textproduct: Key West

KEY MESSAGES

- Moderate to major saltwater flooding of low elevation streets and lots is likely to continue over the next few day or so due to King Tide. Don't drive through flooded roadways. Boaters can expect less clearance under fixed bridges.

- A Coastal Flood Warning is in effect for the Upper Keys, particularly along the sounds, bay side of Key Largo. A Coastal Flood Advisory is in effect for the Middle and Lower Keys.

- A wet pattern is expected for the next several days across the Keys. This will maintain above normal rain and thunder chances through at least Thursday.

DISCUSSION

Issued at 436 AM EDT Tue Sep 29 2026

An incredibly messy but dynamic weather pattern is setting up across the Florida Keys this morning. Let's break it down. At the surface we have weak ridging occurring which is leading to chaotic, but light surface winds. In the lower levels the ridge axis of an Atlantic Ridge lies just to our south but is steadily marching northward. In the mid and upper levels we have a pronunced, deep trough that extends from near the Great Lakes Region well south across the Gulf Basin and into the western Caribbean. This feature is providing broad cyclonic flow aloft as well as the occasional shortwave that has ejected northeastward.

The aforementioned Atlantic Ridge axis will continue lifting northward today. As it does, it will help to align our surface winds more out of the east to southeast. In addition, the steering flow more become more southerly, allowing for better moisture transport from the western Caribbean ahead of the mid/upper level trough. Thus far the trough has resided to our west with a plethora of convection erupting throughout the last day or so. However, as this activity tries to move northeast and away from the trough, it has encountered more stable and relatively drier air. This has kept much of the precipitation from reaching the Florida Keys.

Today should be the transition point for the Keys. The mid/upper level trough will slowly edge eastward today allowing for a better alignment of moisture and lift. The fly in the ointment is the low level ridge axis lifting northward. This will cause a southerly wind below 700 mb and could bring in low level dry, warm air advection. This may counter the increasing moisture aloft, leading to an overall lower coverage of showers and thunderstorms for today. Hi-res CAMs continue to advertise that we will have enough synoptic forcing to overcome the more mesoscale effects. Time will tell if this actually happens.

Once this feature sets in, we can expect multiple days of wet, active weather through at least Thursday. Thereafter, a ridge out across the Atlantic will shift further to the west and retrograde the mid/upper level trough into the Bay of Campeche. This would lower our rain chances back closer to normal with a moist east to southeast flow.

MARINE

Issued at 436 AM EDT Tue Sep 29 2026

A much wetter than normal pattern is in place across Keys waters, lasting through the night and for at least the next several days. As result, periods of poor visibility, locally strong and gusty winds, and thunderstorms can be expected. Aside from convective influences, surface winds will be gentle out of the southwest, becoming southeast to south overnight due to the western flank of a sloppy pressure ridge remaining across our area.

AVIATION

(06Z TAFS) Issued at 436 AM EDT Tue Sep 29 2026

A wetter than normal pattern is in place across the Keys, which will result in periods of sub VFR conditions today. There is also a good chance that these periods will be accompanied by thunderstorms. Outside of convective influences, surface winds are expected to start out light and variable and become east to southeast by the afternoon.

PRELIMINARY POINT TEMPS/POPS

Key West 88 77 88 78 / 70 70 80 70 Marathon 86 78 87 79 / 70 60 70 70

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Warning for FLZ076.

Coastal Flood Advisory for FLZ077- 078.

GM...None.