textproduct: Key West

KEY MESSAGES

- Island cloud line formation will be possible in the late morning or afternoon hours through the weekend.

- Waterspouts will be possible with any developing island cloud line.

- Conditions will remain seasonably warm and muggy, with heat indices approaching near 100F each afternoon through early next week.

DISCUSSION

Issued at 421 AM EDT Fri Jun 12 2026 Anyone in the Florida Keys may wake up to a nearly shower free environment as seen by both the KBYX and KAMX radars. GOES East observations show skies are not entirely cloud free across the Florida Keys. Nighttime microphysics scans show high altitude cirrus debris cloud associated with a tropical wave over the Yucatan peninsula are streaming over the Lower Keys and our western waters. Meanwhile, wind observations at both EYW and MTH are both below 10 knots. Temperature measurements at Big Pine Key, down to 77F, and the Key West WFO, down to 80 F, indicate the winds are light enough and skies clear enough to see radiative cooling on the larger islands. This does not mean we will see a break from the humidity. Dew points along the island chain are still in the mid 70s. Overall, the weather pattern developing over the Florida Keys looks muggy with light winds today.

What large scale features are playing a role in the current weather pattern? The aforementioned tropical wave was absorbed into a Central American Gyre over southern Mexico and Central America. Its role for Florida Keys weather is that it will weaken nearby high pressure systems, leading to our light breezes, and send waves of high altitude ice clouds across the eastern Gulf. Meanwhile, the Atlantic High has moved far to the East of Bermuda. A stronger high pressure system over the eastern United States could build winds across the Keys, but a series of lows unleashed multiple rounds of severe convection across the Midwest which also weakened the southeastern US high. The result is a relatively stagnant pattern across the Florida Keys. Breezes are light to gentle, divergence in the upper atmosphere is elsewhere, suggesting the weather for the upcoming weekend will be defined by diurnal heating cycles. There is one more caveat, a dry layer identified by last night's 00Z sounding between 800 and 650 mb. NASA forecast models that focus on aerosols highlighted a region of higher than normal optical thickness over South Florida and the Keys. It's possible that one of the reasons shower coverage has been so sparse the past few days was a lingering layer of Saharan dust.

What does this mean for the upcoming weekend and next week? Models suggest a drier pattern is setting up across the Keys. The Central American Gyre will divert the most moisture-laden air west of the Keys. Model ensembles show a pronounced trough forming over the eastern United States, which would prevent the southeast US high from redeveloping and freshening breezes across the Keys. In this environment, the main concerns become cloud line showers, potential waterspouts, and heat risk. Heat indices near 100 F are possible, and we are not even in the hottest month of the year. Stay hydrated, watch clouds over the water, and stay cool when possible!

MARINE

Issued at 421 AM EDT Fri Jun 12 2026 No watches, warnings, or advisories are in effect for the Florida Keys coastal waters. From synopsis, High pressure across the southeastern United States weakened over the past couple of days while the Atlantic High moved further east. Breezes slackened to light to gentle east southeasterlies as a result, and are on track to become light later this weekend. Shower coverage will remain low while a layer of dry air lingers in the lower atmosphere.

AVIATION

(06Z TAFS) Issued at 421 AM EDT Fri Jun 12 2026 VFR conditions will prevail at EYW and MTH for the upcoming TAF period. Near surface winds will remain east to southeasterly and below 10 knots. An occasional shower may be able to develop and cause MVFR to IFR CIGs, but confidence in timing and location is too low to include in the TAFs.

PRELIMINARY POINT TEMPS/POPS

Key West 89 81 89 81 / 20 10 20 10 Marathon 89 81 90 81 / 20 10 20 10

KEY WATCHES/WARNINGS/ADVISORIES

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