textproduct: Key West

KEY MESSAGES

- A cold frontal passage across the Florida Keys today will usher in a prolonged period of windy conditions along the island chain.

- A Small Craft Advisory is in effect for all coastal waters for increasing winds and seas. These conditions will last through the next several periods.

- Shower chances will decrease during the early part of the week as a dry air mass approaches the Florida Keys.

DISCUSSION

Issued at 410 AM EDT Sun Oct 18 2026 A potent cold front moved over the Florida Keys waters last night. Showers and thunderstorms were able to flare along boundaries ahead of the frontal system. Surprisingly, shower coverage during the overnight hours has been less than expected given the GOES- East derived total PWAT after midnight was still in excess of 2 inches. That does not mean the radar has been inactive. Two thunderstorms north of the Dry Tortugas were able to develop clear, long-lasting rotation after midnight. However, these showers were likely the most intense cells we will observe during the cold frontal passage. The front did slow as it made its way south towards the Keys and it is likely to stall somewhere over the Florida Straits later this afternoon.

Early season cold fronts almost always result in a complicated forecast. Even though a drier air mass is on its way to the Keys, the cold front has lost a considerable amount of baroclinicity. Even though one can see a dry air mass moving into northern Florida on water vapor satellite imagery, it will take a few days for dew points drop from the mid 70s to near 70. The amount of moisture in the environment will remain high. Thus, even though atmospheric conditions are not as favorable for widespread showers, we are opting to keep 60 percent PoPs today and 50 percent tonight. Windy conditions are likely given the fresh to strong breezes along the reef and north of the Lower Keys. After months of dew points in the upper 70s, a drop into the lower 70s will be much appreciated.

MARINE

Issued at 410 AM EDT Sun Oct 18 2026 A Small Craft Advisory is in effect for all the Florida Keys waters.

From synopsis: a cold front is slowly moving southeast across the Florida Keys waters. Breezes freshened rapidly to fresh to strong breezes over the Gulfside waters before sunrise. Squally conditions are possible through this afternoon. A Small Craft Advisory is thus in effect for all the Florida Keys waters. The cold front is expected to stall somewhere over the Straits of Florida early this week. Expect fresh to strong northeasterly breezes to prevail through the first half of the week. Shower chances will gradually decrease tonight and Monday.

AVIATION

(06Z TAFS) Issued at 410 AM EDT Sun Oct 18 2026 A cold frontal passage across the Florida Keys will result in prevailing MVFR CIGs across the Florida Keys. CIGs near FL015 and FL020 are expected, though periodic breaks of VFR CIGs are possible. Near surface winds freshened to 15 to 20 knots with frequent gusts in the pre dawn hours. VCSH conditions are expected to linger before sunrise, but shower coverage is on track to decrease during the afternoon. A second pulse of SHRA is possible near sunset ahead of a wind surge coming off the peninsula.

PRELIMINARY POINT TEMPS/POPS

Key West 86 76 86 76 / 70 50 40 20 Marathon 85 77 85 76 / 70 50 40 20

KEY WATCHES/WARNINGS/ADVISORIES

FL...None. GM...Small Craft Advisory until 11 PM EDT this evening for GMZ031>035- 042>044-052>055-072>075.