Area Forecast Discussion
Issued by NWS Key West, FL
Issued by NWS Key West, FL
616 FXUS62 KKEY 110942 AFDKEY Area Forecast Discussion National Weather Service Key West FL 542 AM EDT Tue Jun 11 2024 ...New DISCUSSION, MARINE, AVIATION... .DISCUSSION... Issued at 542 AM EDT Tue Jun 11 2024 Convective activity has ramped up across the Florida Keys forecast area overnight. KBYX is detecting scattered light to moderate rainfall, with a few embedded heavier showers. Earlier, a strong thunderstorm moved across Carysfort Reef Light and produced a wind gusts of 46 mph. Winds have picked up a few knots higher than expected in the western coastal waters and across the Lower Keys, and the Sand Key C-MAN station is reporting gusts of 22 knots. The upcoming week is proving to be quite a tricky forecast, as evidenced by the lack of measurable rainfall in most island communities overnight. Last night`s sounding sampled all of the necessary parameters (i.e. high CAPE, virtually no inhibition, and well above normal moisture), but rainfall has been scarce along the island chain. This has likely been due to the diffluence across our area thanks to a low-level ridge axis extending across the Bahamas and South Florida. The diffluence at the surface can still be seen, with a southeast to south wind direction at Sand Key and a southwest wind direction at Carysfort. This ridging will be one of the factors causing the above normal uncertainty in the forecast over the next few days. Despite any uncertainties, the knowns in the forecast are pointing to a wet few days of weather for the Florida Keys. The generally synoptic set is a broad trough (Central American Gyre) pushing deep tropical moisture into the region for the remainder of the week. A stalled front, currently lingering along the Gulf Coast, will remain stalled with maybe a little southward movement through the week. This front will act to keep moisture trapped across the Gulf for a prolonged period. The Weather Prediction Center has placed the entirety of South Florida and the Florida Keys in a Slight Risk (level 2 of 4) of excessive rainfall today through Friday due to the extended stay of this tropical moisture plume. Now let`s talk uncertainties...As previously mentioned, winds have already jumped to above what was expected. Guidance suggests that these winds should start to decrease by this afternoon, so have issued a Small Craft Advisory for the western waters through at least later this morning. Just how far these stronger winds will extend eastward and their exact magnitude for the remainder of the day is a little fuzzy, and amendments to the wind forecast may be necessary if anything drastically changes. In terms of rainfall, model guidance is suggesting that we will become weakly confluent later this morning. This confluence combined with a forecasted 25-30 knot steering flow and well above normal PW should, in theory, lead to widespread rainfall. The best confluence will be to our north, so we could see a rather dramatic rainfall gradient across our area. This environment will generally remain in place through the end of the week, so have kept rain chances at likely to categorical (60-80%) through Friday. Have also decided to issue a Flood Watch for the entire Florida Keys with the expected rainfall. With the uncertainties involving stark gradient that will likely set up somewhere in our area, have only issued the Flood Watch through Wednesday night at this time. Depending on the evolution of the environment over the next 36 hours, this watch may need to be extended through the remainder of the week. By the start of the weekend, ridging will begin to build back in and shove the best moisture to our west. Rain and thunder chances will finally begin to diminish beginning on Saturday night, but will still remain slightly above normal through the extended forecast. && .MARINE... Issued at 542 AM EDT Tue Jun 11 2024 A Small Craft Advisory was issued for the western coastal waters including the western Straits, western Hawk, and Gulf waters including the Dry Tortugas. Elsewhere besides the Florida Bay, small craft should exercise caution until winds decrease. From synopsis, the pattern this week will feature weak high pressure over the western North Atlantic and a frontal boundary stalled over northern Florida. Although, the main weather maker will be a large cyclonic gyre centered over Central America. As such, moderate to fresh breezes and an extended period of unsettled weather featuring thundery squalls will persist today through Friday night. Rain and thunder chances will decrease gradually starting Saturday. && .AVIATION... (06Z TAFS) Issued at 542 AM EDT Tue Jun 11 2024 Showers and thunderstorms began developing in waters surrounding the Florida Keys before 7Z, but active weather transitions between VFR and potentially IFR conditions will dominate the TAF period. Current observations and hi-res model guidance suggests VCSH conditions at the terminals will begin before sunrise. Showers are expected to approach EYW and MTH in waves as a mixture of VCSH and VCTS throughout the TAF period. Expect rapid deterioration in flight conditions when heavy showers and lower CIGs move ashore. The timing the approach of individual thunderstorms is extremely uncertain, resulting in the absence of TEMPOs from the TAFs. Prevailing near- surface winds will remain southerly to later southwesterly within a range of 10 to 15 knots and gusts between 20 and 25 knots, but gusts may approach 35 knots near showers. && .CLIMATE... On this day in 1999 in Keys weather history, the daily record rainfall of 2.50" was measured at Key West. Local climate report says the rain fell in less than three hours, and the associated thunderstorms produced wind gusts of 50-60 mph that minor damage on Stock Island. Rainfall records for Key West date back to 1871. && .PRELIMINARY POINT TEMPS/POPS... Key West 88 79 87 80 / 80 80 80 60 Marathon 88 80 87 80 / 80 80 80 60 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through Wednesday evening for FLZ076>078. GM...Small Craft Advisory for GMZ033>035-044-054-055-074-075. && $$ Public/Marine/Fire...NB 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