Marine Weather and Tide Forecast for Big Coppitt Key, FL

DISCUSSION
Issued at 453 AM EDT Sun Apr 19 2026

Additional low level moisture has been slowly moving in across the Keys. Last night's sounding showed that layered moisture extends up to around 7000 feet, 2000 feet deeper than 24 hours ago.
Meanwhile, an upper level ridge across the Gulf has shifted equatorward into the northwestern Caribbean. This subtle shift has allowed for a little more vertical motion overnight than previously seen. Despite that, shower coverage remains isolated and limited to the coastal waters surrounding the Keys. Lastly, temperatures and dew points are on the muggy side this morning with current temps still in the upper 70s with dew points in the lower 70s.

For today, a surface high that has seemingly been unmovable will finally shift eastward across the Atlantic and loosen its grip on the Florida Keys. This will leave us in a col region, resulting in light and variable winds developing during the morning and afternoon today. This will be brief as a cold front currently draped across the North Gulf coast will be making slow but steady progress southward over the next 24 to 48 hours.

Said cold front will sweep through Monday evening with a blast of northeasterlies. Windy conditions will develop in earnest overnight Monday and continue through Wednesday. A little better moisture will also accompany the front and it will be enough for some scattered showers and possible a few thunderstorms. Given the north to northeast steering flow on Monday, the first areas to see thunderstorms will be the Upper Keys and surrounding coastal waters immediately downwind of the mainland. As the front sweeps through, the remainder of the Keys will see a chance of thunderstorms.

Our chance at rain and any accumulations will unfortunately be limited to Monday evening as the front moves through. GFS and ECMWF have both come into agreement that the moisture plume with the front will slide well to our south. There remains a signal on Thursday for another shot at some rain as a potent upper level shortwave pivots southeast across the Gulf and over the Keys.
However, this will remain highly dependent on how much moisture we can recover prior to that feature arriving. Otherwise, there are no other discernible features that will make a noticeable dent in our moderate drought conditions within the next 5 - 7 days.

MARINE
Issued at 453 AM EDT Sun Apr 19 2026

A surface high pressure across the central North Atlantic will pull further east away from the Florida Keys. This will result in a col region developing across most of our waters and allow for winds to go briefly light and variable later today. Meanwhile, a frontal boundary currently moving into the North Gulf states will be slowly shifting south over the next 24 to 48 hours. This will promote a wind surge to develop tonight along the west coast of Florida and spill into the waters mainly west of the Seven Mile Bridge. On Monday as the Mainland heats up we will see an attempt for breezes to slacken prior to the arrival of the front. However, confidence on timing and duration is too low to include a transition for breezes on Monday. Nonetheless, the front will sweep through Monday evening with a sharp freshening of breezes.
Expect fresh to strong northeasterlies to develop in earnest overnight Monday and continue through Wednesday. Breezes will peak Tuesday and we could see a brief period of strong to near- gale breezes. Moderate to fresh breezes will return by Thursday.

AVIATION
(06Z TAFS)
Issued at 453 AM EDT Sun Apr 19 2026

A brief passing MVFR CIG will be possible over the next few hours, otherwise expecting VFR conditions. East to southeast winds will decrease and may go light and variable at times this afternoon.
Expect a more decidedly wind shift from the north this evening.

KEY WATCHES/WARNINGS/ADVISORIES
FL...None.
GM...None.