 1.13 WAS SAMPLED AND THIS VALUE IS BELOW THE 10TH
PERCENTILE FOR LATE SEPTEMBER. HOWEVER, TODAY IS THE FINAL DAY OF
THE BRIEF REPRIEVE FROM THE EXTREME SUMMER-TIME HUMIDITY FOR THE
FLORIDA KEYS AS DEEPER MOISTURE COMES SURGING BACK LATER TODAY
INTO TONIGHT AHEAD OF A SHARPENING TROUGH AXIS POSITIONED IN THE
EASTERN GULF AND EXTENDING INTO THE YUCATAN REGION. LATEST
SATELLITE IMAGERY SHOWS A LARGE CLUSTER OF CONVECTION IN THE
SOUTHERN GULF WATERS AROUND THE BASE OF THIS FEATURE AND IN THE
VICINITY OF A REMNANT FRONTAL BOUNDARY. THIS ACTIVITY COMBINED
WITH CONVECTION THAT FIRES ALONG CUBA LATER TODAY SHOULD GENERALLY
ADVANCE TOWARDS THE FLORIDA KEYS BY TONIGHT ALONG THE LEADING EDGE
OF DEEPER MOISTURE ADVECTION, THOUGH THIS SHOULD PRIMARILY BE IN
A WEAKENING FASHION AS SOME STABILIZATION OCCURS THIS EVENING.
HOWEVER, GIVEN PLENTY OF FORCING FOR ASCENT, ENHANCED DIVERGENCE
ALOFT, AND THE RETURN OF TROPICAL MOISTURE, ADDITIONAL ACTIVITY
SHOULD BE ABLE TO DEVELOP LATE EVENING AND OVERNIGHT, WHICH COULD
MAKE FOR WET AND STORMY CONDITIONS AT TIMES TONIGHT INTO TUESDAY.
OTHERWISE, BEFORE THE DEEPER MOISTURE ARRIVES, IT SHOULD BE A DRY
AHEAD WITH HIGHS IN THE MID/UPPER 80S AND ONE FINAL DAY OF SUB-70
DEWPOINTS BEFORE DEWPOINTS QUICKLY SURGE TO THE MID TO UPPER 70S
THROUGH MID WEEK. THE ONLY OTHER ITEM OF NOTE FROM THE MORNING
UPDATE WAS CANCELING THE COASTAL FLOOD WARNING IN THE UPPER KEYS
IN FAVOR OF A COASTAL FLOOD ADVISORY FOR THE ENTIRE ISLAND CHAIN
THROUGH TUESDAY MORNING BASED ON RECENT OBSERVATIONS SHOWING MINOR
TO MODERATE SALTWATER FLOODING IN THE REGION.
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
A NOR'EASTER IN THE NEW ENGLAND STATES WILL CONTINUE TO MAINTAIN A
LINGERING NORTHERLY SWELL IN OUR FAR EASTERN WATERS BEFORE
SUBSIDING THROUGHOUT THE DAY. A WEAK FRONTAL BOUNDARY WILL LIFT
NORTHWARD ACROSS THE KEYS TODAY. THIS WILL ALLOW WEST TO NORTHWEST
WINDS TO BACK TO THE SOUTH AND SOUTHWEST AND EVENTUALLY TO THE
SOUTHEAST TO SOUTH THIS EVENING. WINDS THEN BECOME MORE EASTERLY
BY TUESDAY AS A HIGH PRESSURE MOVES INTO THE EASTERN U.S.
THEREAFTER, THIS HIGH WILL MERGE WITH AN EXISTING HIGH PRESSURE
ACROSS THE ATLANTIC AND SUBSEQUENTLY WILL BUILD. THIS WILL PROMOTE
FRESHENING BREEZES, WITH AN INCREASING LIKELIHOOD OF MODERATE TO
FRESH BREEZES FOR THE LATTER HALF OF THE WEEK.
KEY WATCHES/WARNINGS/ADVISORIES
FL...COASTAL FLOOD ADVISORY UNTIL 5 AM EDT TUESDAY FOR FLZ076>078.
GM...NONE.
PUBLIC/MARINE/FIRE...RG
AVIATION/NOWCASTS....RG
DATA ACQUISITION.....JY
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