textproduct: Key West

KEY MESSAGES

- There is a marginal risk for excessive rainfall through Thursday morning as tropical moisture propagates across the area over the next couple of days. - Drier air associated with a cold front will arrive late this week and into the weekend, limiting the risk of excessive rainfall, though some rain chances will linger.

- Increasing northeasterly swell in the wake of the cold front will allow seas to build up to 5 feet by the end of the week and into the weekend, especially in the easternmost Straits of Florida.

DISCUSSION

Issued at 1015 AM EDT Wed Sep 23 2026 The wet season continues this morning across the Keys. Analysis of GOES East water vapor imagery indicates an upper level trough is located over the northeastern Gulf which is funneling moisture across South Florida and the Keys. Showers have been more prominent over the Upper Keys this morning thanks to a low level reflection of the aforementioned trough. This morning's 12Z KKEY sounding sampled an environmental PWAT one hundredth of an inch away from tying the record high of 2.47" for the day. Overall, the environment is extremely moist and showers that do manage to form will be capable of generating heavy, localized rainfall. Shower movement is also very slow, so a shower that forms over an island is likely to remain there until it collapses.

What happens during the rest of the day? Showers are on track to wax and wane throughout the afternoon. Near surface winds will remain chaotic near showers. Heavier rainfall is also, unfortunately, timed with a high in the tidal cycle. A coastal flood statement is thus in effect. Temperature- wise, the widespread cloud cover will keep highs on the cooler side. No changes are necessary for the morning update. Just monitor the radar because when thunderstorms begin to redevelop, this is an environment where a small cumulus cloud can grow to a 50,000 foot cumulonimbus in 20 to 30 minutes.

MARINE

Issued at 1015 AM EDT Wed Sep 23 2026 From synopsis: Unsettled weather will persist through the next few days as deep tropical moisture lingers across the region, which will support scattered to numerous showers and thunderstorms at times. Breezes outside of convection will generally remain light to gentle out of the south the next several days with brief periods of moderate breezes, mainly in the overnight and early morning hours. Winds briefly become light and variable on Thursday before taking on a northerly heading in the wake of a frontal boundary that is forecast to push southward across the Keys waters late in the week. In addition, seas will also start to build by the end of the week and into the weekend as northerly swells build following the frontal passage, especially in the eastern Straits of Florida.

AVIATION

(12Z TAFS) Issued at 1015 AM EDT Wed Sep 23 2026 VFR conditions will prevail at EYW and MTH for the TAF period. An environment primed for SHRA will keep VCSH in the forecast, but a lull in the early afternoon is expected. TS chances are on track to increase in the late afternoon as near surface winds shift westerly.

PREV DISCUSSION

Issued at 454 AM EDT Wed Sep 23 2026 The radar remains active across the Florida Keys and surrounding waters early this morning. A persistent zone of cyclonic flow remains in place over the region associated with low to mid-level troughing which is extended from the western Atlantic into the eastern Gulf towards the Yucatan Peninsula. In the upper-levels, a longwave trough is extending south from a low over the Great Lakes region all the way to the Yucatan, placing the Keys within a favorable zone for lift. The combination of these features in addition to a high influx of tropical moisture over the area will continue to promote scattered to numerous showers and occasional thunderstorms across the Florida Keys today. Showers/storms will be highly efficient rain producers, easily capable of 2-3" per hour rain rates. In addition, as we approach the upcoming full moon, high tides will peak above normal and the Coastal Flood Statement remains in effect through this afternoon. The main concern is that these two issues could compound to result in rapid instances of localized flooding along the Keys, particularly in poor drainage areas during high tide.

Meanwhile, a stalled surface front along the Gulf coast will be forced to the south Wednesday night and Thursday as the mid to upper-level trough shifts eastward towards the Mid-Atlantic region while stubborn deep-layer ridging remains parked over the ArkLaTex. This orientation is expected to culminate into the arrival of the first cold front of the season by the end of the week. This should initially maintain above normal rain chances until dry mid-level air advects south across the area by early this weekend, dropping rain chances to a seasonable level on Saturday. At this time, it's uncertain how far south the front will progress before eventually stalling, but current projections place the east to west oriented boundary across the Florida Straits by Sunday with deep west to northwesterly flow developing over the area. If the front were to stall further north than expected, it's likely that PoPs would remain elevated. Regardless, we're not expecting much of a noticeable temperature change with the frontal passage, but if we're lucky, afternoon dewpoints could briefly dip into the lower 70s, perhaps upper 60s in spots, along the Island Chain on Saturday. This will be short-lived however, as the front lifts back to the north early next week allowing for a resurgence in high moisture content across the area as a subsequent mid to upper level trough axis amplifies over the Deep South into the Gulf.

PRELIMINARY POINT TEMPS/POPS

Key West 89 79 90 79 / 70 40 40 50 Marathon 87 80 88 79 / 70 50 50 50

KEY WATCHES/WARNINGS/ADVISORIES

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