Marine Weather and Tide Forecast for Big Pine Key, FL

DISCUSSION
Issued at 1036 AM EST Sat Nov 29 2025

We continue to see windy conditions across the Florida Keys this morning. Across the marine platforms we are observing 20 to 25 knots with the Florida Bay being the only exception this morning at near 15 knots. These winds remain elevated due to the proximity of the cold front that passed through the other day. It has now begun lifting back northward as a warm front and the pressure gradient along this baroclinic zone remains tightened. This is also allowing for moisture to surge and pool along and behind the leading edge of this warm front. For now we've only observed fast moving showers but as the front gets closer to the area we could see embedded isolated thunderstorms develop.

Made only minor adjustments to the winds to account for the slower transition this morning, while still keeping the same magnitude for this afternoon. Rain chances were left alone for now with the highest chances out across the Straits of Florida.

MARINE
Issued at 1036 AM EST Sat Nov 29 2025

A frontal boundary south of the area, paired with a dominant surface high over the eastern CONUS, will maintain fresh to strong northeasterly breezes this afternoon, and Small Craft Advisories will likely extend through tonight. As the front decays and the high shifts northeastward, breezes will begin to slacken by early Sunday. Another cold front may be on the horizon for the middle of the week, reflected in the breezes turning around the clock ahead of it. Shower activity will wax and wane throughout the marine forecast period.

AVIATION
(15Z TAFS)
Issued at 1036 AM EST Sat Nov 29 2025

VFR conditions are expected outside of any quick moving rain shower this morning. As we progress into the afternoon, instability will increase and could support a few isolated thunderstorms. Timing and exact location is limiting the use of VCTS at this time. Otherwise, near surface winds of east-northeast near 20 knots, gusting higher at times will prevail through the afternoon and early evening.

PREV DISCUSSION
Issued at 427 AM EST Sat Nov 29 2025

The cool snap continues across the Florida Keys early this morning. Temperatures along the Island Chain have been quite steady overnight remaining in the mid 60s with dew points in the lower 60s. The cool temperatures are being met with a consistent breeze giving it the Florida winter chill to the air. Strong surface high pressure is centered over the Appalachian Mountains of Virginia and West Virginia. This continues to promote moderate to fresh northeast to east breezes at marine platforms surrounding the Island Chain. Gentle to moderate breezes prevail at communities along the Island Chain. GOES East Nighttime Microphysics imagery shows most of the cloud cover remaining over the marine waters to the south and west of the Island Chain with KBYX radar not detecting any showers associated with these clouds.


FORECAST
The forecast for the next several days will be dominated by a series of high pressure systems traversing across the eastern United States. This will keep a healthy pressure gradient across the area resulting in moderate to fresh northeast breezes this morning strengthening to fresh to strong northeast to east breezes for this afternoon and evening. The cold front that moved through yesterday will start to move back to the northwest as a warm front shifting breezes to the northeast to east. Also, looking at GOES Total Precipitable Water (TPW) products, the leading edge to much moister air is loitering just outside of the Keys coverage area where PWAT values of 1.4 to 1.7 inches are being estimated compared to 0.7 to 1 inch currently over the Keys.
Since we have a moisture, wind, and instability surge waiting in the wings, there will no doubt be an expected increase in shower activity across the area later this afternoon and evening.
Therefore, timing was introduced to the forecast keeping slight chances in this morning for the Island Chain with chances for the afternoon and tonight. All the ingredients are coming together for an active afternoon and evening. Most of this shower activity will be driven by speed convergence across the area with some directional convergence. Add in the instability to this and now these collisions can lead to potential for thunderstorms in a ripened moist environment, especially over the Straits.

Breezes will begin to dramatically slacken overnight Saturday into Sunday. Another high will move across the eastern United States taking the place of the previous high, though, this one won't be as strong. Therefore, expect mainly gentle to moderate northeast to east breezes to continue through Monday evening before shifting to the east to southeast and further slackening overnight through Tuesday night. Moisture will remain with the main catalyst for showers being driven by mostly speed or directional convergence and other mesoscale processes or remnant boundaries.

Another frontal boundary is expected to approach the Keys mid to late week due to a developing coastal low off the Carolina coast.
However, before the front approaches, there may be a time frame where the winds go light and variable along with dew points climbing into the lower to mid 70s due to the southeast to south breezes pumping up the dew points. Observations in Florida Bay would suggest SST's in the mid to upper 60s. If the dew points are able to get close to this along with light and variable wind flow, there may be a window of time for sea fog to develop. We continue to keep an eye on this. The details still remain murky in regards to the front. Some guidance pushes this front through and others stall it right over the Keys. Details will become clearer in the coming days. Stay tuned!



PRELIMINARY POINT TEMPS/POPS
Key West 77 72 79 74 / 40 50 20 10 Marathon 77 73 80 73 / 40 50 20 20

KEY WATCHES/WARNINGS/ADVISORIES
FL...None.
GM...Small Craft Advisory for GMZ031>035-042>044-052>055-072>075.