Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
682 FXUS62 KKEY 210902 AFDKEY Area Forecast Discussion National Weather Service Key West FL 502 AM EDT Fri Jun 21 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 500 AM EDT Fri Jun 21 2024 It is looking to a be a steamy start to Friday in the Keys this morning. Temperatures across the island chain are currently in the lower 80s with dewpoints in the mid to upper 70s. Offshore marine observation stations are reporting moderate easterly breezes that are notably lower in magnitude than the last few days. Convection has been somewhat sporadic across the Straits of Florida throughout the overnight hours, but a broken line of showers did pass through the Lower and Middle Keys a few hours ago. Currently, KBYX detects a few shallow cells popping up east of the Middle Keys and trekking west towards land. Despite meager shower coverage, most of the island chain is draped in a swath of high clouds that spiraled off of the northeast edge of the Central American Gyre (or CAG) planted on the Yucatan Peninsula. A weak low with some associated convection has snuck over the Bahamas to land just off the east coast of Florida. This places said feature in between the high pressure centered just north of Bermuda and the remnants of Tropical Depression Alberto over southern Mexico. As a result, the tight pressure gradient that had promoted fresh to strong breezes across south Florida earlier this week has slackened. Today and through this weekend, breezes will gradually lighten in response. This doesn`t mean we will lose the influence of the CAG as the prevailing east to southeast winds will draw a good deal of tropical moisture across the Keys. In fact, CIMSS MIMIC TPW currently depicts the island chain on the edge of a large moisture gradient with higher PW values observed in the Straits of Florida. With these features in place, today will be somewhat of a transitional weather day across our CWA. Moderate easterly breezes will start to bring in some of the previously mentioned moisture while pushing some of the continental dry air currently stuck over south Florida out of the way. While yesterday evening`s sounding had a PW value measured over 1.6 inches, there`s still some dry air mixed in that has kept most convection from reaching thunderstorm status. Throwing in decreasing speed convergence due to slackening winds and reduced surface heating due to high cloud cover will result in less favorable rain chances than one might infer from this set up. Opted to stay at a modest 40% PoP which is above climatology for this time of year but also less than what is to come. Tonight and the rest of the weekend, as the low in the western North Atlantic lands on the US coastline guidance continues to pump spokes of moisture over the area with signs pointing towards a period of wet, unsettled weather. Currently holding at 50% PoPs through this weekend, but some MOS guidance is in agreement for higher values Saturday. By the start of next week, high pressure in the Atlantic will wrestle control back over our winds and near normal PoPs are expected to return. && .MARINE... Issued at 500 AM EDT Fri Jun 21 2024 Small Craft Should Exercise Caution until winds decrease in the Straits of Florida and Deep Gulf waters. From synopsis, a weak low off the east coast of Florida has wedged itself between high pressure centered north of Bermuda and the remnants of Tropical Depression Alberto over southern Mexico allowing a slackening of of east to southeasterly breezes over the next few days. Moisture pulled into our area via the Central American Gyre will result in waves of unsettled weather this weekend. High pressure building over the North Atlantic early next week will result in light to gentle southeast to south breezes. && .AVIATION... (06Z TAFS) Issued at 500 AM EDT Fri Jun 21 2024 VFR conditions will prevail at the EYW and MTH terminals through Friday evening. Above normal rain chances are expected, however exact timing or coverage of convection will be difficult to forecast, so have included just VCSH throughout the TAF period for now. Short-term amendments will be issued as needed, based mainly on radar trends. Short periods of MVFR or even IFR conditions will be possible if convection directly impacts a terminal. Outside of any stronger convection, surface winds will remain from the east at 7 to 12 knots. && .CLIMATE... On this day in Keys weather history in 1986, an F1 tornado caused $250k in damage between Plantation and Tavernier. Tropical Storm Bonnie formed in the central Gulf moving westward on the 23rd, so this tornado may have been caused by the initial depression/circulation. && .PRELIMINARY POINT TEMPS/POPS... Key West 88 79 88 79 / 40 50 50 50 Marathon 88 80 88 80 / 40 50 50 50 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...JAM Aviation/Nowcasts....Jacobson Data Acquisition.....Jacobson Visit us on the web at weather.gov/key Follow us on Facebook and Twitter at: www.facebook.com/nwskeywest www.twitter.com/nwskeywest