Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
920 FXUS62 KKEY 300854 AFDKEY Area Forecast Discussion National Weather Service Key West FL 454 AM EDT Mon Sep 30 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 340 AM EDT Mon Sep 30 2024 Water vapor imagery highlights a mean-layer ridge over the Western Caribbean, the southeastern Gulf, and the Bahamas. Meanwhile, there is a TUTT cell in the Central Caribbean and a lazy, positively tilted trough axis in the southern Plains. The nocturnally confluent east-southeasterlies and the northern extent of a moisture slug sparked scattered showers and isolated thunderstorms this morning. Most island communities are in the mid 80s with dewpoints in the upper 70s. The morning commute will include occasional downpours. .FORECAST... The forecast for today through Wednesday night remains rather straight forward. East to southeast steering will diminish somewhat as the moisture slug currently across the Keys exits stage west. Forecast soundings and time-height cross sections indicate very dry air (dewpoint depressions approaching 25 degC at 700 mb) will invade the lower tropospheric profile tonight through Wednesday. We continue to advertise a window (tonight through Tuesday night) of below normal rain chances for the island chain as the dry air limits moist congestus. These slight chances may need to be extended into Wednesday. The long term forecast for Thursday and beyond remains challenging. The first feature to track is a low-level cyclonic node noted east of Belize by the CIMSS analyses. This undulation in the easterlies will continue northwest into the southwestern Gulf of Mexico today through Thursday. Meanwhile, the TUTT cell moving west through the Central Caribbean will snarf low-level vorticity out of Columbia/Panama, which in some instances is rather dubious and a fictional bias. [It should be noted, the eastern flank of the TUTT currently has weak low-level cyclonic curvature according to CIMSS.] Nevertheless, the mid-week TUTT interaction appears to have some run- to- run and model- to- model consistency. By Thursday or Thursday night, lower mid to upper level heights in the Gulf of Mexico will now have multiple pieces of low-level vorticity to coalesce into surface pressure falls. The final evolution is leaning towards an escape across Florida between an upper trough axis over the Mississippi River Valley and ridging over the Greater Antilles. Complicating the forecast may be a last minute infusion of baroclinic forcing spilling out of the Appalachians. So, lots of uncertainty in the details for Thursday and beyond. Despite the murky details, the multi model MOS and NBM consensus points towards several days of above normal rainfall, and we advertise the same. The NHC gives this Gulf system a 50% chance of development into a tropical cyclone over the next seven days. && .MARINE... Issued at 340 AM EDT Mon Sep 30 2024 High pressure straddled across Florida will maintain gentle to moderate breezes across the Florida Keys today through Wednesday. Breezes may freshen for the Wednesday night through Thursday night time frame as an area of low pressure moves northwestward through the Western Caribbean into the Gulf of Mexico. Breezes are anticipated to slacken gradually for Friday and Friday night. && .AVIATION... (06Z TAFS) Issued at 340 AM EDT Mon Sep 30 2024 VFR conditions will prevail at both terminals through the TAF period with surface winds east to southeast at 5 to 10 knots. The very early morning hours will see some shower activity on radar, but opting to keep VCSH out of the TAFs after 12Z because these showers should be far enough away from both terminals. && .CLIMATE... On this day in 1945, the daily record low temperature of 69F was recorded in Key West. This is also tied for the coldest temperature ever recorded in September. Temperature records date back to 1872 in Key West. && .PRELIMINARY POINT TEMPS/POPS... Key West 90 82 90 82 / 40 20 20 20 Marathon 90 82 90 81 / 40 20 20 20 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...CLR 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