Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
508 FXUS62 KKEY 210710 AFDKEY Area Forecast Discussion National Weather Service Key West FL 310 AM EDT Fri Aug 21 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Rain chances will slowly increase throughout the weekend as SAL dust concentrations decrease. - Light and often variable winds suggest the environment may be favorable for waterspouts this afternoon. - Heat stress will remain a concern with highs in the lower 90s and dewpoints in the mid to upper 70s resulting in afternoon heat indices ranging from 105 to 108 degrees. && .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 259 AM EDT Fri Aug 21 2026 A split ridge pattern remains in place across the Florida Keys coastal waters. This will promote generally light to gentle SE breezes today, becoming variable at times during the afternoon, with a chance for thunderstorms in the southeastern Gulf. SE breezes will become more established over the weekend, freshening and becoming gentle to moderate at times during the overnight hours as Atlantic ridging builds slightly westward across the Bahamas. Rain chances will also slightly increase across the coastal waters this weekend in response to rising moisture content and subsiding SAL dust concentrations. && .AVIATION... (06Z TAFS) Issued at 259 AM EDT Fri Aug 21 2026 High pressure and weak flow over the region will promote VFR conditions at both TAF sites during this period. Sfc winds will exhibit more of a SE heading around 5 kts or less. Higher moisture content over the Southeastern Gulf may support convection during the morning hours (~10-14Z), but currently expecting development to remain N/NW of the terminals, so aviation impacts are not expected. && .PRELIMINARY POINT TEMPS/POPS... Key West 91 82 92 82 / 10 10 10 10 Marathon 90 82 90 82 / 10 10 10 20 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...DM Aviation/Nowcasts....DM Data Acquisition.....DM Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest