165  
FXUS62 KKEY 200140  
AFDKEY  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE KEY WEST FL  
940 PM EDT TUE MAR 19 2019  
   
DISCUSSION
 
 
AFTER A LULL IN THE PRECIP ACTIVITY ACROSS THE KEYS DURING THE  
LATE AFTERNOON HOURS, STRATIFORM RAIN COVERAGE AND EMBEDDED SHOWER  
COVERAGE HAS INCREASED ONCE AGAIN DURING THE MID EVENING, ALTHOUGH  
MOST OF THE RAINFALL REMAINS LIGHT AT THIS TIME. SKIES ARE CLOUDY  
OVER THE KEYS, WITH TEMPERATURES MOSTLY IN THE LOWER 70S, AND  
WINDS ON LAND FROM THE NORTHEAST AT 15 TO 20 MPH. SURFACE ANALYSIS  
INDICATES THAT A WEAK LOW PRESSURE AREA IS LIKELY LOCATED NEAR THE  
NORTHWEST COAST OF CUBA, WHILE WATER VAPOR SATELLITE IMAGERY SHOWS  
ONE MORE DISTURBANCE MOVING EASTWARD ACROSS THE SOUTHEASTERN GULF,  
WITH A MUCH DRIER AIRMASS FILLING INTO THE CENTRAL GULF BEHIND  
THIS FEATURE. THE 00Z KEY WEST SOUNDING REMAINED VERY MOIST WITH  
PW OF 1.74 INCHES, WHICH IS WELL ABOVE THE 90TH PERCENTILE FOR  
THIS DATE.  
 
IN THE SHORT TERM, EXPECT MOSTLY STRATIFORM LIGHT TO MODERATE  
RAIN TO CONTINUE ACROSS THE KEYS FOR THE REST OF THE EVENING. AN  
ISOLATED EMBEDDED HEAVIER SHOWER OR EVEN A THUNDERSTORM CANNOT BE  
RULED OUT OVER THE ISLAND CHAIN, BUT IT IS MORE LIKELY THAT ANY  
THUNDERSTORMS WILL REMAIN OVER THE STRAITS AND SOUTH OF THE KEYS.  
AS THE DISTURBANCE CURRENTLY IN THE SE GULF MOVES QUICKLY EASTWARD  
ACROSS THE KEYS LATE TONIGHT, SHOWER ACTIVITY SHOULD TAPER OFF  
OVER THE KEYS AND GULF WATERS AS THE PRIMARY AREA OF DEEP MOISTURE  
AND LIFT SHIFTS SE INTO THE EASTERN STRAITS. OTHERWISE, WINDY  
CONDITIONS SHOULD ALSO TAPER OFF LATE TONIGHT, AND LOW TEMPS  
SHOULD DROP ONLY A FEW DEGREES INTO THE UPPER 60S. THE PUBLIC  
FORECASTS HAVE BEEN UPDATED TO REFLECT THE ABOVE THINKING.  
 
A MUCH DRIER PATTERN REMAINS ON TRACK FOR THE KEYS BEGINNING  
WEDNESDAY, WITH RAIN CHANCES TAPERING OFF TO SLIGHT, THEN NONE BY  
THURSDAY AFTERNOON. EXPECT MOSTLY CLEAR, DRY AND SEASONABLE  
WEATHER FOR THURSDAY THROUGH SATURDAY, WITH HIGHS IN THE UPPER 70S  
TO NEAR 80 AND LOWS IN THE MID 60S TO NEAR 70. SCATTERED SHOWERS  
MAY RETURN TO THE AREA BEGINNING SUNDAY AND CONTINUING INTO EARLY  
NEXT WEEK, BUT RECENT MODEL GUIDANCE HAS TRENDED DRIER, AND LATER  
SHIFTS MAY REDUCE RAIN CHANCES FOR THOSE PERIODS.  
 

 
   
MARINE
 
 
NE WINDS HAVE GRADUALLY DECREASED ACROSS MUCH OF THE KEYS COASTAL  
WATERS DURING THE EVENING, BUT RECENTLY SURGED BACK UP TO 27 KNOTS  
SUSTAINED AT PULASKI SHOAL LIGHT. THIS MAY BE DUE TO THE LOW  
PRESSURE AREA PASSING TO THE SOUTH OF THE WESTERN STRAITS AT THIS  
TIME. WINDS ARE CURRENTLY RUNNING BELOW 20 KNOTS AT MOST OF THE  
OTHER REPORTING SITES, BUT SHORT-RANGE MODEL GUIDANCE SUGGESTS  
THAT WINDS WILL SURGE BACK UP ABOVE 20 KNOTS ACROSS MUCH OF THE  
MARINE AREA DURING THE NEXT SEVERAL HOURS AS THE LOW PASSES TO OUR  
SOUTH. WILL MAINTAIN THE SMALL CRAFT ADVISORY FOR ALL ZONES WITH  
THE LATE EVENING FORECAST ISSUANCE. WE DO EXPECT WINDS TO BEGIN  
DECREASING TOWARD MORNING, AND TO CONTINUE DROPPING ON WEDNESDAY.  
 

 
   
AVIATION
 
 
LARGE AREA OF LIGHT TO MODERATE STRATIFORM RAIN WILL SPREAD  
ACROSS THE TERMINALS FOR THE REST OF THIS EVENING. HEAVIEST RAIN  
WITH LOWEST CIGS/VSBYS WILL COME LATER THIS EVENING IN THE 02Z-  
05Z TIME FRAME. DURING THAT TIME, CIGS BELOW 010 AND VSBYS IN THE  
4- 6SM RANGE ARE POSSIBLE, AS INDICATED IN GFS STATISTICAL  
GUIDANCE. HEAVIER RAIN SHOULD THEN TAPER OFF TO SHOWERS BEFORE  
MIDNIGHT. THE BOUNDARY LAYER WILL REMAIN RICHLY MOIST INTO WED  
MORNING, WITH GFS LAMP GUIDANCE CARRYING MVFR CIGS IN THE 010-020  
RANGE UNTIL 17Z AT EYW. HAVE ONLY SHAVED THIS EXPECTATION A LITTLE  
WITH SCATTERING INDICATED AT 16Z (NOON) IN THE TAFS. THE HRRR  
EVEN SHOWS CIGS HOVERING JUST BELOW 010 ON A TEMPORARY BASIS AS  
LATE AS 14Z-15Z ON WED MORNING. EXPECT RAPID SCATTERING AND  
LIFTING OF CLOUD BASES AFTER ABOUT 16Z TO 17Z.  
 

 
   
CLIMATE
 
 
ON THIS DATE IN FLORIDA KEYS WEATHER HISTORY, IN 2003, THE LOW  
TEMPERATURES AT KEY WEST (78F) AND MARATHON (79F) WERE BOTH WARMER  
THAN THE HIGH TEMPERATURES RECORDED TODAY. THE HIGH AT KEY WEST  
TODAY WAS 75F AND AT MARATHON IT WAS 77F.  
 
THE LOW AT MARATHON ON MARCH 19TH, 2003 WAS THE FIRST OF 3 DAYS  
IN A ROW WITH A LOW TEMPERATURE OF 79F, TYING AS THE WARMEST LOW  
TEMPERATURE EVER RECORDED IN THE MONTH OF MARCH.  
 

 
   
KEY WATCHES/WARNINGS/ADVISORIES
 
 
FL...NONE.  
GM...SMALL CRAFT ADVISORY FOR GMZ031>035-042>044-052>055-072>075.  
 

 
 

 
 
PUBLIC/MARINE........JACOBSON  
AVIATION/NOWCASTS....HANER  
DATA COLLECTION......DR  
 
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