textproduct: Key West

KEY MESSAGES

-Moisture will begin to return Saturday; elevated rain and thunderstorm chances will prevail Saturday evening through Sunday morning.

-Gentle to moderate breezes will prevail into tonight as high pressure slides over the Big Bend into the western North Atlantic.

-Small Craft Advisory headlines are becoming increasingly likely for Monday and Monday night after a strong front pushing through the Keys results in freshening breezes.

DISCUSSION

Issued at 1014 PM EST Fri Dec 12 2025 Sky watchers across the Florida Keys would notice a rather sudden increase in cloud cover across the CWA. High altitude cirrus clouds generated by convection along a weak surface trough south of Cuba began propagating north towards the Florida Keys this evening. GOES East nighttime microphysics scans indicate the cirrus is still rather thin, so any stargazers may get a few breaks during the overnight hours. Meanwhile, the mixture of additional cloud cover and gentle to moderate breezes in the northern waters indicates temperatures are unlikely to drop to last night's lows in the lower 60s. Meanwhile, breezes managed to surge along the reef to moderate to fresh. In hindsight, 20 knot gusts should not be too surprising. Low altitude winds measured by the KKEY 00Z sounding sampled 20 knot winds at 1000 feet. Above the boundary layer, the atmosphere was still defined by sinking air aloft. Layers of the aforementioned cirrus were the only source of moisture above the lowest few thousand feet, and the sampled PWAT was below the 25th percentile for the day. However, that layer of cirrus is a harbinger for tomorrow's weather pattern.

The trough south of Cuba happens to be the lingering remnant of a front that pushed through the Keys earlier this week. Environmental patterns are shifting enough that this feature will lift back north towards the Keys tomorrow as a broad warm front. Hi res guidance eventually coalesced lines of showers moving north across the Straits towards the island chain. In addition, a weak upper altitude jet is progged to be in a favorable position to support thunderstorm development. Given this information, thunderstorm PoPs were increased tomorrow and tomorrow night across the Straits, the Island Chain, and some areas of the northern waters. Wind speeds were also increased for overnight through tomorrow evening. Currently, convective allowing models suggest tomorrow evening will have the highest likelihood of thunderstorms for the period.

MARINE

Issued at 1013 PM EST Fri Dec 12 2025 No watches, warnings, or advisories are in effect for the Florida Keys coastal waters. From synopsis, high pressure drifting eastward into the western North Atlantic will result in gentle to moderate, occasionally fresh, northeast to east breezes overnight. The next frontal boundary is progged to push through the Florida Keys marine zones on Sunday night. Ahead of the front, elevated chances for showers and thunderstorms will be possible late Saturday through early Sunday. In the wake of the frontal passage, fresh to strong northeasterly breezes are expected Sunday night through at least Tuesday.

AVIATION

(00Z TAFS) Issued at 1013 PM EST Fri Dec 12 2025 VFR conditions will prevail for the 00Z TAF period at EYW and MTH. Near surface east northeasterly winds will slowly veer easterly and begin increasing towards near 10 knots. Cloud and shower coverage will slowly increase after sunrise, and shower coverage will be sufficient for VCSH after 18 UTC. Shower coverage will be greatest over the Straits, and thunderstorms are possible in the last 6 hours of the TAF.

CLIMATE

On this day in 1957, the daily record low temperature of 42F was recorded at Marathon. Temperature records for Marathon date back to 1950.

PRELIMINARY POINT TEMPS/POPS

Key West 71 81 70 79 / 10 30 70 40 Marathon 72 79 71 78 / 10 30 70 50

KEY WATCHES/WARNINGS/ADVISORIES

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