Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
634 FXUS62 KKEY 131857 AFDKEY Area Forecast Discussion National Weather Service Key West FL 257 PM EDT Sat Sep 13 2025 ...New AVIATION... .AVIATION... (18Z TAFS) Issued at 255 PM EDT Sat Sep 13 2025 VFR conditions are expected at both EYW and MTH for the rest of the day, but while rain chances have decreased showers still cannot be fully ruled out at either terminal. If enough convection develops on mainland Florida, outflow could spark showers and storms near the island chain, especially near MTH, later this evening. As there is low confidence in the exact timing and location of this event no mention is in either TAF at this time. Near surface winds will continue to be generally out of the north at 5 to 10 knots. && .PREVIOUS DISCUSSION... Issued at 1147 AM EDT Sat Sep 13 2025 A relatively quiet morning continues on for the Florida Keys after last night`s active period. Surprisingly, partly cloudy skies are observed on GOES-19 visible imagery as cloud debris from last night`s mesoscale convective system (MCS) shifts over the Bahamas and out of our waters. Meanwhile, some high clouds are still present due to persistent showers in the distant Straits of Florida, but are quickly deteriorating. KBYX radar also detects some showers percolating along boundaries extending through the Deep Gulf waters and over across the Middle Keys, though lightning has been more absent then not. As this boundary pushed over the Upper and Middle Keys, gentle northeast breezes backed to the north across our eastern offshore observation stations along the Reef. A similar separation of temperature values is also seen on land as observations on the Upper Keys are reading in at around 81 degrees with the rest of the island chain being a few degrees higher. Dewpoints are still floating about the mid 70s. Uncertainty prevails in the short term forecast period as a few environmental features are presenting differently than originally expected. The front that had been rooted over mainalnd Florida for so long has sunk south over our waters towards Cuba taking away a possible source of synoptic lift. Meanwhile, the upper level trough axis is still nosed over the Yucatan Peninsula displacing upper level support for convective development out towards the Bahamas rather than encompassing our waters. The most surprising feature is drier air descending along the west coast of Florida. While this morning`s KKEY 12z sounding was not particularly dry, a land shadow is present off of the southwest coast of mainalnd. TBW`s 12z sounding is is quite dry this morning above the surface with northerly winds advecting more dry air near the lower levels and pushing it down the coastline. These factors plus the fact that the overnight MCS arrived when it did, explains the lull in activity we are currently observing. That being said, some convection is still trying to bubble in the Gulf, particularly along boundaries located outside of the path of the old MCS. Will keep PoPs where they are with the high end of guidance as there are certainly enough ingredients around for wet season to do its thing before drier air fully seeps in. && .FORECAST... Issued at 430 AM EDT Sat Sep 13 2025 Confidence in the forecast beyond today remains quite low. While the upper-level trough will slowly lift northeastward, global ensemble numerical weather prediction (NWP) mean products suggest the surface boundary will continue to flirt with the Keys through the work week. As the surface high north of the boundary strengthens and builds southward, the pressure gradient will likely increase, supporting freshening easterly breezes. Where the moisture gradient associated with the boundary ends up in relation to the Keys will determine measurable rain chances. Current NWP products suggest drier periods Monday night into Tuesday, before a return to elevated rain and thunder chances for Tuesday night and beyond. Temperatures will remain seasonably warm, with highs in the upper 80s to near 90, and lows in the upper 70s to near 80. && .MARINE... Issued at 1147 AM EDT Sat Sep 13 2025 No watches, warnings, or advisories are currently in effect for the coastal waters of the Florida Keys. From synopsis, a weak frontal boundary will remain in the vicinity of the Florida Keys coastal waters over the next several days. Weak undulations of this feature, interacting with high pressure to its immediate north, will result in a low confidence forecast for winds and rain chances. Gentle to moderate northeast to east breezes are expected to build in by Tuesday or Wednesday, as the axis of the high pressure finally is able to spread down closer to the Keys marine zones. && .PRELIMINARY POINT TEMPS/POPS... Key West 78 89 79 90 / 50 40 40 40 Marathon 78 88 79 89 / 50 40 40 40 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...JAM Aviation/Nowcasts....JAM Data Acquisition.....JAM Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest