778
FXUS62 KKEY 050232
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1032 PM EDT THU SEP 4 2025
..NEW DISCUSSION, MARINE, AVIATION
DISCUSSION
ISSUED AT 1000 PM EDT THU SEP 4 2025
TODAY WAS ONE OF THE RARE DAYS WHERE THE FLORIDA KEYS WERE SOCKED
IN WITH CLOUD COVER AND ONE AND OFF SHOWER ACTIVITY ALL DAY.
TOTAL RAINFALL AMOUNTS REPORTED FROM AVAILABLE GAUGE DATA RANGED
FROM AROUND 1-4" IN THE LOWER KEYS, 0.5-1.5" IN THE MIDDLE KEYS,
AND BETWEEN 0.25-0.5" IN THE UPPER KEYS. SIMILAR TO THE PAST
SEVERAL DAYS, CONVECTION WANED IN THE EARLY EVENING HOURS, LEAVING
THE ENTIRE ISLAND CHAIN CURRENTLY DRY AND UNDER PARTLY CLOUDY
SKIES. THE 00Z EVENING SOUNDING AT KEY REVEALED A SURPRISING
STABLE, DRY LAYER FROM THE SURFACE UP TO AROUND 700 MB, CONSISTENT
WITH SUBSTANTIAL INHIBITION AND MINIMAL MIXED LAYER INSTABILITY.
WE HYPOTHESIZE THAT THIS IS DERIVED FROM LOCALLY-INDUCED DRY
ADIABATIC SUBSIDENCE FROM THE COPIOUS AMOUNT OF CONVECTION TODAY,
RATHER THAN INDUCED BY SYNOPTIC ADVECTION OF UPSTREAM DRY AIR.
GIVEN THE LOCAL SOURCE OF THE SUBSIDENCE, AND THE FACT THAT THE
FRONTAL BOUNDARY TO OUR NORTH HAS MADE LITTLE MOVEMENT, WE EXPECT
RESTORATION AND CHARGING TO OCCUR OF THE LOW-LEVELS OVERNIGHT,
WITH ANOTHER ROUND OF SCATTERED TO WIDESPREAD CONVECTION EMERGING
BY THE LATE OVERNIGHT HOURS IN THE VICINITY OF THE KEYS. IN
ADDITION, MOST NUMERICAL WEATHER PREDICTION GUIDANCE SUGGESTS
SOUTH TO SOUTHWESTERLIES CLOCKING AROUND TO THE SOUTHWEST TO WEST
FROM WEST TO EAST AROUND SUNRISE, WHICH WILL SUPPORT CONFLUENCE
AND ADDITIONAL FORCING FOR ASCENT. GIVEN THIS REASONING, HAVE
ELECTED TO RETAIN THE LIKELY POPS FOR THE OVERNIGHT HOURS. OUTSIDE
OF MINOR ADJUSTMENTS TO WIND SPEEDS AND DIRECTIONS EARLY IN THE
OVERNIGHT PERIOD, NO CHANGES MADE TO THE INHERITED FORECAST.
MARINE
ISSUED AT 1000 PM EDT THU SEP 4 2025
SIMILAR TO THE PAST SEVERAL NIGHTS, SHOWER AND THUNDERSTORM
ACTIVITY IS UNDER A LULL CURRENTLY ACROSS THE KEYS MARINE ZONES.
HOWEVER, ADDITIONAL ACTIVITY IS EXPECTED TO DEVELOP BY LATE
TONIGHT. ANY STRONGER STORM WILL PRODUCE LOCALLY GUSTY WINDS,
CLOUD TO SURFACE LIGHTNING STRIKES, AND CONFUSED SEAS.
FROM SYNOPSIS, A BROAD SURFACE LOW ALONG A STATIONARY FRONT
STRETCHING FROM THE GULF EASTWARD TO THE FLORIDA PENINSULA WILL
MAINTAIN SOUTHWESTERLY WINDS ACROSS THE FLORIDA KEYS MARINE ZONES.
THE FRONT WILL REMAIN ROOTED IN PLACE THROUGH THE NEXT FEW DAYS,
WHILE THE LOW MEANDERS NORTHEAST INTO THE WESTERN NORTH ATLANTIC,
PROMOTING SOUTHWEST TO WEST BREEZES. ABUNDANT MOISTURE WILL
PROMOTE WELL ABOVE NORMAL RAIN AND THUNDER CHANCES THROUGH THE END
OF THE WORK WEEK. HIGH PRESSURE SLOWLY BUILDING ACROSS THE NORTH
ATLANTIC OVER THE WEEKEND WILL SUPPORT REDUCED RAIN AND THUNDER
CHANCES, ALTHOUGH REMAINING AT OR ABOVE NORMAL.
AVIATION
(00Z TAFS)
ISSUED AT 1000 PM EDT THU SEP 4 2025
A CONVECTIVE LULL CURRENTLY IN THE VICINITY OF THE ISLAND
TERMINALS IS EXPECTED TO CONTINUE THROUGH AT LEAST 06Z, BEFORE
ADDITIONAL SHOWERS AND STORMS ARE EXPECTED TO FORM AND PUSH TO
EYW AND MTH THEREAFTER, LIKELY LASTING THROUGH MUCH OF THE REST OF
THE 00Z TAF PERIOD. HAVE ELECTED TO JUST REINTRODUCE A GENERAL
PERIOD OF VCSH AFTER 06Z AT EYW AN 09Z AT MTH, WITH SPECIFIC
IMPACTS TO VISIBILITIES AND CEILINGS TO BE HANDLED BY LATER TAF
AMENDMENTS. THIS WILL BE REEVALUATED AT THE 06Z TAF FORECAST
CYCLE.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 79 91 80 91 / 60 80 50 50
MARATHON 79 89 80 89 / 60 80 50 50
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...BT
AVIATION/NOWCASTS....BT
DATA ACQUISITION.....MJV
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