textproduct: Key West

KEY MESSAGES

- Conditions will be favorable for island cloud line and associated waterspouts through the early afternoon.

- Rain chances will slowly increase into the weekend as dust concentrations decrease.

- Warm and muggy conditions will continue throughout the work week, with light and often variable breezes.

DISCUSSION

Issued at 1136 AM EDT Thu Aug 20 2026 What a difference twenty-four hours can make. The 12z morning sounding at KEY, relative to the 12z sounding Wednesday morning, sampled a nearly saturated layer from the surface up to around the 840 mb isobaric surface. The capping inversion above weakened substantially, with nearly nil inhibition and plenty of potential convective instability to be realized. Given the sampled light and generally variable winds across the Florida Keys and the adjacent marine zones, and the boundary layer moistening, we hypothesized that it would not take much to ignite an island cloud line today. Indeed, shortly after 11 AM, this indeed occurred. For the rest of the first period, expect the cloud line to wax and wane over the next several hours, with diminishing shower and thunderstorm activity thereafter. After the cloud line diminishes, plenty of time to realize advertised afternoon highs near 90F. Besides the uptick in rain chances, no changes proposed for this short term forecast update iteration.

MARINE

Issued at 1136 AM EDT Thu Aug 20 2026 Conditions will be favorable for waterspout formation through the early afternoon hours. Mariners are reminded a waterspout would most likely appear beneath a dark, flat bottom of a building cumulus line, just at the hint of rain. From synopsis, a split ridge across our waters with a nearby col will result in light and variable winds this afternoon. The split ridge pattern will remain in place through the end of the week and early in the weekend with a mostly light to gentle variable wind pattern. Winds will then increase and become more southeasterly for late weekend and into the new work week, with daily gentle to moderate breezes expected.

AVIATION

(15Z TAFS) Issued at 1136 AM EDT Thu Aug 20 2026 An island cloud line will remain in the vicinity of the terminals through at least 18z this afternoon. Have included mention of VCSH at MTH, and VCTS at EYW, to account for this, with specific impacts left to any possible needed TEMPO groups. Rain and thunder chances should gradually diminish later in the TAF period. Variable near surface winds will gradually clock around to the east to southeast overnight.

PRELIMINARY POINT TEMPS/POPS

Key West 92 82 91 83 / 20 10 0 0 Marathon 90 83 90 83 / 30 10 0 0

KEY WATCHES/WARNINGS/ADVISORIES

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