Marine Weather and Tide Forecast for Big Coppitt Key, FL

DISCUSSION
Issued at 200 PM EDT Mon Oct 26 2026 In terms of the sensible weather, there is quite the spread this afternoon across the Florida Keys. Portions of the Upper Keys, closest to a cyclonic disturbance centered south of the Bahamas, have remained mostly cloudy throughout much of the day, as fast- moving showers occasionally pass through. These showers have been generally shallow and light, with MRMS-derived rainfall estimates generally less than a tenth of an inch, even it some of the wetter locations. Meanwhile, in the Lower Keys, there has been very little in terms of shower activity, and the Middle Keys have served as a transitional zone for the rainfall. In the strong north to northeasterly gradient, temperatures continue to struggle to raise much above the morning lows, with most island communities hovering near 80F.

There is relatively good agreement among global ensemble numerical weather prediction guidance, supporting a relatively confidence forecast for the next several days. Very few changes were made relative to the inherited overnight forecast package.
The aforementioned disturbance will very slowly lift northward in the west-central North Atlantic through Tuesday night. The system will continue to interact with a high pressure system centered near Virginia, that will then be reinforced by a second high north of the Great Lakes region. North to northeast windy conditions will continue, with breezes slowly slackening after Tuesday night, as the disturbance moves enough northward and the pressure gradient weakens. Forecast soundings also highlight decreasing tropospheric moisture for the middle to latter part of the week, and we continue to nudge to slight rain chances beyond mid-week.
Highs should continue to hover near 80F through Tuesday, then modestly moderate for the latter part of the work week, as winds finally clock around to the northeast to east.

Outside of the windy conditions, the main weather story will continue to be coastal flooding concerns, with peak tides expected Tuesday night through Thursday night. Water levels in the Lower and Middle Keys will approach major flooding levels around the time of high tide, and the Coastal Flood Warning currently in the Upper Keys may need to be expanded. Peak water levels in the Lower and Middle Keys may approach six inches higher than experienced at around the time of high tide last evening. Although predicted tides will be on a downward trend after Thursday, it will be a slow process, with additional Coastal Flood Advisories likely needed through the weekend.

MARINE
Issued at 200 PM EDT Mon Oct 26 2026 Although we are experiencing a brief lull in wind speeds this afternoon, especially north of the Island Chain, breezes will once again freshen this evening and overnight. Frequent gusts will approach near gale levels for this period.

From synopsis, sprawling high pressure over the eastern United States will be reinforced by a secondary high north of the Great Lakes. As these features interact with a persistent low south of the Bahamas, this will sustain frequent near gale gusts this afternoon through Tuesday morning, especially across the Straits of Florida, extreme eastern Hawk Channel, and the SE Gulf waters. In addition, pulses of low level moisture will support elevated shower chances, mainly in the eastern marine zones. The secondary high will slide into the central North Atlantic for the middle to latter part of the work week, supporting slackening northeast to east breezes.

AVIATION
(00Z TAFS)
Issued at 725 PM EDT Mon Oct 26 2026 VFR conditions are forecast to prevail at both TAF sites through this period. SHRA will be in the vicinity of MTH, but is expected to remain just east of the terminal closer to a surface low over the Bahamas. Low-level winds will remain elevated due to a strong pressure gradient with N/NE sfc winds of 10-15 kts and gusts of 20-25 kts. Occasional stronger gusts may occur near passing showers.

PRELIMINARY POINT TEMPS/POPS
Key West 82 73 82 74 / 40 30 30 30 Marathon 81 73 81 74 / 40 40 40 40

KEY WATCHES/WARNINGS/ADVISORIES
FL...Coastal Flood Warning until 5 AM EDT Tuesday for FLZ076.

Coastal Flood Advisory until 5 AM EDT Tuesday for FLZ077-078.

GM...Gale Warning until 11 AM EDT Tuesday for GMZ031>035-042>044- 052>055-072>075.