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 Lower to Middle Keys, and a Coastal Flood Advisory is in effect for the Upper Keys. Coastal Flood Advisories will likely be required for all of the Keys by Monday night.

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

AVIATION

(18Z TAFS) Issued at 138 PM EDT Sat Sep 26 2026 VFR conditions will prevail at EYW and MTH for the upcoming TAF period. Dry air aloft will keep cloud cover sparse, though occasional MVFR CIGs are possible. SHRA are percolating west of the terminals, but VCSH conditions are unlikely. Near surface winds are on track to shift north northwesterly after sunset.

PREV DISCUSSION

Issued at 502 AM EDT Sat Sep 26 2026 A significantly drier airmass aloft continues to expand across the Florida Keys early this AM. Based on water vapor imagery, the cold front has progressed slightly farther south than expected, extending south-southwest from the parent nor'easter spinning off the Mid- Atlantic/New England coast, through the Bahamas and across to even slightly south of Cuba. Gentle to moderate northerly breezes will continue across the Keys and surrounding waters this morning, but will become light to gentle by this afternoon. The nor'easter will remain trapped between broad Atlantic ridging and persistent ridging over the Central CONUS before eventually breaking down and ejecting towards the northern Atlantic during the Monday to Wednesday timeframe. In the meantime, deep west-northwesterly flow will continue across the Keys this weekend as embedded shortwaves rotate around the coastal low and maintain some measure of cyclonic flow over the eastern Gulf. We're already seeing the effects of this with isolated showers ongoing near the Lower Keys and in the Straits of Florida despite a deep layer of dry air measured on our 00Z RAOB above 900mb. MIMIC-TPW imagery shows even drier air surging south in the eastern Gulf. Any isolated development will remain rather benign today and tomorrow, and most of the day will feature mostly sunny skies with highs in the mid to upper 80s. Some locations along the Island Chain will see dewpoints in the upper 60s to near 70 degrees on Sunday which will drop humidity values down into the 50-60% range.

Our primary concern over the next couple of days and potentially into next week will be saltwater flooding of low-lying areas along the Keys caused by a peak in astronomical tides compounded by a backed up Gulf Stream due to the strong nor'easter and associated gale force winds along the East Coast. A Coastal Flood Advisory has been issued for the Upper Keys while a Coastal Flood Statement remains in effect for the Lower to Middle Keys through at least this afternoon, but extensions are likely. Eventual upgrades may be needed for the Lower/Middle Keys early next week.

Speaking of next week, it certainly looks as though our below-normal rain chances will be short-lived. On Monday, the lower-levels of the atmosphere will become influenced by Atlantic ridging which will extend across the Keys and promote a switch back to low-level southerly flow. Meanwhile to our north, the continental ridge is progged to retrograde westward just enough to allow the upper-level trough along the coast to deepen across the Southeast and into the Gulf. By Monday night, we'll see a quick resurgence in moisture content with increasing rain and thunder chances. The mid to upper- level trough will continue to provide forcing across the area through at least Wednesday, even as the nor'easter begins to lift away, leaving behind residual upper-level troughing across the Florida Peninsula to as far south as the Yucatan. Global models indicate that piece of left behind upper-level energy may begin to deepen near the Yucatan by the middle to end of the week, potentially sustaining an active period across the Florida Keys through the end of the forecast period. Unfortunately, a wet forecast on top of King Tides may exacerbate the flooding issues, but the details will be ironed out as we get closer.

MARINE

Issued at 1032 AM EDT Sat Sep 26 2026 Shallow isolated showers will wax and wane over the waters of the Florida Keys. Marine observations are measuring gentle to moderate north to northeasterly breezes.

From synopsis: An early season cold front will remain draped across the distant Straits of Florida for much of the weekend, supporting light to gentle northerlies. A Nor'easter off the Eastern Seaboard will support a northeasterly swell with large periods in the eastern marine zones through Sunday. The front will push back northward on Monday through the marine zones. Winds will then clock back around to the southeast to south for early next week, also accompanied by increasing rain and thunder chances.

PRELIMINARY POINT TEMPS/POPS

Key West 78 87 78 88 / 10 10 10 30 Marathon 77 85 78 87 / 10 10 10 30

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 6 AM EDT Sunday for FLZ076.

GM...None.