879
FXUS62 KKEY 170902
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
502 AM EDT WED SEP 17 2025
..NEW DISCUSSION, MARINE, AVIATION
DISCUSSION
ISSUED AT 411 AM EDT WED SEP 17 2025
CONDITIONS LOOK VERY DIFFERENT COMPARED TO LAST NIGHT AS A MESSY,
DISORGANIZED PATTERN IS DRAPED ACROSS THE AREA. OUR KBYX RADAR HAS
BEEN BUSY DETECTING SHOWER ACTIVITY AS IT CONTINUES TO TRAVERSE
OUR FORECAST AREA. SOMETHING OF NOTE ON OUR RADAR LOOP IS THE
DIRECTIONAL SHEAR ASSOCIATED WITH THIS PATTERN. SOME OF THESE
SHOWERS, PARTICULARLY OVER THE UPPER KEYS AND ADJACENT WATERS IN
HAWK CHANNEL AND THE FLORIDA STRAITS, ARE MOVING FROM EAST TO WEST
WHILE SHOWERS OVER OUR WESTERN WATERS ARE MOVING FROM SOUTH TO
NORTH. THIS JUST TELLS US THAT WE HAVE DIFFERENT WIND DIRECTIONS
AT DIFFERENT HEIGHTS IN THE ATMOSPHERE, KNOWN AS DIRECTIONAL
SHEAR. IN THE INTEREST OF KEEPING THIS DISCUSSION REASONABLY
SHORT, WE'LL OPT OUT OF BREAKING DOWN EVERY LAYER OF THE
ATMOSPHERE. A QUICK GLANCE AT CIMSS MEAN LAYER FLOW (300-850MB)
SHOWS AN AREA OF CONVERGENCE OVER THE REGION AS WE'RE SITUATED
BETWEEN A LOW TO OUR NORTH AND A HIGH TO OUR EAST. THERE IS ALSO A
MID LEVEL AREA OF VORTICITY IN THE VICINITY OF WESTERN CUBA AS
NOTED ON CIMSS VORTICITY. THESE INGREDIENTS, COUPLED WITH THE
AMPLE MOISTURE (PWAT NEAR 2 INCHES) MAKES IT NO SURPRISE THAT OUR
RADAR IS SO BUSY.
AS THIS UNSETTLED PATTERN REMAINS IN PLACE THROUGH TODAY AND INTO
TONIGHT, WIDESPREAD SHOWERS WILL CONTINUE WITH POCKETS OF EMBEDDED
THUNDERSTORMS. IT IS DIFFICULT TO HONE IN ON HOW MUCH RAINFALL ANY
ONE ISLAND COMMUNITY MAY SEE, BUT PROBABILISTIC GUIDANCE SUGGESTS
HIGHER CHANCES (75 PERCENT OR GREATER) OF RAINFALL TOTALS LESS
THAN AN INCH, AND LOWER CHANCES (25 PERCENT CHANCE OR LESS) OF
TOTALS OF 1 TO 2 INCHES OVER THE NEXT COUPLE OF DAYS. THIS TELLS
US THAT WE ARE LOOKING AT WIDESPREAD LIGHT SHOWERS WITH
OCCASIONAL, SHORT-LIVED OCCURRENCES OF HEAVIER SHOWERS.
FORECAST SOUNDINGS POINT TO DRIER AIR FILTERING INTO THE MID
LEVELS AS WE APPROACH THE END OF THE WEEK. THIS WILL HELP TO CUT
OFF SOME, BUT NOT ALL, OF OUR SHOWER ACTIVITY. WILL CONTINUE TO
ADVERTISE ELEVATED POPS THROUGH TOMORROW, FOLLOWED BY A GRADUAL
DECREASING TREND.
MARINE
ISSUED AT 411 AM EDT WED SEP 17 2025
FRESHENING NORTHEASTERLY BREEZES TODAY MAY LEAD TO SOME SMALL
CRAFT SHOULD EXERCISE CAUTION HEADLINES LATER TONIGHT,
PARTICULARLY ACROSS THE FLORIDA STRAITS, AS OUR FORECAST AREA SITS
IN A TIGHTENED PRESSURE GRADIENT. FROM SYNOPSIS, AN UNSETTLED
WEATHER PATTERN IS IN PLACE ACROSS SOUTHERN FLORIDA, AND THE
RECENT INCREASE IN SHOWERS AND THUNDERSTORMS WILL REMAIN IN PLACE
FOR THE NEXT COUPLE OF DAYS. FRESHENING NORTHEASTERLY TO EASTERLY
BREEZES WILL PEAK LATER TONIGHT, AND SMALL CRAFT SHOULD EXERCISE
CAUTION HEADLINES MAY BE NEEDED, PARTICULARLY ACROSS THE FLORIDA
STRAITS. BREEZES WILL SLACKEN BY TOMORROW, BUT SHOWERS AND
OCCASIONAL THUNDERSTORMS WILL LINGER ACROSS THE AREA THROUGH THE
END OF THE WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 411 AM EDT WED SEP 17 2025
WHILE VFR CONDITIONS ARE EXPECTED TO PREVAIL AT BOTH EYW AND MTH,
AFTER SUNRISE, SHOWERS AND THUNDERSTORMS WILL NEAR THE TERMINALS. IF
DIRECT IMPACTS ARE EXPECTED TEMPOS WILL BE INCLUDED FOR LOWER
CEILINGS AND VISIBILITIES, AND GUSTY WINDS. OUTSIDE OF CONVECTION
WINDS WILL BE NORTHEAST AT 5 TO 10 KNOTS.
CLIMATE
ON THIS DAY IN 2023, THE DAILY RECORD HIGH TEMPERATURE OF 97F WAS
RECORDED IN MARATHON. THIS IS ALSO TIED FOR THE WARMEST TEMPERATURE
EVER RECORDED IN THE MONTH OF SEPTEMBER FOR THE MARATHON AREA.
TEMPERATURES RECORDS FOR MARATHON DATE BACK TO 1950.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 89 76 88 78 / 80 80 80 60
MARATHON 88 78 87 78 / 80 80 80 60
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...DP
AVIATION/NOWCASTS....AP
DATA ACQUISITION.....AP
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