Marine Weather Net

Florida Bay including Blackwater and Buttonwood Sounds Marine Forecast


TONIGHT

W
WINDS
15 - 20
KNOTS

TUESDAY

N
WINDS
20 - 25
KNOTS

TUESDAY NIGHT

NNE
WINDS
20
KNOTS

WEDNESDAY

NE
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
GMZ031 Forecast Issued: 335 PM EST Mon Nov 30 2020

SMALL CRAFT ADVISORY IN EFFECT
Tonight...West Winds 15 To 20 Knots, Becoming Northwest To North And Increasing To 20 To 25 Knots. Bay Waters Choppy, Becoming Very Rough. Widespread Showers And Isolated Thunderstorms In The Evening, Then Scattered Showers After Midnight.
Tuesday...North Winds 20 To 25 Knots, Decreasing To 15 To 20 Knots Late In The Afternoon. Bay Waters Very Rough, Becoming Choppy.
Tuesday Night...North To Northeast Winds Near 20 Knots. Bay Waters Rough.
Wednesday...Northeast Winds 15 To 20 Knots. Bay Waters Choppy.
Wednesday Night...Northeast To East Winds 15 To 20 Knots. Bay Waters Choppy.
Thursday...East Winds Near 15 Knots. Bay Waters A Moderate Chop.
Thursday Night...East Winds Near 15 Knots. Bay Waters A Moderate Chop. Isolated Showers.
Friday...East To Southeast Winds Decreasing To 10 To 15 Knots. Bay Waters Becoming A Light To Moderate Chop. Scattered Showers.
Friday Night...East To Southeast Winds Near 10 Knots. Bay Waters A Light Chop. Scattered Showers.
Saturday...Winds Becoming Northwest To North 5 To 10 Knots. Bay Waters Smooth To A Light Chop. Scattered Showers.
Saturday Night...Northwest To North Winds Near 15 Knots. Bay Waters A Moderate Chop. Isolated Showers.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
335 PM EST Mon Nov 30 2020

A vigorous cold front will sweep quickly through the coastal waters of the Florida Keys this evening. Behind the cold front, strong northerly breezes will persist into Tuesday morning. Fresh to strong northeast to east breezes will persist from Tuesday through at least Thursday night. Breezes will diminish Friday and Friday night, and may freshen from the northwest as early as Saturday afternoon.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of November 28...
- 48 NM South of Dry Tortugas Light...on Loggerhead Key.
- 45 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 28 NM South of Sand Key Light...off Key West.
- 7 NM South of Looe Key...off Big Pine Key.
- 1 NM South of Sombrero Key Light...off Marathon.
- 1 NM Southeast of Alligator Reef Light...off Islamorada.
- 1 NM Southeast of Molasses Reef Light...off Key Largo.
- 1 NM East of Carysfort Reef Light...off Ocean Reef.
Area Forecast Discussion
National Weather Service Key West FL
355pm EST Monday Nov 30 2020

Water vapor imagery highligheights a potent long-wave trough across the eastern United States, maintaining a powerful surface cyclone moving northeast through the northern Appalachians. The cold front associated with this system is nearly on our doorstep, and will press into the Dry Tortugas in the next hour or so. Warm air advection and pre-frontal troughiness has been across the Keys most of the day, with extensive cloud cover, patches of stratiform rains, and a few discrete showers. Linear forcing along the front has maintained a broken swath of persistent rains, although convergence into this line is limited with winds veered to the west ahead of the line. The main forecast conundrum throughout the day has been the strength of the winds, much stronger than expected, but not in the usual spots. Normally, locations adjacent to South Florida will accelerate ahead of a frontal passage, instead, locations like Sand Key and Smith Shoal have been screaming for the last several hours.

.FORECAST... Mean-layer streamlines are nearly parallel to the frontal boundary, so the line of rains just to the northwest of the Dry Tortugas may take a while to get here this evening. If winds can back to the southwest ahead of this line, then more intense convection would form along this line. By midnight tonight, northwest to north breezes will freshen appreciably across the island chain, driving cooler and drier air through the Keys. The Gulf and Bayside water temperatures are in the mid to upper 70s, so lows Tuesday morning will be tempered, although everyone should fall well into the 60s. Temperatures on Tuesday will struggle to break through 70 with dewpoints falling into the upper 40s Tuesday evening. The coldest air of the season will be Wednesday morning with portions of the Middle and Upper Keys in the mid to upper 50s, and Key West trying to fall through 60.

Winds will veer steadily from the northeast to east, Wednesday through Thursday night, although the cooler nearshore waters north of the island chain will retain a mesoscale component from the northeast. The forecast for Friday and beyond is of low confidence. The future evolution of a surface trough over the Gulf of Mexico will modulate the sensible weather elements through the weekend. We could see a warm frontal feature come through on Thursday night through Friday night, with rain chances becoming likely. However, some of the global models keep the Keys mostly dry late tonight through the extended forecast. For now, we went with a blend in Probability of Precipitation through the extended with a portrayed second frontal passage Saturday night. However, this may be well delayed.

Marine
Small Craft Advisory in effect for all coastal waters of the Florida Keys due to strong northwest to north breezes. From synopsis, a vigorous cold front will sweep quickly through the coastal waters of the Florida Keys this evening. Behind the cold front, strong northerly breezes will persist into Tuesday morning. Fresh to strong northeast to east breezes will persist from Tuesday through at least Thursday night. Breezes will diminish Friday and Friday night, and may freshen from the northwest as early as Saturday afternoon.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...Small Craft Advisory for GMZ031>035- 042>044-052>055-072>075.