Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
813 FXUS62 KKEY 290741 AFDKEY Area Forecast Discussion National Weather Service Key West FL 341 AM EDT Fri Aug 29 2025 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 341 AM EDT Fri Aug 29 2025 What started out as a quiet overnight has now blossomed with showers and thunderstorms over the last couple of hours. Most of the activity is developing in-situ over the island chain and across our norther waters. The distant Straits out by Cay Sal Bank is beginning to come to life with additional activity. Meanwhile, winds have become light from the southeast at 5 mph or less. Across the marine platforms we are hovering near or just above 5 knots. 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. && .MARINE... Issued at 341 AM EDT Fri Aug 29 2025 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. && .AVIATION... (06Z TAFS) Issued at 341 AM EDT Fri Aug 29 2025 Scattered showers and thunderstorms will develop around the island chain throughout the day, but confidence is low in the exact timing and placement near either terminal thus no extended mention is made in either TAF at this time. Near surface winds will be light out of the east to southeast. && .CLIMATE... On this day in Keys weather history in 1965, the daily record cold high temperature of 81 was recorded at Marathon. This is also the coolest high temperature ever recorded in the month of August. Temperature records for Marathon date back to 1950. && .PRELIMINARY POINT TEMPS/POPS... Key West 93 81 92 82 / 50 50 50 40 Marathon 91 81 91 82 / 50 50 50 50 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...LIW 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