240
FXUS62 KKEY 191555
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1055 AM EST FRI DEC 19 2025
..NEW DISCUSSION, MARINE, AVIATION, PREV DISCUSSION
KEY MESSAGES
-LIGHT TO GENTLE WEST TO NORTHWEST BREEZES WILL CONTINUE TO VEER
TO THE NORTH TO NORTHEAST BY TONIGHT.
-DRIER AIR IS MOVING IN AND CHANCE FOR RAIN ARE QUICKLY DWINDLING.
DISCUSSION
ISSUED AT 1055 AM EST FRI DEC 19 2025
THE COLD FRONT IS FINALLY MARCHING ACROSS THE FLORIDA KEYS THIS
MORNING. WINDS HAVE BEGUN VEERING OUT OF THE WEST AND NORTHWEST IN
KEY WEST, WHILE STILL SOUTHWEST TO WEST ACROSS THE MIDDLE AND
UPPER KEYS. AHEAD OF THE FRONT WE DID HAVE A FOG BANK DEVELOP
ACROSS THE BAYSIDE WATERS. TRAFFIC CAMERAS BRIEFLY SHOWED A THICK
LOCALIZED FOG BANK OVER THE WATERS SURROUNDING THE SEVEN MILE
BRIDGE. MEANWHILE, THE THIN LINE OF SHOWERS AND ISOLATED
THUNDERSTORMS THAT THE KBYX RADAR WAS TRACKING HAVE DISSIPATED AND
ALL BUT FIZZLED OUT.
GOING FORWARD TODAY, THE FRONT WILL CONTINUE TO MOVE EAST AND
SOUTHEAST ACROSS THE REMAINING PORTIONS OF OUR CWA AND COASTAL
WATERS. THIS WILL LEAD TO WIDESPREAD NORTHWEST WINDS BY THIS
AFTERNOON. ANY ADDITIONAL SHOWERS THAT MANAGE TO DEVELOP WILL
LIKELY BE CONTAINED TO THE STRAITS OF FLORIDA. HOWEVER, GIVEN THAT
THE FRONT STILL NEEDS TO PUSH THROUGH THE MIDDLE AND UPPER KEYS,
HAVE MAINTAINED AT LEAST A 10 PERCENT FOR THESE COMMUNITIES.
OTHERWISE, DRIER AIR INVADING BEHIND THE FRONT WILL SHUTDOWN MOST
OF OUR RAIN CHANCES AT LEAST TEMPORARILY. AS A HIGH BUILDS IN
BEHIND THIS FRONT, WINDS WILL CLOCK AROUND AND BE OUT OF THE NORTH
TO NORTHEAST BY TONIGHT. DESPITE THE WEAK COLD AIR ADVECTION, A
SURGE OFF THE MAINLAND OVERNIGHT IS VERY POSSIBLE AND WILL
REEVALUATE FOR THIS AFTERNOON.
MARINE
ISSUED AT 1055 AM EST FRI DEC 19 2025
COLD FRONT CURRENTLY DRAPED NORTHEAST TO SOUTHWEST FROM NEAR THE
FLORIDA BAY TO THE STRAITS OF FLORIDA, WILL CONTINUE TO PUSH
EASTWARD THROUGH THE AFTERNOON. IN THE WAKE OF THE FRONTAL
PASSAGE, SOUTHWEST TO WEST BREEZES WILL BECOME NORTHWEST AND
FRESHEN THROUGH THE AFTERNOON. FURTHER VEERING AND FRESHENING IS
EXPECTED AS A HIGH BUILDS IN BEHIND THIS EVENING. THIS WILL
PROMOTE A WEAK NOCTURNAL SURGE OFF THE MAINLAND. OTHERWISE,
ANY LINGERING MORNING FOG ACROSS THE BAYSIDE WATERS WILL QUICKLY
DISSIPATE AS BREEZES FRESHEN. A THREAT FOR ISOLATED SHOWERS WILL
CONTINUE IN THIS AFTERNOON, MOSTLY FOR THE STRAITS OF FLORIDA.
AVIATION
(15Z TAFS)
ISSUED AT 1055 AM EST FRI DEC 19 2025
VFR CONDITIONS EXPECTED TO PREVAIL THROUGH THE FORECAST PERIOD.
WINDS AT EYW HAVE BEGUN TO VEER OUT OF THE WEST AND NORTHWEST.
WINDS AT MTH ARE BEGINNING TO VEER TOWARDS THE WEST AND WILL
FURTHER VEER THROUGH THE AFTERNOON. WIND SPEEDS WILL FRESHEN
SLIGHTLY THIS AFTERNOON AND FURTHER FRESHEN OVERNIGHT DUE TO A
WEAK NOCTURNAL SURGE OFF THE MAINLAND.
PREV 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.
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...LIW
AVIATION/NOWCASTS....LIW
DATA ACQUISITION.....LIW
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