textproduct: Key West

KEY MESSAGES

- A moisture surge will support bouts of elevated rain and thunder chances for the remainder of the Labor Day holiday weekend.

- The primary threat for any stronger thunderstorms will be dangerous lightning strikes. When thunder roars, go indoors. If on a boat, stay low, or go below.

- Heat indices will approach the mid 100s daily, with little relief in the muggy conditions overnight. Know the signs of heat stress, take frequent breaks, and stay hydrated.

DISCUSSION

Issued at 1100 AM EDT Sun Sep 6 2026 The 12z sounding at KEY sampled a modestly inhibited low-level environment, but with ample moisture to work with. Surface analysis places a weak stationary front draped across the Southeast, with a split ridge pattern across the Florida Keys. Sometimes it is humbling to remember that it doesn't take much for convective initiation across the Keys in early September. KBYX radar has been active all morning, with the focus of convection across much of southeastern Gulf northwest of the Lower Keys.

A very challenging forecast for today, with mesoscale processes (including island cloud lines and boundary collisions) dictating the sensible forecast. With Mainland heating, we expect winds to go light and variable through the afternoon, allowing cumulus congestus to congeal into an island cloud line across at least the Lower Keys. Interacting with boundaries originating from existing convection across the Gulf waters, a solid chance level rain and thunder forecast seems prudent. No changes planned for this late morning forecast iteration.

MARINE

Issued at 1100 AM EDT Sun Sep 6 2026 o watches, warnings, or advisories are currently in effect for the Florida Keys waters. From synopsis, light to gentle southeast breezes will prevail through mid week, as weak steering flow persists across the region. Thereafter, breezes will freshen to gentle to moderate, as high pressure builds in. Waves of low-level moisture pushing across the Keys will support elevated rain and thunder chances through this afternoon, possibly returning to near normal by mid week.

AVIATION

(12Z TAFS) Issued at 1100 AM EDT Sun Sep 6 2026 VFR conditions are expected to prevail at both EYW and MTH through 12z Monday morning. With that said, convective activity is expected to grow through the early afternoon hours, with impacts to the terminals possible. Will monitor this, but given the lack of certainty in terms of timing, will leave a general mention of VCSH for now.

KEY WATCHES/WARNINGS/ADVISORIES

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