textproduct: Key West

KEY MESSAGES

- Windy conditions will continue across the Keys through Wednesday morning. Breezes will gradually slacken thereafter through late Thursday evening.

- Breezes will once again freshen Friday through early next week, with another period of windy and hazardous marine conditions for the Keys.

- Seasonal king tides combined with northeasterly winds will lead to coastal flooding through early next week, with the greatest impacts in the Upper Keys.

SHORT-TERM DISCUSSION

Issued at 858 PM EDT Tue Oct 20 2026 The 00Z RAOBs across the CONUS detected only minor mid-level height changes. Water vapor imagery detects a trough-ridge-trough pattern from the West to East Coasts, punctuated by a potent low pressure system southeast of New England. The 00Z KKEY RAOB sampled a 5 degC inversion based near 770 mb, composed of northeasterlies below the inversion and northwesterlies aloft. Over the next 24 hours, the ridge will sharpen over the Central US and Rockies, lower heights will race across the Great Lakes, and a short wave will amplify over the Gulf of America. Breezes will surge tonight as the Mainland exhales, followed by diminished breezes tomorrow morning. Rain chances will remain slight through the short term. No changes are needed or planned for the digital and derived forecast variables.

DISCUSSION

Issued at 120 PM EDT Tue Oct 20 2026 Surface analysis places a deepening low pressure system a few hundred miles east of the Outer Banks of North Carolina. Meanwhile in its wake, a 1032 mb high pressure system is parked in southeastern Canada. The interaction of these two synoptic features continues to produce breezy to windy conditions for the Florida Keys. The northeasterly breezes on the back side of the low pressure system is also acting to back up the Gulf Stream running along the Eastern Seaboard. Tides are elevated, particularly in the Upper Keys, where a Coastal Flood Advisory has now been issued. Local Doppler radar is only detecting a few isolated showers, mainly in the Upper Keys, with GOES-19 visible satellite imagery largely depicting mostly sunny skies across the Florida Keys and the adjacent nearshore and offshore marine zones. Cool advection around the continental high has caused temperatures to struggle a bit to recover today, with most island communities only hovering just above 80F at this early afternoon hour.

As the aforementioned low slowly progresses northeastward in the west-central North Atlantic and the high weakens, the pressure gradient gripping the Florida Keys will slowly weaken over the next 48 hours. With that said, the lull in breezes will be short- lived, as a second high dives from Canada southward towards the Mid- Atlantic. At the same time, there is growing global ensemble support for a plume of moisture associated with the front extending from the low in the North Atlantic then surging northward for late Friday through much of the weekend. There is also increasing support to suggest weak cyclogenesis occurring somewhere in the vicinity of the Bahamas late in the weekend. The ultimate evolution of this potential feature will have major implications on the rain and thunder chances for this period. Regardless, an extended period of windy conditions is nearly certain for Friday through early next week. Warm sea surface temperatures across the Keys will support efficient downward turbulent mixing of higher wind speeds aloft, with near- gales possible for a period late Saturday night through Monday.

If this wasn't complicated enough, persistent northeasterly strong breezes, combined with some of the highest seasonal predicted tides of the year, will support an extended period of coastal flooding concerns for the Keys, likely continuing into much of next week.

MARINE

Issued at 858 PM EDT Tue Oct 20 2026 A Small Craft Advisory remains in effect for all coastal waters of the Florida Keys due to northeast winds near 20 knots, and significant wave heights up to 7 feet in the Straits of Florida. From synopsis, a continental high pressure system centered over southern Canada will begin to weaken tonight and Wednesday, accompanied by slackening breezes. Another high pressure system will develop over the Eastern Seaboard Friday and Friday night. Meanwhile, a broad low pressure system will begin to fester near the southeastern Bahamas. The resulting pattern likely will result in strong, to potentially near gale breezes by Sunday or Sunday night. The freshening breezes and a surge of moisture will support elevated rain and thunder chances over the weekend.

AVIATION

(00Z TAFS) Issued at 858 PM EDT Tue Oct 20 2026 VFR and gusty northeast winds will prevail at the EYW and MTH terminals overnight.

KEY WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 6 AM EDT Wednesday for FLZ076.

GM...Small Craft Advisory until 6 AM EDT Wednesday for GMZ031>035- 042>044-052>055-072>075.