405
FXUS62 KKEY 202019
AFDKEY
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
319 PM EST SUN JAN 20 2019
SHORT TERM
IN THE WAKE OF THIS MORNING'S FRONT, STRONG NORTHWEST WINDS HAVE
KICKED IN, WITH EYW RECENTLY GUSTING NEAR 35 MPH. SOME COLD AIR
STRATO-CUMULUS HAS SPREAD IN BEHIND THE FRONT, BUT SKIES WILL
CLEAR OUT TONIGHT AS LOW-LEVEL WINDS VEER AND COME OFF THE FLORIDA
PENINSULA TONIGHT. A DRY AIR MASS WILL SPREAD OVER THE KEYS,
SUPPORTING LOW TEMPERATURES IN THE 50S THROUGHOUT THE ISLAND
CHAIN AROUND SUNRISE ON MONDAY.
WINDS WILL WASTE NO TIME CLOCKING AROUND OUT OF THE NORTHEAST ON
MONDAY MORNING, AS A STRONG SURFACE HIGH PRESSURE CENTER MOVES UP
THE OHIO VALLEY. BY TUE, THE HIGH CENTER WILL CONSOLIDATE INTO A
1037 MB JUST OFFSHORE THE NC OUTER BANKS. STRONG GRADIENTS ON ITS
SOUTHERN PERIPHERY WILL REALLY CAUSE EASTERLY SURFACE WINDS TO
PICK UP OVER THE KEYS, BECOMING BREEZY OR WINDY. PEAK LAND-BASED
WIND GUSTS OF 25-30 MPH ARE LIKELY ON TUE PM. WITH SUCH STRONG
EASTERLY RETURN FLOW, DEWPOINTS WILL RECOVER THROUGH THE 50S ON
MONDAY NIGHT AND HIT THE 60S ON TUE, THEN REACH NEAR 70F ON WED.
SURFACE-BASED MOISTURE WILL DEEPEN ABOVE 850 MB ON TUE AM. PW
VALUES WILL RISE ABOVE 1" ON TUE EVENING, THEN ABOVE 1.5" ON WED.
WITH STEADILY INCREASING MOISTURE, ISOLATED TO SCATTERED SHOWERS
OVER THE WATERS WILL START TO SPREAD IN FROM THE GULF STREAM,
ESPECIALLY FROM LATE TUE THROUGH WED.
LONG TERM
THE NEXT COLD FRONT IS EXPECTED ON THURSDAY. PW VALUES WILL PEAK
IN EXCESS OF 1.75", AND THE AIR MASS PRECEDING THE FRONT WILL BE
MODERATELY UNSTABLE. SO HAVE HIGH POPS, INCLUDING A CHANCE OF
THUNDERSTORMS CENTERED ON THURSDAY.
THE FRONT WILL SLOWLY PUSH SOUTHEAST OF THE KEYS ON FRIDAY, WITH A
STEADY DRYING TREND FORECAST THROUGH SATURDAY.
HOWEVER, CONSIDERABLE SPREAD DEVELOPS NEXT SATURDAY AND SUNDAY
AMONGST SOLUTIONS IN BOTH THE GLOBAL MODELS AND GFS ENSEMBLE
MEMBERS. WHAT THEY AGREE ON IS A HIGH AMPLITUDE AND DEEP UPPER
TROUGH DEVELOPING OVER THE MISSISSIPPI VALLEY, WITH NEGATIVE
HEIGHT ANOMALIES AND WEST-SOUTHWEST FLOW ALOFT OVER THE KEYS. THE
12Z DETERMINISTIC ECMWF BRINGS THE FRONT BACK NORTH OVER THE KEYS
ON SATURDAY, LOOKING QUITE WET. THE 12Z GFS APPEARS TO BE AN
OUTLIER NEXT WEEKEND WITH HOW COOL AND DRY THE WEATHER GETS, BUT
ONLY ABOUT 4-6 OF ITS 20 ENSEMBLE MEMBERS ARE SHOWING RAIN NEXT
WEEKEND. HOWEVER, THE ENSEMBLES THAT DO SHOW RAIN ARE QUITE WET.
SO HAVE BROUGHT SLIGHT CHANCE POPS INTO THE FORECAST STARTING
SATURDAY NIGHT, BUT THERE IS PROBABLY ROOM TO RAISE POPS FURTHER
AS A REFLECTION OF FORECAST UNCERTAINTY.
MARINE
STRONG NORTHWEST WINDS ARE BLOWING ACROSS ALL THE WATERS BEHIND
THIS MORNING'S COLD FRONT, WITH SOLID 25-KNOT NORTHWESTERLIES.
UPSTREAM OF THE KEYS, SEAS AT THE PULLEY RIDGE BUOY PEAKED AT 12
FEET AT 1 PM. OVER OUR WATERS, SEAS IN EXCESS OF 10 FEET ARE
LIKELY OCCURRING RIGHT NOW OVER THE DEEP WATERS OF THE SOUTHEAST
GULF AND THE WATERS OF THE STRAITS SOUTH OF THE DRY TORTUGAS.
THE PATTERN WILL SHIFT QUICKLY ON MONDAY AND TUESDAY, AS A STRONG
SURFACE HIGH OVER THE OHIO VALLEY ON MONDAY CONSOLIDATES NEAR THE
OUTER BANKS ON TUESDAY AS A 1037 MB HIGH. SO THE LULL IN WIND OVER
THE WATERS WILL BE QUITE SHORT, CONFINED TO A PERIOD OF MODERATE
NORTHEAST BREEZES AROUND LUNCHTIME ON MONDAY. THEN WINDS WILL
CLOCK AROUND OUT OF THE EAST AND START TO INCREASE QUICKLY LATER
IN THE DAY. STRONG E-SE WINDS ARE EXPECTED ON TUESDAY OVER ALL
WATERS. AT THE PEAK OF EAST WINDS, THE 12Z GFS MARINE MOS VALUES
ON TUE PM RANGE FROM 22 KNOTS AT LONG KEY TO 30 KNOTS AT SAND
KEY.
THE NEXT COLD FRONT IS EXPECTED THURSDAY. IT WILL BE PRECEDED BY
A TURN TO MODERATE AND FRESH SOUTHERLIES ON WED NIGHT. LOOKS LIKE
ANOTHER LINE OF THUNDERSTORMS IMMEDIATELY PRECEDING THE FRONT,
THEN A TURN TO MODERATE NORTHERLY BREEZES WHICH WILL FRESHEN
ON FRIDAY.
AVIATION
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH TONIGHT AT EYW AND
MTH. OCCASIONAL CEILINGS JUST ABOVE FL030 TO FL035 ARE EXPECTED
THROUGH AT LEAST 06Z, BEFORE GRADUAL CLEARING. SURFACE WINDS WILL BE
OUT OF THE NORTHWEST SUSTAINED 14 TO 18 KNOTS WITH FREQUENT GUSTS
NEAR 25 KNOTS THROUGH EVENING, THEN BECOMING NORTHERLY OUT OF 330-
360 DEGREES AFTER 21/03Z. WINDS ARE EXPECTED TO QUICKLY VEER TO 360-
030 DEGREES NEAR AND AFTER 21/12Z WITH SLIGHT DECREASE IN SPEEDS.
KEY WATCHES/WARNINGS/ADVISORIES
FL...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 5 AM EST MONDAY FOR GMZ031>035-
042>044-052>055-072>075.
PUBLIC/MARINE/FIRE...HANER
AVIATION/NOWCASTS....JR
DATA COLLECTION......DR
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