textproduct: Key West

KEY MESSAGES

- Measurable rain chances will remain low through the weekend, only up to 10% for each forecast period.

- Conditions will remain seasonably warm and muggy, but we may see heat index values above 105F, particularly along the Upper Keys, through Friday.

DISCUSSION

Issued at 1029 PM EDT Wed Jun 17 2026 GOES-19 composite synoptic analysis highlights anticyclonic surface flow extending across the North Atlantic westward to the Florida Peninsula. A high pressure system anchored southeast of Bermuda is responsible for this flow, supporting light to gentle southeast to south breezes across the Keys at this late evening hour. To the west, Tropical Storm Arthur in the Gulf continues to crawl slowly northeastward towards the Louisiana coastline, with associated anticylonic flow aloft advecting scattered cirrus towards the Keys marine zones. KBYX radar is void of any meteorological echo returns in our CWA, although there are occasional clusters of remnant showers and thunderstorms north of Cuba. Temperatures are generally in the mid 80s across the Island Chain.

For tonight, the 12z sounding at KEY did sample a somewhat moistened layer up to around 850 mb, as the modified Saharan Air Layer (SAL) observed in the sounding 24 hours ago seems much less discernible. Tonight's sounding also sampled somewhat veered low level breezes, with limited surface-based inhibition. All available numerical weather prediction guidance also highlights a modest wind surge in the overnight hours, supporting meager confluence. Given these factors, an isolated shower or thunderstorm cannot be ruled out overnight, particularly in the favored late overnight period towards sunrise. No changes proposed to the inherited afternoon forecast package.

MARINE

Issued at 1029 PM EDT Wed Jun 17 2026 There are no watches, warnings, of advisories in effect for the Florida Keys local waters. From synopsis, a weak high pressure system in the central North Atlantic will support light to gentle breezes persisting this evening across the Florida Keys coastal waters. The high will begin to strengthen overnight, supporting slightly freshened breezes through the end of the work week. As a weak frontal boundary approaches the Florida Peninsula, the high will once again weaken, supporting a return to light to gentle breezes, becoming light and variable at times, through Monday.

AVIATION

(00Z TAFS) Issued at 1029 PM EDT Wed Jun 17 2026 Although a passing shower or thunderstorm cannot be ruled out throughout the TAF period in the vicinity of the terminals, any impacts to visibilities or ceilings would be very brief and minimal. Near-surface winds out of the southeast south may becoming variable at times after 18z Thursday afternoon.

KEY WATCHES/WARNINGS/ADVISORIES

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