textproduct: Key West

KEY MESSAGES

- A strong pressure gradient associated with a cold front will support a prolonged period of windy conditions across the Florida Keys.

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

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

UPDATE

Issued at 917 PM EDT Sun Oct 18 2026 Latest SPC mesoanalysis shows a rather substantial PWAT gradient is in place across Florida with values as low as 0.3 inches in the northern portions of the state compared to the values around 2 inches or higher across the Florida Keys. This deeper moisture across the Keys allowed for repeated rounds of widely scattered to numerous showers and isolated embedded thunderstorms across the region, mostly across the Straits and at times near the island chain. Recent KBYX VAD wind profile data and the 19/00Z KEY RAOB shows a NE low-level wind flow regime in the post-frontal environment with quite breezy conditions as NE winds of near 30 kts were sampled just off the deck in the sounding data and were estimated even stronger in the VAD data, though the VAD data was likely a bit overdone. Regardless, the strong pressure gradient between a deepening low in the western Atlantic and high pressure in the mid-Atlantic and Northeast will keep the breezy NE flow and associated quick-moving shower activity streaming to the southwest across the Straits the remainder of the evening and overnight hours, which at times could also move across the island chain but PoPs will certainly be highest in the Straits. Rain chances will then slowly decrease from north to south into Monday as northerly flow aloft on the backside of the vertically stacked low in the western Atlantic brings drier air into the region, especially in the mid and upper levels. Overnight lows will be in the upper 70s with breezy conditions of 15-20 mph and occaisional gusts over 25 mph in island communities and values could reach special marine warning criteria at times over the waters and we will be monitoring trends closely.

DISCUSSION

Issued at 127 PM EDT Sun Oct 18 2026 A broad region of disturbed weather extends from the Bahamas west through the FL Straits towards northern Cuba along and ahead of a cold front which is draped nearly parallel over the Florida Keys. To our north and west, an expansive anticyclone is encompassing much of the eastern CONUS with water vapor imagery depicting deep layers of dry air advecting south into the Gulf and through the Florida Peninsula. Cloudy and windy conditions continue across the Keys and surrounding waters. Showers and thunderstorms are focused across the Florida Straits where deep tropical moisture is pooled ahead of the front. Surface and marine observations have been reporting continuous fresh to occasionally strong northeasterly breezes along the island chain and surrounding nearshore waters, supporting the ongoing Small Craft Advisory for all Florida Keys waters. High PoPs are forecast to remain focused across the Florida Straits where waves of showers and thunderstorms will occur through at least tomorrow. Chances decrease with northern extent, but passing showers and an occasional thunderstorm will be possible along the island chain through tonight. Activity near the Upper Keys has generally remained offshore, but we did see a slow moving thunderstorm affect the Key Largo area with radar estimated rainfall around 1.5". We'll need to keep an eye on redevelopment in that area which may lead to localized flooding.

A strong nor'easter is forecast to develop off the Carolina coast tonight while our cold front stalls in the Florida Straits. Persistent northerly mid to upper-level flow will eventually force the dry airmass south across the Keys during the day tomorrow and on Tuesday as the remnant front undergoes frontolysis and washes out. As such PoPs, will be on a gradual decline beginning tomorrow, and by Wednesday, our weather looks quite pleasant across the Keys. We may see several days with dewpoints in the 60s and highs in the lower to mid 80s. Despite decreasing PoPs, gradient winds will remain enhanced for the next few days, gradually slackening each day through the week with peaks at night and subtle lulls during the daytime. For now, expect the Small Craft Advisory to be needed for at least another day, perhaps two, due to fresh, occasionally strong northeasterly breezes leading to hazardous marine conditions.

MARINE

Issued at 127 PM EDT Sun Oct 18 2026 A Small Craft Advisory is in effect for all the Florida Keys waters. Widespread showers and embedded thunderstorms remain focused across the Straits of Florida this afternoon.

From synopsis, a cold front is situated nearly parallel to the Florida Keys waters with fresh to strong breezes occurring across the nearshore and offshore waters. Hazardous winds and seas are expected to continue through this afternoon, and a Small Craft Advisory is in effect for all the Florida Keys waters. The cold front is expected to stall across the Straits of Florida tonight. Expect fresh to strong northeasterly breezes to prevail through the first half of the week. Shower chances will gradually decrease by Monday as drier air begins to move in while the front is forced further south.

AVIATION

(00Z TAFS) Issued at 917 PM EDT Sun Oct 18 2026 Breezy NE winds are expected throughout the forecast period with occasional gusts of 25 kts at times. VFR conditions will mostly prevail, though occasional scattered SHRA may move across the island chain overnight, possibly bringing brief VSBY restrictions at times. This is a low chance but we will monitor trends to see if a AMD will be necessary. Rain chances decrease further on Monday, though some lingering SHRA still can't be ruled out.

KEY WATCHES/WARNINGS/ADVISORIES

FL...None. GM...Small Craft Advisory until 5 AM EDT Monday for GMZ031>035- 042>044-052>055-072>075.