Straits of Florida from Craig Key to West End of Seven Mile Bridge out 20 - 60 NM Marine Forecast
|This Afternoon...South Winds Near 15 Knots, Becoming South To Southwest And Decreasing To Near 10 Knots. Seas 3 To 5 Feet, Subsiding To 2 To 3 Feet. Scattered Showers And Isolated Thunderstorms Developing Late In The Afternoon. Winds And Seas Higher Near Thunderstorms.|
|Tonight...South To Southwest Winds Near 10 Knots. Seas 1 To 2 Feet. Numerous Showers And Scattered Thunderstorms In The Evening, Then Scattered Showers And Isolated Thunderstorms After Midnight. Winds And Seas Higher Near Thunderstorms, Especially In The Evening.|
|Monday...Southwest To West Winds 10 To 15 Knots, Becoming West To Northwest During The Afternoon. Seas 1 To 2 Feet. Scattered Showers And Isolated Thunderstorms.|
|Monday Night...Northwest Winds 10 To 15 Knots, Becoming Northeast To East And Increasing To Near 15 Knots. Seas Building To 2 To 4 Feet. Isolated Showers.|
|Tuesday...East Winds 10 To 15 Knots. Seas 2 To 4 Feet.|
|Tuesday Night...East Winds 10 To 15 Knots. Seas 2 To 4 Feet.|
|Wednesday...East To Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet.|
|Wednesday Night...Southeast Winds Decreasing To 5 To 10 Knots. Seas Subsiding To 1 To 2 Feet.|
|Thursday...South Winds Near 5 Knots Becoming West To Northwest In The Afternoon. Seas Around 1 Foot.|
|Thursday Night...Northwest Winds 5 To 10 Knots. Seas Around 1 Foot.|
| Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005|
1033 AM EDT Sun Apr 11 2021
High pressure over the western Atlantic will retreat further offshore this afternoon and tonight, as a low pressure trough moves through the Florida peninsula. Gentle to moderate southerly breezes will become south to southwest and slacken to light to gentle into the afternoon. Unsettled weather is expected late this afternoon and tonight, with the potential for a significant squall line to move southward through the Keys waters during the evening hours. A very weak front will ease into the Keys Monday night, briefly swinging winds around the compass, before settling to gentle to moderate easterly flow by Tuesday. Light to gentle breezes are forecast for the middle and later part of the week.
The Approximate Shoreward Edge of the Gulf Stream as of April 10...
- 57 NM South of Dry Tortugas Light...on Loggerhead Key.
- 12 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 5 NM South of Sand Key Light...off Key West.
- 6 NM South of Looe Key...off Big Pine Key.
- 6 NM South of Sombrero Key Light...off Marathon.
- 10 NM Southeast of Alligator Reef Light...off Islamorada.
- 2 NM Southeast of Molasses Reef Light...off Key Largo.
- 2 NM East of Carysfort Reef Light...off Ocean Reef.
| Area Forecast Discussion|
National Weather Service Key West FL
1104am EDT Sunday April 11 2021
Currently - It's the calm before the storm this morning. Overnight activity has long since diminished and dissipated. It was quite an impressive, yet decaying squall line that came through overnight. Strongest winds were reported at Long Key C-MAN station which registered a 42 knot, or 48 mph wind gust.
Today so far, we've had fair weather cu and strato-cu streaming in from the south. We have more low level moisture today than this time yesterday. Yesterday there was hardly a cloud in the sky and today they are proliferating. Taking a look at this morning's 12Z RAOB (Radiosonde Observation or Upper-Air Observation) we have a PWAT (Precipitable Water) of 1.52 compared to 1.24 inches 24 hours ago. As a side note, this PWAT (Precipitable Water) value places it between the 75th and 90th percentile. Instability is also definitely higher today with a MLCAPE of close to 2000 J/kg. Meanwhile, cu is developing a lot sooner over Cuba this morning and starting to look agitated.
I mention all of this because another squall line/MCS is currently across the eastern Gulf of Mexico and sliding southeast towards our area. The atmosphere is better primed today for strong to marginally severe weather later this afternoon and evening. Convective allowing models (CAMs) are showing this squall line/MCS shifting southeast towards our area, arriving in the late afternoon at the earliest. At the same time, CAMs are hinting at boundaries being ejected from Cuba in the late afternoon ahead of this squall line. The difference in today vs yesterday is the upper level trough associated with this surface feature will pass relatively close to our area. Yesterday's line was far removed from the upper level support by the time it reached us. With that said, we will still be slightly displaced from the main upper level forcing and therefore coverage and intensity will be limited. Best chances may favor the Upper Keys with the initial convection and then slide south across the Middle and Lower Keys. However, will maintain likely chances for the evening and taper back to chances after midnight. Any thunderstorms that push across the area will have a wind threat as the main impact.
Thereafter, we may have a reverse cloud line situation for Monday but otherwise, generally dry conditions will return towards midweek.
Generally moderate southerly breezes prevail across all waters this morning. Winds should slacken and become more southwest by this afternoon. Continuing to monitor for inclement weather as a line of strong showers and thunderstorms are sliding southeast across the eastern Gulf of Mexico and Florida Peninsula. Current timing would arrive in our waters by the late afternoon and early evening. The main threat would be strong gusty winds and higher seas in the vicinity of thunderstorms.
From synopsis: A very weak front will ease into the Keys Monday night, briefly swinging winds around the compass, before settling to gentle to moderate easterly flow by Tuesday. Light to gentle breezes are forecast for the middle and later part of the week.
NOAA Key West FL Office: Watches - Warnings - Advisories