textproduct: Key West

KEY MESSAGES

- Saltwater flooding of low elevation streets and lots is likely through next week due to a potent King Tide. Don't drive through flooded roadways. Boaters can expect less clearance under fixed bridges.

- A Coastal Flood Statement is in effect for the Florida Keys. Coastal Flood Advisories may be required as early as Sunday night, and will likely be required for much of the Keys by Monday night.

- Increasing northeasterly swell from a Nor'easter off the East Coast will allow seas to build to 4 to 5 feet through the weekend in the eastern Straits of Florida off the Upper Keys.

AVIATION

(18Z TAFS) Issued at 140 PM EDT Fri Sep 25 2026 VFR conditions will prevail at both island terminals through 18z Saturday concern. The biggest forecast challenge will be wind direction, given the runway orientations at EYW and MTH. Winds may waffle between northwest to north and north to northeast, mainly late tonight through tomorrow morning. Have went with a prevailing north to northeast wind direction for now due to uncertainty, although this will be monitored.

PREV DISCUSSION

Issued at 455 AM EDT Fri Sep 25 2026 Mid to upper-level water vapor imagery reveals a deepening trough axis situated off the Mid-Atlantic coast while a sharp moisture gradient, extending southwest from the western Atlantic across Andros Island and through the Straits of Florida, helps to roughly delineate where the frontal boundary is currently located. Meanwhile, broad ridging to our west continues to slowly sink southward along the Texas coast. The 00Z KKEY RAOB sampled the early proliferation of dry air, especially above 500mb, but some drying is noted below 500mb as well. Currently, there are scattered showers and a thunderstorm or two being initiated by a wind surge and weak surface convergence along the front in the waters west and south of the Lower to Middle Keys. This activity is struggling to grow vertically due to the dry air aloft, and only a handful of lightning strikes have occurred. Deep west to northwesterly flow will continue to advect dry air further south towards Cuba throughout the day with the front expected to settle across the Straits. Expect freshening breezes to gentle to moderate today in the wake of the front. Hi-res guidance suggests moderate to fresh breezes may occur in the southeastern Gulf for a short period this morning, but winds are expected to slacken throughout the day. Small craft should exercise caution in the Gulf until winds decrease. Additionally, northerly swell will result in building seas of 4 to 5 feet today into the weekend in the easternmost Straits of Florida off the Upper Keys. To round things off, as we approach a peak in the astronomical tides, minor saltwater flooding is expected to occur during high tide along the Keys. This may be compounded by a backup of the Gulf stream due to the strengthening system parked off the East Coast. A Coastal Flood Statement remains in effect through this afternoon for the Florida Keys, and extensions into the coming days may be necessary.

As we head into the weekend, the early season nor'easter will continue to strengthen and loiter along the New England coast. Embedded shortwaves rotating south through the mean troughing will provide reinforcing surges of dry air into Florida and across the Keys on Saturday. This will also help to provide at least some measure of mid to upper level cyclonic flow across the area, but showers/storms will be limited in coverage and vertical growth by the preceding dry airmass in place. As such, the forecast generally calls for below-normal rain chances for the next few days. Slight chances will be focused in the Straits of Florida near the stalled front, or in the Florida Bay and Upper Keys associated with any southward moving activity from the Florida mainland. Guidance continues to trend towards lower dewpoints in the upper 60s to lower 70s Saturday afternoon into Sunday along the Island Chain with temperatures running perhaps a couple of degrees lower than usual. Not a wild temperature swing, but certainly noticeable from a lower humidity perspective.

By early next week we will begin to gradually transition back into more of a wet pattern as low-level Atlantic ridging begins to expand across the area, allowing low-level winds to swing back to south- southwesterly. This will help to force tropical moisture northward across the Keys as the remnant front completely washes out. However, in the mid to upper-levels troughing associated with the East Coast low will begin to once again amplify across the Southeast and into the Gulf, placing the Florida Keys and surrounding waters back into a favored zone for lift. This is likely to become maximized by the middle of next week in which above-normal PoPs are expected to develop.

MARINE

Issued at 1115 AM EDT Fri Sep 25 2026 Any remaining scattered showers and thunderstorms will gradually wane across the Straits of Florida over the next several hours. Tides will continue to build over the weekend, peaking Sunday through Tuesday. Boaters can expect less clearance under fixed bridges, especially around the time of high tide.

From synopsis, an early season cold front will continue to push southward through the Straits of Florida this afternoon. Gentle to moderate north to northeast breezes will gradually slacken in the wake of the front, becoming light to gentle over the weekend. A Nor'easter off the Eastern Seaboard will support a northeasterly swell in the eastern marine zones through Sunday. The front will push back northward late Sunday night through the marine zones. Winds will then clock back around to the southeast for early next week, also accompanied by increasing rain and thunder chances.

PRELIMINARY POINT TEMPS/POPS

Key West 88 77 87 77 / 10 10 10 10 Marathon 86 77 86 77 / 10 20 10 10

KEY WATCHES/WARNINGS/ADVISORIES

FL...None. GM...None.