textproduct: Key West

KEY MESSAGES

- Saltwater flooding of low elevation streets and lots is likely through this 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 Lower to Middle Keys, and a Coastal Flood Warning is in effect for the Upper Keys. Coastal Flood Advisories will likely be required for the Lower to Middle Keys by tonight.

- Northeasterly swell from a Nor'easter off the East Coast will continue to produce 3 to 4 foot seas through today in the eastern Straits of Florida.

DISCUSSION

Issued at 413 AM EDT Sun Sep 27 2026

Pleasant conditions are in place across the Florida Keys this morning. Surface obs are reporting dewpoints in the upper 60s to near 70 along the lower to middle island chain and this should persist through the day today with light to gentle northerly breezes and mostly sunny skies. Water vapor satellite imagery clearly shows a strong nor'easter spinning along the New England coast, the axis of which extends south-southwest and almost directly across the Keys. This system is flanked on both sides by broad ridging, resulting in somewhat of a blocking pattern. Things will get moving again over the next couple of days as a deepening longwave trough begins to push in from the Pacific and across the Four Corners while the nor'easter breaks down and ejects towards the northern Atlantic.

Currently, tidal gauges along the eastern Florida Peninsula and now into the Keys have shown a steady rise in tidal anomalies well above projected levels. This is partly due to the Full Moon but also due to a backup of the Gulf Stream as a result of the gale force northerly winds along the East Coast associated with the nor'easter. The tide station at Ocean Reef recently reported a peak in major flood. This backup is expected to gradually work its way down the Keys over the next few days with high tide projections showing an increase, especially at high tide tonight and Monday night. As such, the Coastal Flood Advisory was upgraded to a Warning for the Upper Keys while a Coastal Flood Statement remains in effect for the Lower to Middle Keys due to saltwater flooding. An upgrade to an Advisory will likely be needed for the Lower to Middle Keys by tonight or tomorrow at the latest. Residents in the Upper Keys should take the necessary actions to protect flood-prone property. Persistent puddles around the times of high tide are almost certain to contain a mix of saltwater. Also, northerly swell in the eastern Straits of Florida will gradually subside today and tomorrow.

Longwave troughing is expected to deepen across the Southeast and into the Gulf tonight in association with the nor'easter. In the lower-levels, the Atlantic ridge will begin to build across the Keys which will promote a swing towards west-southwesterly low- level flow during the day tomorrow. We'll see a rapid resurgence in tropospheric moisture right as the mid to upper-level trough axis is deepening over the Gulf. A wet and stormy period looks to develop as early as tomorrow night with waves of activity possible through at least the middle of the week. Global models are suggesting that as the nor-easter departs into the Atlantic, leftover mid to upper-level troughing will be cutoff and left behind over the Gulf or Yucatan while the Atlantic ridge begins to establish it's dominance across the region in the lower-levels. This will be a complex setup that may culminate into a sustained wet and breezy period through the latter half of the week, becoming increasingly problematic if rounds of heavy rainfall were to compound with ongoing King Tides.

MARINE

Issued at 413 AM EDT Sun Sep 27 2026 There are currently no watches, warnings, or advisories in effect across the Florida Keys coastal waters. From synopsis, an early season cold front remains draped across the distant Straits of Florida through at least tomorrow morning, supporting light to gentle northerlies. A Nor'easter remains off the coast of New Jersey which will continue to support a northeasterly swell with large periods in the eastern marine zones through tonight, before subsiding tomorrow. The aforementioned front will begin to push back northward through the marine zones late tomorrow. Winds will then clock back to the southeast to south for early this week, also accompanied by increasing rain and thunder chances. In addition, strengthening high pressure is expected to move off the Southeast U.S. coastline around the middle to latter half of next week, merging with the Atlantic high. This will promote freshening east to southeast breezes, potentially becoming moderate to fresh.

AVIATION

(06Z TAFS) Issued at 116 AM EDT Sun Sep 27 2026

VFR conditions will continue at both TAF sites through this period thanks to a dry, post-frontal airmass. There will be enough shallow low-level moisture to support FEW/SCT cu and perhaps a few brief showers, but coverage will be minimal so precip was not included in the TAF. Sfc winds will remain generally north around 5 to 8 kts, perhaps light and VRB at times during the afternoon.

PRELIMINARY POINT TEMPS/POPS

Key West 87 77 88 77 / 10 10 30 60 Marathon 85 78 86 78 / 10 10 20 60

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Warning until 5 PM EDT this afternoon for FLZ076.

GM...None.