858
FXUS62 KKEY 120241
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1041 PM EDT THU SEP 11 2025
..NEW DISCUSSION, MARINE, AVIATION
DISCUSSION
ISSUED AT 1030 PM EDT THU SEP 11 2025
KBYX RADAR HAS BEEN ACTIVE ALL EVENING WITH THE PAST HOUR BETWEEN
9-10PM BEING ESPECIALLY BUSY. THE MID TO LATE AFTERNOON BEGAN
WITH SOME SHOWERS AND AN OCCASIONAL THUNDERSTORM ACROSS FLORIDA
BAY AND THE UPPER KEYS WITH ADDITIONAL SHOWER ACTIVITY JUST
OFFSHORE THE LOWER KEYS AND ACROSS THE OFFSHORE GULF WATERS
SURROUNDING THE DRY TORTUGAS. CONVECTION ON THE SOUTHERN MAINLAND
SENT AN OUTFLOW BOUNDARY SOUTH TO SOUTHWESTWARD INTO THE FLORIDA
KEYS COASTAL WATERS AS WELL AS THE ISLAND CHAIN. IN DOING SO, IT
GENERATED A WIND GUST OF 36 KNOTS OR 41 MPH AT CARYSFORT REEF
LIGHT EARLIER THIS EVENING (~650 PM EDT). AFTER THE BOUNDARY
PASSED THROUGH, RESIDUAL SHOWER AND THUNDERSTORM ACTIVITY
DEVELOPED IN ITS WAKE. THIS PRODUCED A TRAINING SETUP ACROSS THE
UPPER KEYS, IN PARTICULAR, BETWEEN CRAIG KEY AND THE ISLAMORADA
AREA. MRMS DATA HAS DETECTED RAINFALL AMOUNTS OF 2-3 INCHES IN A
ONE HOUR TIME FRAME. THIS HAS RESULTED IN A FLOOD ADVISORY BEING
ISSUED FOR THE AREA UNTIL 1130 PM EDT. IN ADDITION, AS THIS
BOUNDARY HAS CONTINUED MOVING TO THE SOUTH TO SOUTHWEST, MORE
SHOWERS AND THUNDERSTORMS HAVE FORMED IN ITS WAKE ACROSS THE
OFFSHORE GULF WATERS TO THE EASTERN PORTION OF THE LOWER KEYS,
MIDDLE KEYS, AND ACROSS CENTRAL HAWK CHANNEL AND THE STRAITS OF
FLORIDA. ONE OF THE STORMS NEAR ALLIGATOR REEF LIGHT GOT INTENSE
ENOUGH TO WARRANT A SPECIAL MARINE WARNING FROM AROUND 950 PM TO
1030 PM EDT. TEMPERATURES ALONG THE ISLAND CHAIN ARE IN THE LOWER
TO MID 80S WITH MID TO UPPER 70S FOR MUCH OF THE UPPER KEYS. DEW
POINTS ARE IN THE MID TO UPPER 70S.
A STATIONARY FRONT REMAINS DRAPED ACROSS SOUTH FLORIDA WITH MUCH
OF THE KEYS REMAINING JUST SOUTH OF THE FRONT FOR NOW. DUE TO THE
CONVECTION TONIGHT, MARINE PLATFORMS ARE OBSERVING A VARIETY OF
DIFFERENT WINDS. MARINE PLATFORMS AROUND THE LOWER KEYS ARE
OBSERVING NORTHWEST TO NORTH BREEZES OF 5 TO 10 KNOTS, WHILE THE
OTHER MARINE PLATFORMS ARE OBSERVING NORTH TO NORTHEAST BREEZES OF
15 TO 20 KNOTS DUE TO THUNDERSTORMS IN THE VICINITY.
SHORT TERM FORECAST
THE 00Z EVENING SOUNDING REMAINS QUITE SATURATED THROUGH THE
COLUMN. THE PWAT VALUE MEASURED WAS 2.11 INCHES WHICH IS JUST
BELOW THE 90TH PERCENTILE FOR THE DATE. THE WIND PROFILE WOULDN'T
BE AN IDEAL SETUP FOR SHOWERS WITH WEST TO NORTHWEST WINDS FROM
THE SURFACE UP TO AROUND 3000 FT AGL. HOWEVER, WE DO HAVE THE
INGREDIENTS IN PLACE TONIGHT FOR AN ACTIVE RADAR. WE HAVE THE
OUTFLOW BOUNDARY AND A ROBUST ONE AT THAT FROM EARLIER CONVECTION
OVER MAINLAND SOUTH FLORIDA MOVING SOUTH TO SOUTHWEST. PLENTY OF
MOISTURE REMAINS IN PLACE AS WELL AS INSTABILITY. GIVEN ALL 3 OF
THESE, WE WOULD EXPECT SHOWERS AND THUNDERSTORMS TO CONTINUE TO
DEVELOP AS THIS OUTFLOW BOUNDARY CONTINUES TO PROPAGATE SOUTH TO
SOUTHWESTWARD OVERNIGHT.
MARINE
ISSUED AT 1030 PM EDT THU SEP 11 2025
THERE ARE CURRENTLY NO WATCHES, WARNINGS, OR ADVISORIES IN EFFECT
ACROSS THE FLORIDA KEYS COASTAL WATERS. FROM SYNOPSIS, A WEAK
SURFACE TROUGH REMAINS DRAPED ACROSS SOUTH FLORIDA. THIS WILL KEEP
A VERY MOIST AND UNSETTLED ENVIRONMENT ACROSS OUR AREA. A STALLED
FRONT ACROSS FLORIDA IS EXPECTED TO SLIDE SOUTHWARD INTO THE
STRAITS THIS WEEKEND. AS A RESULT, RAIN CHANCES WILL REMAIN
ELEVATED WHILE WINDS FIRM UP SLIGHTLY AND CLOCK FROM NORTHWEST TO
NORTHEAST. WITH THAT SAID, THERE IS CONSIDERABLE UNCERTAINTY AS
STRONGER BREEZES WILL NOT BE FAR OFF TO THE NORTH AND LIGHT AND
VARIABLE BREEZES ARE EXPECTED JUST TO OUR EAST.
AVIATION
(00Z TAFS)
ISSUED AT 1030 PM EDT THU SEP 11 2025
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. LATEST
GUIDANCE SHOWS THE TERMINALS REMAINING DRY FOR THE MOST PART
OVERNIGHT WITH THE THREAT FOR SHOWERS AND THUNDERSTORMS NOT UNTIL
SOMETIME AFTER 12/12Z. HOWEVER, GIVEN THE CURRENT ENVIRONMENT
TONIGHT AND MULTIPLE BOUNDARIES THROUGHOUT THE REGION, SHOWERS AND
THUNDERSTORMS MAY OCCUR AT THE TERMINALS EARLIER THAN CURRENTLY
PROJECTED. FOR NOW, WE WENT WITH VCSH IN THE TAF FOR 12/12Z AND
AFTER, BUT, THIS MAY BE ADJUSTED IN SUBSEQUENT UPDATES. NEAR
SURFACE WINDS WILL REMAIN MOSTLY NORTHWEST TO NORTH BETWEEN 2 AND
8 KNOTS WITH HIGHER GUSTS IN AND AROUND CONVECTION.
PRELIMINARY POINT TEMPS/POPS
KEY WEST 91 80 90 78 / 40 40 60 70
MARATHON 89 79 89 78 / 40 40 60 70
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...NONE.
PUBLIC/MARINE/FIRE...MJV
AVIATION/NOWCASTS....MJV
DATA ACQUISITION.....AJP
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