321  
FXUS62 KKEY 250228  
AFDKEY  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE KEY WEST FL  
1028 PM EDT THU SEP 24 2020  
   
DISCUSSION
 
 
THE MOST IMPACTFUL SHORT-TERM ISSUE WILL AGAIN BE SALTWATER  
FLOODING ON FRIDAY MORNING. THE DIFFERENCE BETWEEN TIDE TABLE  
PREDICTIONS AND OBSERVED TIDE LEVELS IS RUNNING AROUND AN  
UNCOMMONLY HIGH 1.3 FEET AT KEY WEST. GIVEN THIS TREND, TIDES WILL  
PEAK ON FRIDAY MORNING AT LEVELS SIMILAR TO EARLY THIS MORNING.  
HIGH WATER WILL BE MOST NOTICEABLE FROM ABOUT 4-9 AM, WITH AREAS  
OF STANDING WATER LINGERING FOR A FEW HOURS AFTER THE TIDE FALLS.  
A COASTAL FLOOD ADVISORY IS IN EFFECT FOR THE ENTIRE KEYS UNTIL 12  
NOON.  
 
OUR 1000-700 MB LAYER FLOW HAS TURNED SOUTHERLY OVER THE PAST 24  
HOURS, THANKS IN PART TO THE NORTHEAST MOVEMENT OF POST-TROPICAL  
CYCLONE BETA ACROSS WEST-CENTRAL AND NORTHERN ALABAMA THIS  
EVENING. THE TURN TO SOUTHERLY FLOW WIPED OUT YESTERDAY'S DRY AIR  
MASS IMPRESSIVELY QUICK. SINCE LAST EVENING, THE 00Z KEY SOUNDING  
SHOWED AN INCREASE IN PW VALUES FROM 1.47" TO 2.4".  
 
AGAINST THE BACKDROP OF RICH AND DEEP MOISTURE, A SMALL-SCALE  
TROUGH IS LIFTING NORTH ACROSS THE KEYS. THIS IS ADDING LIFT TO  
THE VERY MOIST AND MODERATELY UNSTABLE AIR MASS. LATER FRIDAY,  
THAT TROUGH WILL MOVE NORTHWARD TO CENTRAL FLORIDA. SO WE WILL  
LOSE THE LARGER-SCALE LIFT BY FRIDAY EVENING. LIGHT AND VARIABLE  
LOW-LEVEL FLOW OVER THE WEEKEND WILL LET DIFFERENTIAL HEATING AND  
CONVECTIVE OUTFLOWS BE THE MAIN DRIVER OF CONVECTIVE DEVELOPMENT.  
LOW CHANCE POPS WILL COVER THE WEEKEND WEATHER NICELY.  
 

 
   
MARINE
 
 
WINDS WILL GRADUALLY VEER FROM SOUTHEAST TO SOUTH OVERNIGHT, AS A  
NORTHWARD-MOVING TROUGH CROSS THE WATERS.  
 
PRESSURE GRADIENTS WILL BECOME QUITE WEAK FROM FRIDAY NIGHT  
THROUGH THE WEEKEND, LEAVING LIGHT AND VARIABLE WINDS OVER THE  
KEYS WATERS.  
 

 
   
AVIATION
 
 
VFR CONDITIONS WILL PREVAIL AT THE KEY WEST AND MARATHON TERMINALS.  
A FEW SHOWERS AND AN ISOLATED THUNDERSTORM ARE LIKELY TONIGHT  
THROUGH TOMORROW MORNING AS STORMS MOVE THROUGH THE ISLAND CHAIN  
WITH THE SOUTHERLY FLOW. BRIEF SUB VFR CONDITIONS ARE LIKELY  
DURING THE PASSAGE OF THESE STORMS. DRIER WEATHER IS EXPECTED  
STARTING TOMORROW AFTERNOON. WINDS SE-S 5 TO 10 KNOTS WITH  
OCCASIONAL GUSTS TO 20 KNOTS, ESPECIALLY DURING THE STRONGER  
STORMS.  
 

 
   
KEY WATCHES/WARNINGS/ADVISORIES
 
 
FL...COASTAL FLOOD ADVISORY UNTIL NOON EDT FRIDAY FOR FLZ076>078.  
 
GM...NONE.  

 
 

 
 
PUBLIC/MARINE/FIRE...HANER  
AVIATION/NOWCASTS....SDR  
DATA ACQUISITION.....DR/WLC  
 
VISIT US ON THE WEB AT WEATHER.GOV/KEY  
 
FOLLOW US ON FACEBOOK AND TWITTER AT:  
WWW.FACEBOOK.COM/NWSKEYWEST  
WWW.TWITTER.COM/NWSKEYWEST  
 
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