Marine Weather Net

Florida Bay including Blackwater and Buttonwood Sounds Marine Forecast


THIS AFTERNOON

SSE
WINDS
5 - 10
KNOTS

TONIGHT

NNW
WINDS
10 - 15
KNOTS

FRIDAY

NNE
WINDS
20 - 25
KNOTS

FRIDAY NIGHT

NE
WINDS
20
KNOTS

The Marine Weather Forecast In Detail:
GMZ031 Forecast Issued: 1017 AM EST Thu Nov 27 2025

SMALL CRAFT ADVISORY LIKELY WILL BE REQUIRED TONIGHT
This Afternoon...Southeast To South Winds 5 To 10 Knots, Becoming Northeast To East And Increasing To Near 10 Knots. Bay Waters Smooth To A Light Chop, Becoming A Light Chop. Scattered Showers And Isolated Thunderstorms.
Tonight...Northwest To North Winds 10 To 15 Knots, Becoming North And Increasing To 20 To 25 Knots Late. Bay Waters A Light To Moderate Chop, Becoming Very Rough. Scattered Showers.
Friday...North To Northeast Winds 20 To 25 Knots, Decreasing To Near 20 Knots. Bay Waters Very Rough, Becoming Rough. Isolated Showers.
Friday Night...Northeast Winds Near 20 Knots. Bay Waters Rough. Isolated Showers.
Saturday...Northeast To East Winds Near 20 Knots, Decreasing To 15 To 20 Knots. Bay Waters Rough, Becoming Choppy. Isolated Showers.
Saturday Night...Northeast To East Winds 15 To 20 Knots, Decreasing To 10 To 15 Knots. Bay Waters Choppy, Becoming A Light To Moderate Chop. Scattered Showers.
Sunday...East Winds 10 To 15 Knots, Decreasing To Near 10 Knots. Bay Waters A Light To Moderate Chop, Becoming A Light Chop. Scattered Showers.
Sunday Night And Monday...East Winds Near 10 Knots. Bay Waters A Light Chop. Isolated Showers.
Monday Night...East To Southeast Winds 5 To 10 Knots. Bay Waters Smooth To A Light Chop.
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Area Forecast Discussion
National Weather Service Key West FL
111pm EST Thu Nov 27 2025

Issued at 1020am EST Thu Nov 27 2025 Weather conditions are rather dynamic across the Keys this Thanksgiving morning. The combination of an approaching cold front over the Gulf, broad high pressure over eastern Cuba, and strong winds aloft are funneling deeper layers of moisture across the Keys. Scans from the KBYX radar show a mess of scattered showers over the western waters with measurable rainfall over the Lower Keys. Radar derived totals estimated almost half an inch of rainfall over parts of Lower Sugarloaf Keys with isolated points of nearly one inch of rainfall just south of Summerland Key. It should not be much of a surprise that the morning 12Z KKEy sounding sampled an environmental PWAT (Precipitable Water) that was just above the 90th percentile value for the day. However, the 675-300 mb layer was rather dry. Expect showers to cap below 20 kft for most of the day, and only a slight chance of thunderstorms was kept in the forecast.

The previously mentioned cold front is expected to move across the Keys this afternoon. Buoys north of the front, located west of Tampa, are sampling winds gusting to 21 knots. Winds will make a rapid transition from rather light to breezy pretty quickly after sunset. Dew points will also drop this evening, so dehumidifiers will receive a break later tonight. Current conditions, however, do not provide enough of a reason to change the forecast. Thanksgiving afternoon is on track to be humid with winds shifting to northerlies, off and on showers, and a very low chance of a stray thunderstorm. Check back tonight for updates on what the winds will be doing this weekend.

Marine
Issued at 505am EST Thu Nov 27 2025 There are no watches, warnings, or advisories in effect for the Florida Keys local waters, but Small Craft Advisories will likely be required tonight after a cold front pushes through. From synopsis, a weak pressure field across the area will encourage light to gentle east to southeast breezes early this afternoon, but a cold front pushing down the Florida peninsula will arrive to our marine zones late tonight. Breezes will back to the north and freshen quickly, and the lingering front will maintain fresh to strong breezes through the weekend. Small Craft Advisories will be needed by tonight, and will likely need to be extended through the end of the weekend. Breezes will gradually slacken over the beginning of next week. Shower activity will wax and wane throughout the marine forecast period.

.FORECAST... Issued at 505am EST Thu Nov 27 2025 We are in the middle of transitioning to a period of unsettled weather courtesy of an approaching cold front. GOES-19 IR imagery shows the cold front oriented southwest to northeast, and extending through the northern portion of the peninsula. Surface observations just north of the cold front are showing dew points in the lower 30s, a testament to the dry air associated with this front. The good news is that the front is still expected to pass across the Keys later tonight, so dinnertime festivities should not see too much excitement outside of the chance of showers we have today. None of us will be able to miss the arrival of the front as it dishes out breezy to windy conditions, but the drier air filtering in should help to clear out some of these showers. It is worth noting here that our local waters will likely see Small Craft Advisories as early as tonight due to the magnitude of these winds, and they will likely be needed through the end of the weekend. The northerly component to these low level winds will efficiently advect cooler air in, and overnight lows tonight are expected to bottom out in the mid 60s. Anyone acclimated to our usually beautiful weather may need to reach for a jacket in the early morning hours.

The progressive nature of this pattern will help to lift the remnants of the cold front away quickly, and the low level flow looks like it will shift from northerly to southeasterly. Long range guidance and ensemble members suggest a warm front nudging through sometime between Saturday night and Sunday night, bringing increased moisture and a better chance of showers. However, confidence with respect to the resulting sensible weather is relatively low since we haven’t cleared our Thanksgiving cold front yet.

Climate
In 1949, the daily record low temperature of 54F was recorded in Key West. Temperatures records for Key West date back to 1872. Also, in 1953, the daily record low temperature of 51F was recorded in Marathon. Temperature records for Marathon date back to 1950.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...None.