Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
962 FXUS62 KKEY 191859 AFDKEY Area Forecast Discussion National Weather Service Key West FL 259 PM EDT Sun May 19 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 300 PM EDT Sun May 19 2024 It has been another hot and steamy afternoon across much of the Florida Keys as Day 3 of the heat continues. KBYX radar has been quiet much of the day and GOES 16 Visible satellite imagery shows mostly fair weather cumulus clouds throughout the Keys. Some of these clouds earlier oriented themselves into a cloud line along the Island Chain. This cloud line started to the north and has since been slowly drifting southward to a place south of Island Chain. The Lower Keys is where this cloud line remains mostly over land still. Temperatures along the Island Chain are in the upper 80s to lower 90s with the Big Pine Key RAWS coming in with 94 degrees this afternoon. Dew points are in the upper 70s to near 80 degrees. As a result, the hot temperatures combined with the humidity is making the heat index which is what it feels like when you step outside to be in between 105 to 110 degrees. Therefore, the Heat Advisory remains in effect until 6 PM EDT this evening for heat indices up to 110. The deep mean layer ridge continues to loosen its grip on the region as it moves to the southeast and further away from the area as a weak frontal boundary slides down the Florida Peninsula. As a result, marine platforms are observing southwest to west winds of 5 to 10 knots with the Upper Keys near 10 mph. The Lower and Middle Keys are observing west to northwest winds near 10 mph. .FORECAST... The mean layer ridge that has been dominating the weather across the Keys for the last few days will continue to move off to the southeast. Therefore, the heat we have been experiencing for the last few days is about to take a break. Upper level troughing over the Southeast coastline and just offshore will continue to slowly slide southward as it impinges on the aforementioned ridge. At the surface is a weak frontal boundary draped across central Florida and out into the central Gulf of Mexico. This front is currently responsible for the ongoing convection across east-central Florida, south of the Space Coast along with another area of convection over the southeastern Gulf to the northwest of the Florida Keys. This boundary will continue to slide southward tonight resulting in no change to the previous forecast. 40% PoPs were maintained for the overnight period with the only change being to add scattered thunder to the eastern Straits of Florida. Hi-res model guidance has also been very consistent on showers and thunderstorms developing in the vicinity of the Keys around 20/06z overnight with the bulk of this activity remaining south of the Island Chain. The aforementioned upper level trough and corresponding weak area of low pressure over the Northwestern Bahamas is expected to keep the Keys unsettled for early to mid week. Therefore, no change was made to the forecast either for Monday through the Tuesday night time frame. Kept the PoPs the same as the previous package with 30% Monday, 40% Monday night, 30% Tuesday and 20% Tuesday night. The most likely driver for convection after tonight will be residual outflow boundaries from previous convection along with some daytime destabilization to help ignite new rounds of showers and thunderstorms. Wednesday through the upcoming holiday weekend, upper level ridging will begin to move back into the region, though, not as strong as this previous ridge. Drier air moves back in resulting in slight chances (20%) being maintained through the period. Temperatures look to remain in the upper 80s to near 90 degrees with dew points lower than they have been as of recent with mostly lower to mid 70s expected. && .MARINE... Issued at 300 PM EDT Sun May 19 2024 There are currently no watches, warnings, or advisories in effect across the Florida Keys coastal waters. From synopsis, the western extent of a low-level ridge axis that extends west- northwest continues to loosen its grip across the Florida Keys, and breezes have shifted to the southwest to west. Breezes will quickly veer to the north while further decreasing tonight as a frontal boundary slides down the Florida peninsula. There may be a break in the rain-free conditions tonight through Tuesday, followed by variable breezes. Wednesday through the end of the week, breezes will peak and lull with northeast to east breezes in the afternoon and evening and then east to southeast during the overnight and morning hours. && .AVIATION... (18Z TAFS) Issued at 300 PM EDT Sun May 19 2024 VFR conditions will prevail at EYW and MTH the remainder of this afternoon through midnight. Near-surface winds are beginning to slacken to near 5 knots and may become variable during the TAF period. Cloud bases will lower overnight as scattered showers and isolated thunderstorms develop near and along the Florida Keys, per hi-res guidance. Uncertainty in the TAF centers around the exact timing of showers, if showers will be closer to EYW or MTH, where or when thunderstorms will develop near the island terminals, and if showers over the islands will be sufficient to generate IFR conditions. && .CLIMATE... Yesterday, May 18th, the low temperature at both Key West and Marathon was 84F. This broke daily record warm low temperatures at both sites. At Marathon, this low temperature tied the highest warm low ever recorded in May in Marathon (current record that was tied: 84F, 2017), and broke the highest warm low ever recorded in May in Key West (previous record: 83F, 2024, 2020, 2017). Temperature records date back to 1872 in Key West and 1950 in Marathon. && .PRELIMINARY POINT TEMPS/POPS... Key West 80 88 79 89 / 40 30 40 30 Marathon 80 89 79 90 / 40 30 40 30 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory until 6 PM EDT this evening for FLZ076>078. GM...None. && $$ Public/Marine/Fire...MJV Aviation/Nowcasts....AJP Data Acquisition.....DR Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest