Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
277 FXUS62 KKEY 131721 AFDKEY Area Forecast Discussion National Weather Service Key West FL 121 PM EDT Fri Sep 13 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 100 PM EDT Fri Sep 13 2024 The extended period of stagnant anomalously light and variable, stagnant flow continues for the Florida Keys and the adjacent coastal waters. Synoptic analysis places an upper-level trough centered over the Tennessee Valley associated with the remnants of Post Tropical Cyclone Francine. Closer to home, broad, anticyclonic flow is associated with a ridge centered somewhere in the vicinity of western Cuba. The 12z morning sounding at KEY highlighted an uninhibited environment with ample low-level moisture. However, meager steering flow continues to prevent any substantial showers and thunderstorms from developing thus far today at this early afternoon hour. With that said, there are signs of streamers north of the island chain beginning to percolate. Temperatures are hovering near 90F at most island communities, with heat indices in the mid-100s. Through the weekend and at least the first part of next week, the overall synoptic pattern will change little. This supports near- climatological rain and thunder chances, predominantly dominated by mesoscale processes, including diurnally-driven island cloud lines, outflow boundaries shooting off afternoon convection over the Florida Mainland, and residual boundary collisions. Outside of this activity, there will be ample solar insolation and elevated dew points to support continued heat indices peaking at or above Heat Advisory criteria for these forecast periods. The forecast becomes increasingly complicated and thus uncertain beyond the first of next week. There is increasing confidence that the aforementioned trough will amplify and slowly retrograde southward. This displacement will be primarily attributed to the influence of a strong blocking high over southeastern Canada. The ultimate placement and strength of this upper-level trough will have strong impacts on the sensible weather for the Florida Keys. Should the trough dive east of the Florida Peninsula, a drier air mass can be expected. However, should the trough dive towards the Gulf of Mexico, falling heights coupled with a plume of deep, tropical moisture would support several days of wet bouts. For now, it seems prudent to indicate broad- brushed elevated chances beyond Monday, emphasizing changes to this extended forecast are quite likely. Stay tuned. && .MARINE... Issued at 100 PM EDT Fri Sep 13 2024 A Coastal Flood Statement remains in effect for the Florida Keys. Ponding on the typically favored roadways will peak at the times of the morning higher high tide in the Lower and Middle Keys, with little tidal cycle relief in the Upper Keys. Other than these minor coastal flooding hazards, are no watches, warnings, or advisories in effect for the Florida Keys coastal waters. From synopsis, light at times variable breezes will continue through Wednesday across the Florida Keys coastal waters. The remnants of Post- Tropical Cyclone Francine will continue to decay over the Tennessee Valley, with westerly swells from Francine subsiding across the western Keys marine zones overnight. A frontal boundary will slowly slide southward and potentially stall near or just north of the Florida Keys starting late Monday. This could bring higher rain and thunder chances back to the region, although the extended forecast is highly uncertain. && .AVIATION... (15Z TAFS) Issued at 100 PM EDT Fri Sep 13 2024 Variable breezes and VFR conditions prevail for EYW and MTH. Near surface breezes dropped to near 5 knots with periods of light and variable speeds. Clouds are pulsing just north of the Lower and Middle Keys which may cause short-lived periods of VCSH or MVFR CIGs near the terminals. Cloud cover will decrease after sunset. && .CLIMATE... On this day in Keys weather history, in 1987, the record warm-low of 86F was last recorded in Marathon. This is also tied as the warmest low temperature recorded during the month of September. Climate observations for Marathon date back to June 1950. && .PRELIMINARY POINT TEMPS/POPS... Key West 83 92 83 91 / 30 30 30 30 Marathon 83 91 83 91 / 30 30 30 30 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory until 7 PM EDT this evening for FLZ076>078. GM...None. && $$ Public/Marine/Fire...BT Aviation/Nowcasts....AJP Data Acquisition.....AJP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest