textproduct: Key West

KEY MESSAGES

- Conditions remain somewhat favorable for an island cloud line and associated waterspouts through late afternoon.

- Rain and thunder chances will return to near normal over the weekend through early next week.

- With highs near 90 and dewpoints in the mid to upper 70s, afternoon heat indices will peak at 105 to 108 degrees.

AVIATION

(18Z TAFS) Issued at 130 PM EDT Fri Aug 21 2026 VFR conditions will prevail at both Florida Keys island terminals through 18z Saturday afternoon. The best chance for any isolated vicinity shower will be late afternoon and early evening due to possible island cloud line formation, mainly in the vicinity of EYW. Chances for development are low due to a current BKN cirrus deck, although this will be monitored over the next several hours. Near- surface winds will generally be light out of the southeast to south through the TAF period, although winds will go VRBL at times through this evening.

PREV DISCUSSION

Issued at 259 AM EDT Fri Aug 21 2026 The Florida Keys will remain within a weak flow pattern today characterized by a split ridge orientation divided by deep-layer troughing over the Southeastern US. The center of the col region will shift slightly to our west in response to a subtle westward jog of the surface ridge over the Bahamas which will promote more of a southeasterly component to our winds today, especially across the Middle to Upper Keys and surrounding coastal waters. Nonetheless, expect generally light SE breezes becoming variable at times during the afternoon. Waterspout potential should not be quite as high as it was yesterday given less variability in the wind profile, but will still need to monitor cloud line development this afternoon due to the weak flow, particularly near the Lower Keys. The nearly 2" PWATs sampled by the 00Z KKEY RAOB would suggest ample support for routine showers and thunderstorms, but latest hi-res forecast soundings suggest an arriving pocket of drier low-level air will drop PWATs back down into the 1.4-1.6" range along the Island Chain while deeper moisture content will be found over the Southeastern Gulf. I have maintained a chance for thunderstorms in the Gulf with models suggesting scattered development in the 10-14Z time frame.

Heading into the weekend, a cold front associated with the aforementioned trough over the Southeast will advance south and stall along the Gulf Coast region as the trough axis becomes oriented along the Eastern Seaboard. SAL dust concentrations over the Keys will become mostly negligible as moisture pools ahead of the frontal boundary, and 1000-500mb RH values will, at times, range from 60-70% as southeasterly flow becomes more established. As such, expect a seasonable August forecast over the weekend with near-normal rain chances and hot and humid conditions. Highs in the lower 90s and dewpoints in the mid to upper 70s will result in continued heat stress and afternoon head indices in the 105-108 degree range.

MARINE

Issued at 1030 AM EDT Fri Aug 21 2026 Conditions will be somewhat favorable for island cloud line formation, mainly in the vicinity of the Lower and Middle Keys. Any cloud line may produce a few waterspouts. Mariners are reminded that a waterspout would most likely appear beneath a dark, flat bottom of a building cumulus line, just at the hint of rain.

From synopsis, a split ridge pattern remains in place across the Florida Keys coastal waters. This will promote generally light to gentle southeast to south breezes today, becoming variable at times during the afternoon. As North Atlantic ridging builds westward, southeasterly breezes will become more established over the weekend, becoming gentle and at times moderate during the overnight hours, continuing through early next week.

PRELIMINARY POINT TEMPS/POPS

Key West 91 82 92 82 / 10 10 20 10 Marathon 90 82 90 82 / 10 10 20 20

KEY WATCHES/WARNINGS/ADVISORIES

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