615
FXUS62 KKEY 191001
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
501 AM EST FRI DEC 19 2025
..NEW DISCUSSION, MARINE, AVIATION
KEY MESSAGES
-LIGHT TO GENTLE WEST TO NORTHWEST BREEZES WILL CONTINUE TO VEER
TO THE NORTH TO NORTHEAST BY TONIGHT.
-LIGHT WINDS AND A MOIST AIR MASS COULD PROMOTE PATCHY FOG FOR THE
ISLAND CHAIN THIS MORNING, BUT THIS IS MORE LIKELY ACROSS THE
NEARSHORE WATERS NORTH OF THE ISLAND CHAIN. IMPACTS ALONG THE
ISLAND CHAIN ARE NOT EXPECTED.
-THE BEST CHANCES FOR RAIN TODAY WILL BE DURING THE EARLY MORNING
HOURS, AND WEATHER SHOULD BE MOSTLY DRY AS WE HEAD INTO THE
WEEKEND.
DISCUSSION
ISSUED AT 450 AM EST FRI DEC 19 2025
MOST OF THE EXCITEMENT OCCURRED AT THE START OF THE OVERNIGHT
SHIFT AS SHOWERS AND THUNDERSTORMS ACROSS CENTRAL AND EASTERN
PORTIONS OF THE FLORIDA STRAITS WERE ONGOING. THERE WEREN’T ANY
RAINFALL OBSERVATIONS ALONG THE ISLAND CHAIN, BUT THIS MAY BE DUE
TO THE SPARSE NATURE OF AUTOMATED OBSERVATION SITES. MRMS SUGGESTS
THERE MAY HAVE BEEN A FEW HUNDREDTHS OF AN INCH OF RAIN IN SOME
LOCATIONS ALONG THE MIDDLE AND UPPER KEYS. NIGHTTIME MICROPHYSICS
FROM GOES-19 SHOWS A BROKEN SWATH OF CLOUD COVER ACROSS THE AREA,
BUT SURFACE OBSERVATIONS AT BOTH KEY WEST AND MARATHON
INTERNATIONAL AIRPORTS HAVE NOT REPORTED PERSISTENT CLOUD COVER.
THIS TELLS US THAT THESE CLOUDS ARE HIGHER IN ALTITUDE THROUGH THE
MID AND UPPER LEVELS, AND THIS IS IMPORTANT FOR LATER IN THIS
DISCUSSION. TEMPERATURES HAVE GENERALLY BEEN IN THE MID 70S WITH
DEW POINTS JUST BEHIND THAT, AND A LINE OF SHOWERS AND
THUNDERSTORMS OVER OUR WESTERN WATERS IS PROGRESSING EASTWARD.
IN THE VERY SHORT TERM, THE MAIN WEATHER CONCERN IS MARINE FOG,
PARTICULARLY OVER FLORIDA BAY AND THE BAYSIDE WATERS ON THE NORTH
SIDE OF THE ISLAND CHAIN. SEA SURFACE TEMPERATURES IN THAT AREA
ARE NEAR 72F TO 74F. THE DEW POINT DEPRESSION ACROSS THE SOUTHERN
TIP OF THE PENINSULA, AND ALONG THE ISLAND CHAIN, IS ANYWHERE FROM
0F TO 3F, INDICATING THAT THE AIR MASS IS NEARLY SATURATED.
IDEALLY, WE WOULD LIKE THE WATER TEMPERATURES TO BE JUST A LITTLE
BIT COOLER FOR MORE OF A “SLAM DUNK” FOG EVENT, BUT THESE
CONDITIONS MAY LEAD TO SOME PATCHY MARINE FOG. HOURLY MOS GUIDANCE
AVAILABLE FOR OUR AVIATION SITES POINT TO A VERY LOW PROBABILITY
OF REDUCED VISIBILITY THIS MORNING (LESS THAN 10 PERCENT CHANCE),
WHICH IS USUALLY INDICATIVE OF FOG. THERE ARE TWO CAVEATS WITH
THIS FOG FORECAST. EARLIER WE MENTIONED THAT THERE IS A SWATH OF
MID TO UPPER LEVEL CLOUDS ACROSS THE AREA, AND THIS INCLUDES THE
AREA WHERE WE SUSPECT FOG MAY FORM. WHILE SATELLITE-DERIVED
PRODUCTS DO HELP US SEE FOG WHEN IT OCCURS, THESE CLOUDS WILL
OBSTRUCT THE VIEW OF THE SEA SURFACE. THERE ARE ALSO NO
OBSERVATION PLATFORMS ACROSS FLORIDA BAY THAT REPORT VISIBILITY,
SO IF FOG OCCURS UNDER THESE MARGINAL CONDITIONS, WE MAY NOT GET
ANY GROUND TRUTH TO CONFIRM IT. REGARDLESS, WE WILL KEEP PATCHY
FOG IN THE FORECAST FOR THIS MORNING EVEN WITH THE UNCERTAINTY
THAT EXISTS.
FOR TODAY, A WEAK BOUNDARY SAGGING DOWN THE FLORIDA PENINSULA
WILL NOT MEAN TOO MUCH FOR OUR SENSIBLE WEATHER. BREEZES WILL
CONTINUE TO VEER FROM THE SOUTHWEST TO WEST THIS MORNING TO THE
NORTHWEST TO NORTH LATER. LOW LEVEL MOISTURE AHEAD OF THE FRONT
SEEMS AMPLE ENOUGH TO ENCOURAGE SOME SHOWER ACTIVITY NEAR THE
ISLAND CHAIN. 10 PERCENT POPS ALMOST SEEMS A LITTLE TOO LOW, BUT
20 PERCENT SEEMS A LITTLE TOO HIGH. OPTING TO ADVERTISE 10 PERCENT
IN THE ZONE FORECAST WITH THE DISCLAIMER HERE THAT IT’S MORE OF A
“HIGHER” 10 PERCENT. WITH THE ABOVE-NORMAL MOISTURE IN THE LOWER
LEVELS COUPLED WITH SLIGHT VEERING OF THE WINDS, SHOWERS ARE GOING
TO HAPPEN SOMEWHERE IN THE CWA, IT’S JUST A MATTER OF WHERE. THIS
FRONT, OR WHAT IS LEFT OF IT, WILL LIFT OUT OF THE AREA TONIGHT,
AND HIGHER PRESSURE WILL BUILD IN. THIS WILL HELP TO KEEP WEATHER
OVER THE WEEKEND CALM AND QUIET WITH TEMPERATURES JUST A COUPLE OF
DEGREES WARMER THAN AVERAGE.
OVER THE START OF THE NEW WORK WEEK, LOW LEVEL RIDGING WILL
AMPLIFY ALONG THE EASTERN U.S. AND GUIDANCE POINTS TO A CHANGE IN
THE SENSIBLE WEATHER, PARTICULARLY SURFACE WINDS. WITH THE
NORTHEASTERLY FLOW, THIS MAY BE A BACKDOOR FRONT APPROACHING THE
AREA. THE TIGHTENING SURFACE GRADIENT COULD LEAD TO BREEZY, OR
EVEN WINDY, CONDITIONS FROM MONDAY THROUGH WEDNESDAY. SPEED
CONVERGENCE COUPLED WITH LOW LEVEL MOISTURE COULD PRODUCE A FEW
LIGHT SHOWERS AS WELL, SO OPTING TO THROW IN LOW END POPS JUST IN
CASE. SANTA’S REINDEER ARE CLEARED TO FLY IN THESE ELEVATED WINDS,
SO WE DO NOT HAVE ANY CONCERNS WITH REGARD TO THE HOLIDAY.
MARINE
ISSUED AT 450 AM EST FRI DEC 19 2025
THERE ARE NO WATCHES, WARNINGS, OR ADVISORIES IN EFFECT FOR THE
FLORIDA KEYS LOCAL WATERS. FROM SYNOPSIS, A WEAK FRONT WILL PUSH
THROUGH THE FLORIDA KEYS COASTAL WATERS TODAY, AND OUR GENERALLY
LIGHT TO GENTLE WESTERLY BREEZES THIS MORNING WILL VEER TO THE
NORTH BY TONIGHT. MODESTLY FRESHENED BREEZES ARE EXPECTED FOR THE
WEEKEND IN ITS WAKE. ANOTHER HIGH BUILDING OVER THE EASTERN
SEABOARD WILL SUPPORT FRESH TO STRONG BREEZES FOR EARLY TO MID
WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 450 AM EST FRI DEC 19 2025
VFR CONDITIONS ARE EXPECTED TO PREVAIL AT BOTH EYW AND MTH
TERMINALS THROUGH THE TAF PERIOD. A WEAKENING FRONTAL BOUNDARY IS
EXPECTED TO PASS THROUGH THE KEYS SOMETIME LATE TODAY OR THIS
EVENING. LATEST GUIDANCE SHOWS SOME WEAK CONVECTION OUT AHEAD OF
THE FRONT WITH THE POTENTIAL FOR A PASSING SHOWER AROUND 19/18Z.
HOWEVER, DUE TO THE UNCERTAIN NATURE IN THE STRENGTH AND PLACEMENT
OF THIS ACTIVITY, VCSH WAS LEFT OUT OF THE TAF FOR NOW. WINDS
WILL BECOME NORTHWEST TO NORTH BETWEEN 5 TO 10 KNOTS THIS
AFTERNOON BEFORE FURTHER SHIFTING TO THE NORTH OVERNIGHT.
CLIMATE
ON THIS DAY IN 2016, THE DAILY RECORD WARM LOW TEMPERATURE OF 77F
WAS RECORDED IN KEY WEST. TEMPERATURE RECORDS FOR KEY WEST DATE BACK
TO 1872.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 82 69 79 71 / 10 0 0 10
MARATHON 79 69 78 72 / 10 0 10 10
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...DP
AVIATION/NOWCASTS....MJV
DATA ACQUISITION.....MJV
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