textproduct: Key West

KEY MESSAGES

- A Coastal Flood Statement remains in effect, and particularly low lying areas will see some saltwater ponding around the times of high tide.

- A dry air mass will linger over the Florida Keys during the rest of the holiday weekend. Shower coverage tonight is on track to decrease until Monday night.

- A weak frontal passage is expected across the Keys sometime Monday night/Tuesday. This will lead to slightly cooler temperatures, a drop in dew points, and increased shower chances.

UPDATE

Issued at 908 PM EDT Sun Oct 11 2026 A rather pronounced moisture gradient remains in place this evening across the Florida Keys with blended TPW imagery showing a pocket of dry air across most of the island chain and The Bahamas as mid/upper level ridging extends westward from the Subtropical Atlantic. In fact, the 12/00Z KEY RAOB has a rather dry appearance, particularly in the mid levels where mid RH values are just 38%. Additionally, PWATs were sampled at 1.66 inches, which is right around the daily mean for this time of the year per SPC sounding climatology. Meanwhile, there is a narrow plume of tropical moisture directed from the SE Gulf waters and into the central FL peninsula, which is pooling along a frontal boundary dropping slowly southward. For tonight, the drier air mass will continue to hold its grip across the Florida Keys and yield just slight PoPs with another round of muggy conditions as overnight lows continue to be in the lower 80s and dewpoints in the upper 70s. However, there will be a subtle decrease in heights aloft overnight into Monday as an upper level trough swings off the eastern Seaboard and pushes the aforementioned ridge further out into the Atlantic. This will ultimately send the frontal boundary into south FL on Monday with this feature then approaching the Upper Keys by Monday night. Thus, most of the day tomorrow should also be fairly dry before a slight increase by Monday night as an increasingly narrow corridor of enhanced moisture spreads into the area with the approach of the frontal boundary. Overall, the ongoing forecast continues to be in good shape with no changes planned at this time.

DISCUSSION

Issued at 320 PM EDT Sun Oct 11 2026 The flow field across the Florida Keys finally began to change this morning. GOES East water vapor satellite observations indicate there is a pronounced moisture gradient currently over the Florida Keys. Dry air associated with a rebuilding subtropical ridge slowly moved over the nearshore and offshore waters this morning, as evidenced by estimates of environmental PWAT from GOES-East. There is a gradient of approximately 1.5 inches to around 2.2 inches from the Upper Keys to the Lower Keys. The problem was that mixture between heavily saturated and drier air across the Keys was enhancing instability over the Outer Gulf waters. The extensive amount of moisture observed by this morning's 12Z KKEY sounding, nearly 2.5 inches of precipitable water, existed in an atmosphere with little to no inhibition. The source of lift provided by weakly confluent flow in the lower levels allowed thunderstorms to develop just northwest of Key West. However, as the drier air stabilizes over the Florida Keys, one can expect shower coverage to decrease. The other issue for showers this afternoon and tonight is that this dry layer is stuck above the surface layer. Even though skies are on track to clear, dew points are forecast to remain in the upper 70s to near 80 across the island chain. Tonight is setting up to be another muggy, humid night for the Keys.

There are a couple of points of uncertainty this week. First, a frontal boundary extending from a large mid-latitude cyclone, the remains of Major Hurricane Isaias, is primed to stall near the Florida Keys during the early part of the week. Statistical guidance suggests the front will be able to move south of the island chain, but exactly how much temperatures and dew points will drop remains uncertain. While a few days ago, statistical models suggested dew points could decrease to the upper 60s, the near 70 to the lower 70s appears more likely for the island chain. Breezes are expected to freshen to gentle to moderate after frontal passage. Shower coverage is expected to pick back up sometime midweek.

The most notable feature for the forecast is what models are resolving over the weekend. Deterministic models suggest a potent front could move across the Keys on Saturday to Sunday. However, the seven day forecast is a bit far out. Expect this forecast to change quite a bit as we get closer to the weekend.

MARINE

Issued at 320 PM EDT Sun Oct 11 2026 There are no watches, warnings, or advisories currently in effect for the nearshore or offshore waters of the Florida Keys. Boaters should be aware of less clearance under fixed bridges around times of high tide as a Coastal Flood Statement is in effect for the Florida Keys. Breezes slackened to gentle to moderate southeasterlies across the reef as a drier air mass moved over the eastern waters.

From synopsis: A couple of nearby features will define the weather across the Florida Keys for the first half of the week. The Atlantic Ridge is gradually weakening and moving east towards the central Atlantic. Another weak high pressure system is located over the Gulf. Between the two pressure systems lies a weak frontal boundary that is set up across central Florida. The front is primed to pass across the Keys waters sometime early in the week, and promote gentle to moderate northeast to east breezes. Shower chances are forecast to be slight before mid-week before the previously mentioned front stalls near the Keys waters. Late in the week, there is a chance a strong cold front could develop and move towards the Florida Keys. Frontal passage with this cold front could occur over next weekend, and we will continue monitoring this system.

AVIATION

(00Z TAFS) Issued at 908 PM EDT Sun Oct 11 2026 VFR conditions will prevail throughout the forecast period with NE winds at 5-10 kts. While isolated SHRA may occur at times, any activity that develops is expected to be light enough with little to no restrictions.

KEY WATCHES/WARNINGS/ADVISORIES

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