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.

- Westerly swell generated by Post-Tropical Cyclone Isaias will gradually subside across the western half of the coastal waters this evening.

- Elevated rain chances are expected tonight. Shower chances will decrease during the remainder of the holiday weekend.

DISCUSSION

Issued at 225 PM EDT Sat Oct 10 2026 Weather across the Florida Keys turned out to be surprisingly uneventful this Saturday. Shower development was limited to the Outer Gulf waters and the western waters of the Florida Straits. Meanwhile, the morning sounding sampled a daily record PWAT value above 2.3 inches. Satellite observations from CIMSS-MIMIC estimated moisture totals closer to 2.1 to 2.2 inches this morning. However, if one looks outdoors the atmosphere does not appear very saturated. Clouds are struggling to form across the eastern waters surrounding the Keys, and the KBYX radar detected sparse shower activity, if any, east of the Lower Keys earlier today. Dew points in the upper 70s indicate more than enough moisture is present for widespread showers. Why has shower coverage been so sparse?

Low level winds are likely the reason we have seen a lack of shower activity. Moderate to fresh southerly breezes were present across the western Straits this morning while gentle to moderate southeasterly to south breezes were observed along the reef. This resulted in a region of low level divergence across the Keys, except for where winds were accelerating over the Outer Gulf. However, as what used to be Hurricane Isaias moves further north into the southeastern United States, breezes are on track to slacken and back southeasterly. Even though more than enough moisture is present, it is likely showers will struggle to form until winds shift further to the southeast. The most recent statistical guidance suggests the wind shift will occur after sunset. Tonight, we are forecasting that shower coverage will increase while winds slacken and back to gentle to moderate southeasterly breezes.

Looking ahead, there are a few features of interest. A tropical upper tropospheric trough is still spinning south of Cuba. Post- tropical cyclone Isaias is being absorbed into the mid-latitude flow field over the southeastern US. There are also two regions of high pressure; one is located over southeastern Texas, while the other is beginning to move into the North Atlantic from New England. Over the remainder of the weekend, Isaias is on track to fully transition into a mid-latitude system with a front extending south towards South Florida. The high over Texas will be sufficient to push the front over the Gulf and towards the Keys. Meanwhile, the Atlantic high will be able to build and maintain southeasterly breezes through tomorrow. The main source of uncertainty stems from what happens to the aforementioned front. Statistical models suggest it will pass across the Florida Keys by mid-week. The challenge stems from what happens to the winds and the dew points. Will dew points be able to decrease to near 70, or even the upper 60s? If so, how long will that last? Will there be a distinct wind shift and surge in wind speed? These questions will become more clear by the end of the holiday weekend. At the very least, the next couple of days will be free of nearby tropical cyclones.

MARINE

Issued at 225 PM EDT Sat Oct 10 2026 No watches, warnings, or advisories are in effect for the nearshore or offshore waters of the Florida Keys.

From synopsis: Enhanced swells generated by Post- Tropial Cyclone Isaias are steadily subsiding across the western waters of the Florida Keys. Breezes are slowly slackening to gentle to moderate breezes this weekend. Shower coverage will start to increase tonight as breezes back southeasterly to easterly. During the second half of the weekend, breezes are on track to back further northeasterly. Drier air will start to filter in on Sunday, and shower chances will drop below normal by the start of the work week. A frontal boundary associated with Post-Tropical Cyclone Isaias may push through the Florida Keys mid-week.

AVIATION

(18Z TAFS) Issued at 225 PM EDT Sat Oct 10 2026 The main concern at the beginning of the 18Z TAF period will be at EYW for southerly crosswinds. THe sustained wind direction between 160 and 170 may occasionally turn due south with sustained winds of 10 to 15 knots. This concern will diminish quickly, around 20Z as the wind direction will gradually back to the southeast, then east. Otherwise, no other significant concerns are forecast for either terminal. VFR conditions will prevail with only occasional MVFR CIGs after 11/00Z due to some light shower activity in the area.

CLIMATE

On this day on 2009, the daily record warm low temperature of 84F was recorded in Key West. Temperature records for Key West date back to 1872. Also, on this day in 1975, the daily record warm low temperature of 83F was recorded in Marathon. Temperature records for Marathon date back to 1951.

PRELIMINARY POINT TEMPS/POPS

Key West 80 89 79 88 / 60 20 10 10 Marathon 82 88 81 87 / 50 10 10 10

KEY WATCHES/WARNINGS/ADVISORIES

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