Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
965 FXUS62 KKEY 210136 AFDKEY Area Forecast Discussion National Weather Service Key West FL 936 PM EDT Sun Sep 20 2026 ...New DISCUSSION, MARINE, AVIATION... .KEY MESSAGES... - Well above normal rain chances (around 60-70%) will persist across the Florida Keys through early this week. - Heavy rainfall is expected at times. There is a marginal risk for excessive rainfall through Monday morning. - While breezes will be light to gentle (5 to 10 mph), gusty winds and locally hazardous seas are expected in the vicinity of thunderstorms. && .DISCUSSION... Issued at 931 PM EDT Sun Sep 20 2026 Another messy evening has been unfolding across the Florida Keys this evening. Showers and thunderstorms have continued into the evening shift across all of our waters, and occasionally crossing the island chain. MRMS 6-hour rainfall estimates show that virtually all of the Keys saw rain to some degree this evening with rainfall totals generally between a few hundredths of an inch and just under one inch. However, the estimations across the Seven Mile Bridge are almost two inches due to a disorganized cluster of particularly heavier showers crossed around sunset. Were sure Fred the Tree was thrilled! We have talked a lot about an upper level low now centered just off of the SWFL coast, and this is the big player in our unsettled weather. The 00Z KKEY sounding from this evening calculated a PWAT value of 2.11, which is much closer to normal than where we were at twenty four hours ago. Dry slotting that was occurring within the lows set up helped to keep activity at bay yesterday, but we have lost some of its influence this evening. Instability was calculated to be just shy of 1800 J/kg with very little inhibition. Considering the amount of outflow boundaries out KBYX radar is currently detecting, shower activity doesnt look like it will diminish as we head into the overnight hours. Most of these showers are having difficulty in building tall enough for thunderstorms. While we have seen a handful of more robust thunderstorms during the afternoon, lightning detection has simmered down significantly. This may be due to the fact that most of the activity this evening has taken place near, and to the north of, the island chain. This area has been fairly worked over to some degree. Radar trends show new activity currently building over the Florida Straits, an area that has remained much less worked over. For that reason, well go ahead and continue to carry the showers likely with a chance of thunderstorms for the overnight hours. As newly developed activity may approach the island chain, anyone night owls may be able to hear a rumble of thunder, or two. No changes are proposed with this evening update. && .MARINE... Issued at 931 PM EDT Sun Sep 20 2026 There are no watches, warnings, or advisories in effect for the Florida Keys local waters. However, spotty shower and thunderstorm activity during the overnight hours may lead to localized hazardous marine conditions, including gusty and erratic winds, heavy downpours, and occasional lightning strikes. From synopsis, a wet weather pattern will persist across the Florida Keys coastal waters for the next several days as an upper- level low lingers in the eastern Gulf waters. As a result, the main hazards from scattered to numerous showers and thunderstorms will be a daily occurence with gusty winds, lightning strikes, blinding downpours, and locally hazardous seas. Breezes will generally remain light to gentle into the new week but brief periods of moderate breezes may occur in the evening hours. && .AVIATION... (00Z TAFS) Issued at 931 PM EDT Sun Sep 20 2026 VFR conditions should prevail at both island terminals through the TAF period, but a messy pattern consisting of disorganized showers and thunderstorms moving in variable directions could lead to occasional periods of MVFR of IFR CIGs at either terminal. Showers and thunderstorms are possible at virtually any given time throughout the TAF period, so opting for a broadbrush of VCSH with TEMPOs to address the timing for better chances of active weather onsite. Outside of this, surface winds will remain generally light and variable in this unsettled pattern, eventually assuming a southerly component. Cross wind concerns are low due to maximum sustained winds near 5 knots. && .KEYS WEATHER HISTORY... On this day, in 2005, Hurricane Rita passed 45 miles south of Key West as a category two hurricane. Key West recorded sustained winds of 62 mph and gusts to 76 mph. Marathon reported sustained winds of 41 mph and gusts to 52 mph. Flooding 2 feet above ground level flooded up to 4 blocks inland in midtown Key West. Up to 200 residences affected by storm surge in Key West. Storm tides estimated at 3 to 5 feet above mean sea level. Numerous coastal streets flooded with U.S. Highway One flooded at Sea Oats Beach on Lower Matecumbe Key. Rainfall totaled 4.26 inches at John Pennekamp State Park in Key Largo. && .PRELIMINARY POINT TEMPS/POPS... Key West 78 90 79 90 / 50 50 70 70 Marathon 80 88 80 89 / 60 60 70 70 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...DP Aviation/Nowcasts....DP Data Acquisition.....MJV Visit us on the web at weather.gov/key Follow us on Facebook and X at: www.facebook.com/nwskeywest www.x.com/nwskeywest