872
FXUS62 KKEY 181537
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1037 AM EST THU DEC 18 2025
..NEW DISCUSSION, MARINE, AVIATION, PREV DISCUSSION
KEY MESSAGES
-MODERATE EASTERLY BREEZES WILL SLACKEN AND VEER TOWARDS THE
SOUTH THIS AFTERNOON AS HIGH PRESSURE ALONG THE EASTERN SEABOARD
SLIDES INTO THE NORTH ATLANTIC.
-RAIN CHANCES MODESTLY INCREASE THIS EVENING, WITH THUNDER ALSO
POSSIBLE TONIGHT AHEAD OF A WEAK FRONTAL PASSAGE.
-OUTSIDE OF MODESTLY FRESHENED BREEZES, MINIMAL CHANGES TO THE
SEASONABLY WARM CONDITIONS ARE EXPECTED IN THE WAKE OF THE FRONT.
DISCUSSION
VERY QUIET START TO THE FLORIDA KEYS. A HIGH PRESSURE IS MOVING
OFF THE MID-ATLANTIC COAST AND SHIFTING OUT ACROSS THE ATLANTIC.
AS A RESULT OUR WINDS HAVE BEEN CLOCKING AROUND TO THE SOUTHEAST
THIS MORNING. WE ARE SEEING SOME STRATO-CU DEVELOP THIS MORNING IN
THE SOUTHEAST FLOW BUT NOTHING OF SIGNIFICANCE RIGHT NOW. THIS
MORNING SOUNDING DID SHOW AN UPTICK IN THE LAYER MOISTURE FROM 12
HOURS AGO. THAT BEING SAID, A COUPLE INVERSIONS AND ISOTHERMAL
LAYERS WERE NOTED ON THE SOUNDING. MEANWHILE, AN UPPER LEVEL
TROUGH MOVING ACROSS THE GULF BASIN IS ALLOWING ADDITIONAL CLOUDS
AND MOISTURE TO STREAM IN OVERHEAD FROM THE SOUTHWEST.
THE MAIN QUESTION FOR THIS AFTERNOON IS WHETHER WE CAN OVERCOME
THE STABILITY CURRENTLY IN PLACE. KBYX RADAR SHOWS A RESIDUAL LAND
BREEZE THAT CAME OFF OF CUBA, PIVOTING THROUGH OUR SOUTHWESTERN
WATERS. THIS FEATURE HOWEVER, HAS ONLY PRODUCE MAYBE A BRIEF
SHOWER AT BEST. TO COMPLICATE THINGS, WE HAVE A GOOD VEERING
PROFILE WITH SOUTHEAST SURFACE WINDS, QUICKLY BECOMING SOUTHWEST
TO WEST ALOFT. AT THE SAME TIME, MID AND UPPER LEVEL CLOUDS MOVING
IN WILL LIKELY DISRUPT ANY ADDITIONAL MIXED LAYER INSTABILITY.
GIVEN THE ALL OF THESE PARAMETERS, HAVE MADE THE DECISION TO LOWER
POPS TO 10 PERCENT FROM THE PREVIOUSLY ADVERTISED 20 PERCENT.
MARINE
ISSUED AT 1037 AM EST THU DEC 18 2025
A VAST DIFFERENCE IN SOUTHEAST BREEZES ACROSS THE FLORIDA KEYS
WATERS THIS MORNING. ALONG AND SOUTH OF THE REEF AND THE OUTER
GULF WATERS, WE HAVE MODERATE BREEZES, WHILE NORTH OF THE ISLAND
CHAIN, WE HAVE GENTLE TO MODERATE, AND EVEN SOME LIGHT TO GENTLE
BREEZES IN SPOTS. AS A HIGH PRESSURE CONTINUES TO PUSH OUT ACROSS
THE ATLANTIC IN ADVANCE OF AN APPROACHING WEATHER SYSTEM, WINDS
WILL CONTINUE TO BOX AROUND THE COMPASS THIS AFTERNOON AND
EVENING. THE ASSOCIATED COLD FRONT WILL BE IN A WEAKENED STATE
WHEN IT REACHES THE KEYS LATE TONIGHT INTO FRIDAY. A DECAYING LINE
OF SHOWERS AND POSSIBLY ISOLATED THUNDERSTORMS WILL BE PRECEEDING
THIS FRONT. IN THE MEANTIME, YOU CAN EXPECT INCREASING CLOUDS AND
POSSIBLE ISOLATED SHOWERS AT TIMES THROUGH THIS AFTERNOON AND
EVENING.
AVIATION
(15Z TAFS)
ISSUED AT 1037 AM EST THU DEC 18 2025
VFR CONDITIONS WILL PREVAIL. A STRATO-CU DECK HAS DEVELOPED IN THE
SOUTHEAST FLOW AND WILL OCCASIONALLY PASS OVER BOTH TERMINALS
THROUGH THE AFTERNOON AND EVENING. WINDS WILL GRADUALLY VEER
TOWARDS THE SOUTH THIS AFTERNOON AND EARLY EVENING, THEN BECOMING
SOUTHWEST TO WEST TOWARDS DAWN FRIDAY. CONFIDENCE REMAINS TOO LOW
AT THIS TIME TO INCLUDE MENTIONS OF VCSH AND WILL LEAVE FOR FUTURE
AMENDEMENTS.
PREV DISCUSSION
ISSUED AT 448 AM EST THU DEC 18 2025
ANOTHER QUIET MORNING IS UNDERWAY ACROSS THE FLORIDA KEYS. KBYX
RADAR IS ONCE AGAIN FREE OF PRECIPITABLE ECHOES IN OUR AREA.
GOES-19 NIGHTTIME MICROPHYSICS IMAGERY SHOWS A MIX BETWEEN PATCHES
OF WESTERLY MOVING FAIR WEATHER CUMULUS IN THE EASTERN STRAITS AND
HIGH CIRRUS STREAKING NORTHEAST ACROSS THE GULF. MODERATE EASTERLY
BREEZES PERSIST ALONG THE REEF HAVING CHANGED VERY LITTLE OVER THE
LAST FEW HOURS. TEMPERATURES ALONG THE ISLAND CHAIN ARE A COUPLE
DEGREES WARMER THAN YESTERDAY AROUND THIS TIME AND RANGE IN THE
LOWER TO MID 70S WITH DEWPOINTS NEAR 70.
SOME CHANGE IN PATTERN IS FORECAST IN THE SHORT TERM. AN ELONGATED
SURFACE HIGH STRETCHING FROM THE SOUTHEAST US INTO THE WESTERN
NORTH ATLANTIC WILL LIFT NORTHEAST AND START LOSING ITS GRIP ON
OUR SENSIBLE WEATHER TODAY. AS A RESULT, EASTERLY BREEZES WILL
GRADUALLY SLACKEN AND VEER TO THE SOUTHEAST THROUGHOUT THE DAY.
WHILE BREEZES WILL BE TURNING TO MORE MOIST SURFACE WIND, A LARGE
POCKET OF DRY AIR STILL EXITS IN THE LOWER TO MID LEVEL JUST
ABOVE THE INVERSION OBSERVED IN OUR 00Z KKEY BALLOON SOUNDING LAST
NIGHT. THUS HAVE OPTED TO KEEP SLIGHT CHANCE POPS TODAY.
TONIGHT COULD GET A LITTLE MORE INTERESTING AS THE LOWER TO MID
LEVEL PROFILE MOISTENS UP. FORECAST SOUNDINGS INDICATE DECENT (FOR
THIS TIME OF YEAR) LOW LEVEL SHEAR AND MODESTLY UNCAPPED
INSTABILITY. THAT BEING SAID, FORCING WILL BE SOMEWHAT NEBULOUS AS
WINDS ARE EXPECTED TO BE ON A DOWNWARD TREND WITH NO APPARENT
SOURCES OF SYNOPTIC LIFT. CAMS DO SUGGEST SOME ISOLATED CONVECTION
MAY FORM DESPITE THESE LIMITING FACTORS, SO HAVE OPTED TO GO WITH
CHANCE POPS AND A SLIGHT CHANCE OF THUNDERSTORMS JUST IN CASE.
OUR SENSIBLE WEATHER PATTERN WILL CONTINUE TO CHANGE THIS WEEKEND
AS A COLD FRONT APPROACHES LATE FRIDAY. BREEZES WILL CLOCK ALL
THE WAY BACK AROUND TO THE NORTH, BUT DUE TO THE WEAK NATURE OF
THE FRONT TEMPERATURES WILL ONLY SEE A FEW DEGREES OF DIFFERENCE
FROM PREVIOUS DAYS. BY THE START OF NEXT WEEK, HIGH PRESSURE WILL
BUILD BACK ALONG THE EAST COAST OF CONUS WITH BREEZY CONDITIONS
DEVELOPING MONDAY AND POSSIBLY BECOMING WINDY INTO TUESDAY. WHILE
THIS SOLUTION HAS BEEN RELATIVELY STABLE, THERE IS STILL PLENTY OF
TIME FOR SOME CHANGES TO THE FORECAST SO STAY TUNED.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 82 73 81 70 / 10 30 20 10
MARATHON 80 73 80 70 / 10 30 20 10
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...LIW
AVIATION/NOWCASTS....LIW
DATA ACQUISITION.....LIW
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