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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
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