Sounds like a powerful front is moving through. It is still pretty far off to guarantee the Lower Keys forecast shown below*, could be weaker, a bit stronger or spot on at this distant point. If the front is delayed, would advise getting out as early on Friday as feasible. I would check for Key West updates at:
Coastal Waters Forecast for Coastal waters from the west end of the 7 Mile Bridge to Key West out 20 NM (GMZ054)
and for Ft. Lauderdale at:
Coastal Waters Forecast for Coastal waters from Deerfield Beach to Ocean Reef FL out 20 NM (AMZ651)
Still more resources at:
Weather Resources For SE Florida - FKA Kiteboarding Forums
Hope things workout for your visit
As time goes on, the forecast and actual conditions will likely change to a degree.
Thursday...East winds 10 to 15 knots. Seas beyond the reef 2 to 4 feet. Seas higher in the gulf stream. Seas inside the reef 1 to 2 feet. Nearshore waters a moderate chop. Scattered showers developing.
Thursday Night...Southeast winds near 15 knots and gusty. Seas beyond the reef 3 to 5 feet. Seas inside the reef around 2 feet. Nearshore waters a moderate chop. Scattered showers and thunderstorms.
Friday...South to southwest winds 15 to 20 knots...increasing to near 20 knots and gusty. Seas beyond the reef building to 5 to 7 feet. Seas inside the reef building to 2 to 3 feet. Nearshore waters becoming rough. Showers and thunderstorms.
Friday Night...Winds becoming west to northwest 20 to 25 knots. Seas beyond the reef 4 to 7 feet. Seas inside the reef 2 to 3 feet. Nearshore waters rough. Showers and thunderstorms.
Saturday...Northwest winds 20 to 25 knots. Seas beyond the reef 5 to 8 feet. Seas inside the reef 2 to 4 feet. Nearshore waters rough. Isolated showers.
Sunday...Northwest to north winds near 20 knots. Seas beyond the reef 4 to 7 feet. Seas inside the reef 2 to 3 feet. Nearshore waters rough.
Monday...North winds 15 to 20 knots. Seas beyond the reef 3 to 6 feet. Seas higher in the gulf stream. Seas inside the reef around 2 feet. Nearshore waters choppy.
I'm headed down to dive the Vandenburg this weekend and then I'm moving up to FLL on Monday and Tuesday. I see it's supposed to be windy, rainy and cool. I also see they are forecasting seas 4-6 feet (building to 8-10). Hopefully I get to do some diving.