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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