textproduct: Key West

KEY MESSAGES

- Very warm and humid conditions will continue across the Florida Keys, raising the risk for heat-related illnesses through the weekend. - Rain and thunder chances will be increasing starting tonight and peaking Sunday through Monday.

- Breezy conditions are possible by early next week.

DISCUSSION

Issued at 1020 AM EDT Sat May 16 2026

For the near-term this afternoon, the morning sounding confirmed some airmass modification is underway with a veering east-to-south wind profile is helping to pivot a relatively higher precipitable water axis northward. Indeed mixed layer CAPE is nearly double from the same time Friday morning, and other derived parameters such as convective temperature dropping. Aloft northwesterlies continue as a shortwave trough remains to our east with an upper ridge axis over the western half of the Gulf of America. Modest height rises were occurring at all levels, and despite the increase in moisture in the lower troposphere, mid-level temperatures have warmed about 1C, and the cumulus developing outside the office has remained of the fair weather variety. BYX 88D indicates two areas of isolated showers, with one area south of Dry Tortugas and another persisting with occasional deeper convection near the Cay Sal Bank.

This afternoon, the atmosphere is more apt to support convection, offset by what is likely to be a lee-Cuba shadow with descent spreading across the western half of the Straits. Still, a corrider along the north edge of the relatively higher moisture content from the Cay Sal Bank to the west-northwest could provide a conduit for a few showers and thunderstorms, and given the warm and moist lower troposphere, possible lee-side convection northwest of the Lower Keys.

Still, the continued northward drift of the moisture axis will favor scattered convection over water with better potential for a thundery downpour here and there along the Keys tonight. Along with the light southerly steering flow, that's where the higher rain chances will stay temporally for now.

MARINE

Issued at 1020 AM EDT Sat May 16 2026 Currently, east to southeast breezes were lightest along the Gulfside of the lower Keys at 5 to 10 knots, but a steady 9 to 12 knots along the Reef. Significant wave height was measured at 1 foot at 3 to 4 seconds at Satan Shoal. Light to gentle breezes will prevail this afternoon through Saturday. High pressure developing over the Southeast will take root across the western North Atlantic over the weekend. As a result, moderate to fresh easterly breezes will peak and lull across the Florida Keys Sunday through Tuesday.

AVIATION

(12Z TAFS) Issued at 1020 AM EDT Sat May 16 2026

VFR conditions with east to southeast breezes 7 to 11 knots are expected this afternoon at EYW and MTH and likely continuing through the evening. The chance for a passing vicinity shower or isolated thunderstorm increases during the early morning hours Monday, thus VCSH was inserted after 17/0800Z.

PREVIOUS DISCUSSION

Issued at 446 AM EDT Sat May 16 2026

A high pressure cell moving into the Atlantic off the Carolinas is beginning to exert it's presence across the Florida Keys. This has resulted in winds clock around from the east and southeast and gradually increasing through the overnight. Meanwhile, moisture is slowly pushing back this morning in thanks to a southeast to south mean flow in the boundary layer. This has begun interacting with a lingering boundary out across the Straits of Florida where isolated showers and thunderstorms have developed over the past couple of hours.

As the high continues to build across the Atlantic, we expect winds to continue to strengthen through the day. Meanwhile, the low-level steering flow will initially becoming increasingly southerly. This flow is not a favorable wind direction for all day shower potential. We will see some showers this morning with the initial surge of moisture and instability but then quiet by the late morning and afternoon. The exception will be the Upper Keys, where winds will be more southeasterly and more favorable to keep scattered showers and isolated thunderstorms going at times.

As the high slides further east, the steering flow will become southeast allowing for better moisture transport and increase our rain chances overnight through Sunday. The high's position by Sunday night through Monday night will allow breezes to peak and we can expect a brief period of breezy conditions. This will also aid in mass/moisture convergence and rain chances look to peak Sunday night into Monday. Thereafter, the high will continue to slide further east out across the Atlantic and the pressure gradient will relax some. In addition, pockets of drier air will pivot through at times, leading to a generally drying trend for the second half of next week.

No air mass changes expected. Daily high temperatures will range from 85 to 90 degrees and could be a couple degrees warmer late in the week. Dew points will hold in the mid 70s, the combination of which will result in heat index values hovering around 100 degrees during the peak daytime heating.

KEY WATCHES/WARNINGS/ADVISORIES

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