Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
925 FXUS62 KKEY 211432 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1032 AM EDT Fri Aug 21 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Light and often variable winds suggest the environment may be somewhat favorable for a cloud line and associated waterspouts this 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. && .DISCUSSION... Issued at 1030 AM EDT Fri Aug 21 2026 Surface analysis highlights a weak pressure pattern across the Florida Keys. One area of high pressure remains parked in the western Gulf, with another high pressure system extending across the North Atlantic. The resulting surface wind vector summation of these features supports light generally southerly breezes across the Florida Keys and the adjacent nearshore and offshore coastal waters. GOES-19 visibile satellite imagery is detecting debris cirrus decks advecting southward towards the Keys from earlier deep convection across the southeastern Gulf. Closer to the surface, there is evidence of a Cuban shadow advecting northward in the Straits of Florida. Land-based surface observations indicate temperatures in the upper 80s at this late morning hour across the Island Chain. For the rest of today, the nebulous flow pattern may result in winds becoming variable for a time across the Keys during the afternoon hours. This would tend to support yet another round of island cloud line development. However, confidence in winds going variable is not as high as it was yesterday. Furthermore, the 12z morning sounding at KEY sampled a somewhat drier moisture profile between 925-850 mb, suggesting convective growth may struggle a bit today. Finally, low-level steering flow may remain strong enough to cause the Cuban shadow influence to reign supreme at convective suppression. Given all of these factors, low-end slight rain and thunder chances (around 10%) still seems reasonable. No changes proposed to the inherited overnight full forecast package. && .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. && .AVIATION... (15Z TAFS) Issued at 1030 AM EDT Fri Aug 21 2026 VFR conditions will prevail at both Florida Keys island terminals through 12z Saturday morning. The best chance for any isolated vicinity shower will be this afternoon and early evening due to possible island cloud line formation. Chances for development are low, 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. && .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...BT Aviation/Nowcasts....BT Data Acquisition.....BT Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest