Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
227 FXUS62 KKEY 301815 AFDKEY Area Forecast Discussion National Weather Service Key West FL 215 PM EDT Thu May 30 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 215 PM EDT Thu May 30 2024 A late morning and early afternoon cumulus cloud line in light and variable flow has struggled thus far, likely owed to relatively dry air sampled in the 925-850 mb isobaric layer in this morning`s 12z sounding at KEY. With that said, KBYX radar and visible satellite imagery is detecting outflow associated with earlier convection in the Florida Bay shooting southwestward towards the Lower Keys. We will see if this forced air parcel ascent can overcome the aforementioned dry air to generate a more coherent cloud line structure over the next several hours. Land- based surface observations support a seasonably warm and humid day across the island chain, with temperatures generally in the upper 80s to near 90F, and dew points in the lower to mid 70s. A weak shortwave trough observed in satellite imagery is expected to pivot towards the Florida Peninsula this evening. This should interact with low-level seabreeze boundary collisions to proliferate convection across the South Florida. Associated outflow boundaries should then propagate away from the convection, with some likely reaching the Bayside, Gulfside, and Florida Bay. Two limiting factors preventing convection from then reaching the island chain are the dry air as well as the lack of defined steering flow. Convective allowing model (CAM) mesoscale guidance supports this uncertainty, with varying degrees of shower activity this evening and in the early overnight hours. Ghost boundaries may persist, which may spark additional isolated showers in the overnight hours. Given these uncertainties, have maintained the inherited slight rain and thunder rain chances for the first period. A front draped over the Florida Gulf Coast will dive southward, pushing through the Florida Keys Friday afternoon. In its wake, a surface high with Canadian origins will drive a continental airmass into the Florida Keys this weekend through early next week. Global ensemble and statistical guidance has backed off somewhat on the dew point drops, but occasional dew points in the upper 60s to near 70F certainly don`t appear out of the question from appreciable boundary layer mixing owed to sea surface temperatures near 90F around the island chain. This same vertical mixing should result in breezy to near windy conditions this weekend, with Small Craft Advisories likely required for portions of the marine zones beginning as early as Friday evening. The front will linger south of the Florida Keys for the early to middle part of next week, keeping a sharp moisture gradient in the vicinity of the island chain. A series of shortwaves will progress across the Southeast, which will keep the climatological ridging relatively suppressed across the Florida Keys. Also, global guidance suggests a Central American Gyre (CAG) will strengthen in the central Caribbean, progressing northeastward towards the Lesser Antilles for this period. This should swing occasional slugs of moisture towards the Keys. Given these factors, elected to nudge PoPs slightly upward for these periods to elevated chance levels. Depending on ultimate cloud cover and rainfall coverage, temperatures should remain at or slightly below normal for these periods. && .MARINE... Issued at 215 PM EDT Thu May 30 2024 There are currently no watches, warnings, or advisories in effect across the Florida Keys. Light to gentle, occasionally variable breezes will gradually become easterly overnight. High pressure currently over the Ohio Valley will continue to dive southeastward, emerging off the Mid- Atlantic coast over the weekend. This will result in freshened northeast to east breezes beginning as early as Friday night, lasting through early next week. Small Craft Advisories may be required for portions or all of the Florida Keys marine zones for much of the weekend. && .AVIATION... (18Z TAFS) Issued at 215 PM EDT Thu May 30 2024 VFR conditions will prevail at both island terminals through the TAF period. Near surface winds are light and variable but will become 5 to 10 knots and easterly early this evening. Some shower activity could creep down the island chain from the mainland and near the MTH terminal but confidence in timing and likelihood will leave that out of the TAF for the time being. && .CLIMATE... On this day in Keys Weather History, a waterspout moved onshore as an F0 tornado along the north end of Duval Street in 1999. No damage was reported from this tornado. && .PRELIMINARY POINT TEMPS/POPS... Key West 92 81 91 80 / 10 20 20 20 Marathon 90 82 90 80 / 20 20 20 20 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...BT Aviation/Nowcasts....AP Data Acquisition.....AP Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest