Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
186 FXUS62 KKEY 210829 AFDKEY Area Forecast Discussion National Weather Service Key West FL 429 AM EDT Thu Aug 21 2025 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 429 AM EDT Thu Aug 21 2025 It has been a generally calm night across the Florida Keys until as of recently. KBYX radar was void of any radar returns until the last hour or so. Isolated showers have developed along a residual mesoscale boundary from earlier convection just off the Upper Keys. Another area of isolated showers has also formed across the westernmost Straits of Florida due south of the Dry Tortugas. GOES East Nighttime Microphysics imagery shows mostly clear skies throughout the Keys with the exception of where the shower activity has developed where we see cumulus congestus and stratocumulus. Also, in just the last half hour, we now have thunderstorms observed just off the Upper Keys and across the westernmost Straits as the clouds were able to grow tall enough to generate lightning. It has also been a very warm overnight with summer in full swing as we move into late August. Temperatures along the Island Chain are in the mid 80s with dew points in the upper 70s. Hurricane Erin continues to move off to the north northeast early this morning with the storm centered just east of North Carolina. Weak ridging from the Atlantic to the south of Erin is also trying to nudge its way westward into the Keys. Due to the expansive nature of Erin and the Keys on the northwestern side of the weak ridge, marine platforms are observing southwest to west breezes of 5 to 10 knots. Island Chain communities are observing near 5 mph. .FORECAST... Outside of Hurricane Erin, the forecast for the next several days to week or more looks to remain rather benign. Hurricane Erin remains the main story for the next day or so as it is currently making its closest pass to the Eastern Seaboard. The storm will continue to move north northeastward before turning more northeastward by tonight while accelerating as it moves farther out into the North Atlantic. This will result in another day or two of southwest to west breezes. The Keys remain well to the southwest of Erin and are located to the northwest of the weak ridge trying to build in behind Erin across the southwestern Atlantic. Moisture is expected to remain rather plentiful again for today with GOES East Total Precipitable Water (TPW) products showing PWAT values of 1.7 to 2.0 inches across the Keys. Therefore, 30% PoP was maintained. However, the only real trigger we have to get any shower or thunderstorm activity are leftover mesoscale boundaries from earlier convection and potentially some very minor speed convergence today. There is also the potential for reverse cloud lines for the next few days as the pattern remains quite stagnant and winds remain light. This is typically a good pattern for cloud lines and waterspouts. We will keep an eye on this closely over the coming days. Other than that, weak ridging will build into the Keys for Friday continuing through the weekend and even much of next week. Slightly drier air is expected to move in for the weekend and next week resulting in 20% PoPs through the extended. Otherwise, the summertime heat and humidity will be the name of the game going forward with daytime highs in the lower 90s and overnight lows in the lower to potentially mid 80s. Heat index values will be consistently between 105 to 108 degrees each day. && .MARINE... Issued at 429 AM EDT Thu Aug 21 2025 There are currently no watches, warnings, or advisories in effect across the Florida Keys coastal waters. From synopsis, Hurricane Erin will continue to move to the north northeast today. The system will turn to the northeast by tonight moving away from the Eastern Seaboard and out into the North Atlantic while accelerating. A slight swell from the north will continue to lead to elevated seas in eastern portions of the Florida Straits for another day or two. A weak subtropical high pressure ridge will begin to build into the Keys tonight before settling over the Keys through the weekend. This will result in generally light, occasionally light to gentle breezes. && .COASTAL FLOOD... A Coastal Flood Statement remains in effect for all the Florida Keys. Tides are running almost a foot above predicted. As a result, minor saltwater flooding of low elevation streets and lots is likely. Some storm drains will overflow, and some seawalls and docks will be overtopped. Boaters can expect less clearance under fixed bridges. Motorists should remember that persistent puddles around the times of high tide are almost certain to contain a mix of saltwater. && .AVIATION... (06Z TAFS) Issued at 429 AM EDT Thu Aug 21 2025 VFR conditions will prevail at both island terminals through the TAF period with southwest to west surface winds of 5 to 10 knots. Mentions of showers and thunderstorms are not in the current TAFs due to low confidence related to timing and impact, but this will have to be reevaluated for future packages due to expected afternoon activity in the forecast area. The most likely impact from any nearby activity will be MVFR CIGs due to increased cloud cover. && .CLIMATE... On this day in Keys weather history, in 1973, the daily record cold high temperature of 81F was recorded. This is also tied for the coldest high temperature ever recorded in August. Temperature records for Key West date back to 1872. && .PRELIMINARY POINT TEMPS/POPS... Key West 92 83 92 83 / 30 20 10 20 Marathon 93 83 94 83 / 30 20 20 20 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...MJV Aviation/Nowcasts....DP Data Acquisition.....DP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest