Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
548 FXUS62 KKEY 291736 AFDKEY Area Forecast Discussion National Weather Service Key West FL 136 PM EDT Fri Aug 29 2025 ...New AVIATION, PREV MARINE, DISCUSSION, AND FORECAST... .AVIATION... (18Z TAFS) Issued at 140 PM EDT Fri Aug 29 2025 Despite a current lull in convection in the vicinity of the terminals, additional scattered showers and thunderstorms are expected to form, then increase in coverage and intensity after 21z. Due to the chaotic nature of the convective evolution, have included a general period of VCSH in the terminals for now, with impacts to visbilities and ceilings to be left to expected requirement amendments with possible TEMPO groups. Outside of any storm, near- surface winds will generally be out of the east to southeast at near 5 knots, becoming variable at times. && .MARINE... Issued at 1115 AM EDT Fri Aug 29 2025 Although there is currently a convective lull across the Keys marine zones, additional scattered showers and thunderstorms are expected to flourish by the early afternoon hours. Any stronger thunderstorm will produce locally higher winds and confused seas. From synopsis, an early season Canadian high pressure system will continue to traverse across the eastern United States and move into the Atlantic over the next few days. This will allow for breezes to slacken through the weekend. Pressure gradient across the Gulf including Florida and the Florida Keys will increase early next week, resulting in freshening breezes. Moisture will increase as well, supporting higher shower and thunderstorm coverage through early next week. && .PREV DISCUSSION... Issued at 1115 AM EDT Fri Aug 29 2025 Arrived on the day shift four hours ago to see scattered showers and thunderstorms dotting the entire Florida Keys and adjacent coastal waters. Radar trends have since waned, with only isolated showers and thunderstorms now present in the Gulf waters north of the Lower Keys. This is expected to be a very short-lived lull. The 12z morning sounding at KEY highlighted an environment characterized by no inhibition, ample mixed-layer available potential energy to be realized, and deep tropospheric moisture. Surface synoptic analysis places a quasistationary front draped across Northern Florida, and a weak area of high pressure extending across the North Atlantic, with its axis somewhere near the Florida Space Coast. Water vapor imagery depicts a longwave trough encompassing the entire Eastern Seaboard. The lack of ridging, coupled with the deep moisture, and the fact it is nearing our annual convective maximum all supports well above normal rain and thunder chances today. No changes proposed to the inherited once-per-day full forecast package. && .FORECAST... Issued at 341 AM EDT Fri Aug 29 2025 Bottom line up front, the forecast is filled with uncertainty due to a very messy pattern. In the mid and upper levels a rather unusual, strong trough is moving across the eastern third of Canada and the U.S. At the surface, a weak low pressure system has developed off the coast of the Carolinas with a trailing frontal boundary stretching back across the Florida Panhandle and north Gulf Coast. Quickly filling in behind this boundary is an early season Canadian High pressure that is diving into the Great Lakes Region. This will slowly push the boundary southward and settle across the Central and Northern Florida area. As this occurs, the pressure gradient across the Keys will weaken such that winds may briefly go light and variable this afternoon and evening. On top of this, the low level ridge axis of the Atlantic Ridge lies just to our north, which is allowing moisture to gradually pool across the region. As we go into the weekend, the ridge axis will get shoved south as the upper level trough not only remains anchored along the Eastern Seaboard, but expands as it gets reinforced by multiple shortwaves rounding the base. As a result, the base of said trough will get closer to the Keys over the weekend and into early next week. Afterwards, shortwave after shortwave will pile up and pivot through this trough. Models agree that the trough will expand and broaden across the U.S. east of the Rockies. At the same time, high pressure will try and pivot north from the western Caribbean. Unfortunately (or fortunately, depending on which side of the fence), this will place the Keys in a somewhat active pattern. The combination of moisture continuing to pool over the area and the broad upper level trough just to our north, will result in slightly above normal rain chances. Have opted to take a middle of the road approach as the models differ wildly as to how rain/thunder chances will ultimately play out. There will be days that are wetter or dryer than others but given how messy and complex the upper level trough could become, it`s too soon to pinpoint those exact details. && .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 Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest