textproduct: Key West

KEY MESSAGES

- Major coastal flooding in the Upper Keys and moderate to minor coastal flooding in the Middle and Upper Keys is ongoing, especially during times of high tide.

- A prolonged period of Small Craft Advisory conditions are expected from tonight through early next week. Near-gale breezes will be possible at times Sunday evening through Monday evening. - Little to any relief in significant coastal and marine impacts are expected into at least the middle of next week. Residents and visitors should take the necessary actions to protect flood- prone property.

DISCUSSION

Issued at 312 PM EDT Fri Oct 23 2026

The synoptic pattern remains highly amplified across the CONUS with longwave troughing across the eastern and western US, separated by a ridge across the Plains, which extends into the Canadian Prairies. The trough across the eastern US and western Atlantic has a positive tilt to it with its base reaching as far south as the northern Caribbean. This trough has brought some exceptionally cold air aloft to the Florida Keys with 500 mb temperatures sampled on the 23/12Z KEY RAOB of -13.9C, essentially shattering the daily minimum for this date. This has directly contributed to rather extreme mid-level lapse rates with values around -8.2C, though a stable layer around 850-750 mb will make it difficult for parcels to overcome, especially considering the limited instability in place. However, there will continue to be the potential for a few cores to overachieve through tonight if some updrafts are able to overcome the inhibition, especially over the Gulf stream waters of the Straits. Regardless, precipitation trends will need to be monitored closely area-wide closely through the remainder of the day as additional activity could also drift across the Gulf and Bay side waters this evening as highlighted in some recent CAMs.

A potent northern stream shortwave will shift out into the north Atlantic off of the Canadian Maritimes while the trough axis further south slowly shifts eastward across the Florida Peninsula and Cuba. There is some indication that the base of this trough closes off over the weekend but there is uncertainty on whether or not this feature will just remain an open trough. Regardless, this feature will support substantial PVA and divergence aloft across the SW Atlantic. This will yield in the development of an elongated surface trough/low with this feature emerging out of the Caribbean before gradually drifting to the NNE as it gains latitude. Meanwhile, an expansive area of high pressure across New England will interact with this feature to make for an extended fetch of northeasterlies across the Atlantic. This will create a variety of hazards across the KEY CWA with major coastal flooding across the Upper Keys and at least moderate flooding across the Middle and Lower Keys, especially during periods of high tides. As a result, a Coastal Flood Warning is in effect in the Upper Keys and Coastal Flood Advisories are in effect in the Middle and Lower Keys. Needless to say, marine conditions will also be hazardous for an extended period at least Small Craft Advisory conditions expected into at least early next week and a period of gales even can't be ruled out particularly Sunday into Monday. With the best forcing for ascent expected to be east of the area, QPF amounts should generally be manageable over land areas throughout the weekend, which should help somewhat from a drainage perspective but if any heavier downpours do occur during times of high tides, it will worsen the flooding impacts from the already overwhelmed drainage systems from backwater effects.

By early next week, there is greater than normal uncertainty on exactly when this amplified and stagnant weather pattern finally breaks down. The GFS shows one or multiple elongated surface lows lingering in the western Atlantic basin and the ECMWF keeps a weaker surface reflection retrograding westward from the Bahamas with this feature eventually weakening as upper trough finally opens. Even with these differing solutions, the main message is clear: there will continue to be significant coastal flooding impacts that will continue across the entirety of the island chain as persistent northeasterlies and the arrival of the full moon coincide. Thus, little to no relief is anticipated through early to mid week regarding coastal flooding concerns and marine impacts. However, global models finally hint at a possible end to this pattern by the end of next work week as a ridge builds in leads to a slackening pressure gradient, which will hopefully signify the start of a gradual improvement in coastal flooding and marine impacts.

MARINE

Issued at 312 PM EDT Fri Oct 23 2026

A prolonged period of Small Craft Advisory conditions will commence tonight and linger through at least early next week as a strong pressure gradient is leading to breezy northeasterly across the Florida Keys coastal waters. In addition, a period of gale conditions can't be completely ruled out Sunday into Monday and eventual gale headlines could be needed over the weekend. While there may be brief lulls in winds slightly decreasing to small craft exercise cautionary level during the afternoon hours, any improvements will be very brief. Regardless, marine conditions will be hazardous for a prolonged period area-wide with meaningful improvements possibly not arriving until late next week. In addition, isolated to scattered showers and thunderstorms could also occur each day, especially over the Straits as an upper level disturbance lingers over the region.

AVIATION

(18Z TAFS) Issued at 312 PM EDT Fri Oct 23 2026

Breezy NE winds will be in place throughout the TAF period with occasional gusts of 20 kts or more possible at times. While some SHRA activity can't be ruled out, confidence is low on whether or not this activity will directly impact either of the island chain terminals. Thus, this has not been mentioned in the most recent TAF issuance. Otherwise, VFR conditions will generally prevail throughout the period.

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Warning until 5 AM EDT Saturday for FLZ076.

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

GM...Small Craft Advisory from 8 PM this evening to 8 PM EDT Monday for GMZ031>035-042>044-052>055-072>075.