Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
644 FXUS62 KKEY 191434 AFDKEY Area Forecast Discussion National Weather Service Key West FL 1034 AM EDT Sun May 19 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 1030 AM EDT Sun May 19 2024 Today is Day 3 of the heat wave for the Florida Keys with the hot and tropical conditions continuing. KBYX radar remains quiet this morning with GOES 16 Visible satellite imagery showing some low level fair weather cumulus clouds moving from southwest to northeast across the easternmost portions of the Florida Keys. With plenty of sunshine out there again today, temperatures along the Island Chain are in the mid to upper 80s already. Some isolated locations are already recording 90 degrees at this hour, namely Big Pine Key and Boca Chica Key. Dew points are also very oppressive in the upper 70s to near 80 degrees. This is making the heat index across many island communities feel like it is in the 100s already and its just about half past 10 am. As a result, a Heat Advisory is in effect from 10 AM EDT this morning until 6 PM EDT this evening for heat index values up to 110 degrees. Deep mean layer ridging remains in place across the Keys, though, today we are on the northwestern periphery of the ridge as this ridge begins to slide further off to the southeast as a weak frontal boundary slides down the Florida Peninsula. Due to this, marine platforms around the Keys are observing south to southwest winds near 10 knots with Island Chain communities observing near 10 mph. .SHORT TERM FORECAST... The 12z sounding this morning is beginning to show better signs for it to potentially rain here in the Keys. However, the sounding still shows dry layers which may continue to inhibit any potential shower/thunderstorm development today. There is one inversion present around 925 mb with another one just above 800 mb. While we are starting to see a moistening profile, the dry layer between 925 mb to approximately 850 mb is concerning to get any substantial growth to the clouds through the area currently. If we can get a significant trigger that can help to raise the air parcels then we might be able to punch through this layer to cause showers/storms to form. However, that doesn`t appear likely at least during the day. That might change tonight as the weak frontal boundary sliding down the Florida Peninsula gets closer. There is also a decent veering profile to the sounding, albeit, light winds. Also, there is plenty of instability with CAPE coming in over 3000 J/kg! Moisture is also sufficient with the PWAT measured to be 1.80 inches. While we have most of the ingredients coming together, we continue to lack at least one and that one today is the trigger again. Therefore, no changes expected to the ongoing forecast. && .MARINE... Issued at 1030 AM 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 has begun to loosen its grip across the Florida Keys, and breezes have shifted to the south to southwest. Breezes will quickly veer to the north while further decreasing this afternoon 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 turning to the east Wednesday through Thursday. && .AVIATION... (15Z TAFS) Issued at 1030 AM EDT Sun May 19 2024 VFR conditions will be the predominant weather at EYW and MTH today and into the early evening hours. A slight chance for showers will remain today, but the lack of confidence in location and timing resulted in VCSH being absent from the TAFs. Overnight, near-surface winds are forecast to shift westward and slacken to near 5 knots. Scattered showers and isolated thunderstorms are forecast along the Keys, but hi-res guidance is showing activity developing overnight, therefore, VCSH may be added for the overnight to Monday morning time frame with the 18z TAF. Occasional MVFR CIGs will linger across EYW and MTH this morning as early morning cloud decks dissipate. && .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 91 80 88 79 / 10 40 30 40 Marathon 91 80 88 79 / 10 40 30 40 && .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.....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