Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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902 FXUS62 KMFL 192314 AFDMFL Area Forecast Discussion National Weather Service Miami FL 714 PM EDT Thu Sep 19 2024 ...New UPDATE, AVIATION... .UPDATE... Issued at 706 PM EDT Thu Sep 19 2024 Convection has largely dissipated over the east coast metro early this evening, but it will take several more hours before activity wanes over the interior and SW FL. Guidance is hinting at lower ceilings and visibilities overnight into early morning, especially over the interior. Will add in patchy fog for now over the typical favored inland areas, and will need to monitor overnight. && .SHORT TERM... (Rest of today through Friday) Issued at 120 PM EDT Thu Sep 19 2024 Scattered to numerous showers will be likely across portions of South Florida this afternoon as as troughing prevails aloft and a front remains stalled over northern Florida. This is helping pool moisture over the region as evidenced by MLF`s 12Z sounding which showed PWATs of 2.02 inches, well above average for this time of year. The sounding also showed light sfc-3km westerly flow and ample instability (SBCAPE >2000 J/kg), along with light WSW flow aloft. Given this setup, expect afternoon sea breeze and outflow boundaries to become the focal points for deeper confection. The main concern for today remains heavy rainfall with slow moving storms which could lead to localized flooding for portions of South Florida. In fact, the HREF LPMM shows isolated areas along the East Coast metro possibly getting 4-6 inches of rain, and there are areas that have already received 2-4 inches of rain over the past couple of days, which has made for waterlogged soils. To that effect, WPC has placed most of the East Coast metro under a marginal (1/5) risk for excessive rainfall this afternoon. The frontal boundary will slowly drift southward across our region tomorrow, ushering in some slightly drier mid-level air over the area. This drier air mass could help limit shower and storm coverage tomorrow. However, with troughing lingering over the peninsula and light low level flow, there is still a chance for sea breeze driven convection to pick up tomorrow afternoon. We kept PoPs in the 40-50% range. Although temperatures and heat indices will remain above normal, convection and cloud coverage should help keep them below advisory criteria through the period. && .LONG TERM... (Friday night through next Wednesday) Issued at 209 PM EDT Thu Sep 19 2024 The mid-lvl trough axis will push through the area on Saturday, with low-lvl easterly flow becoming more established as sfc high pressure builds over the SE US. Although drier mid-lvl air behind the late week frontal passage will contribute to PWATs dipping near to just below climo (mostly 1.7 to 1.8 inches), seasonably cool temperatures aloft (around -7C at 500mb), combined with residual low-lvl moisture will support scattered showers and storms. The highest rain chances look to be over SW Florida given both the prevailing easterly flow and N-S moisture gradient. Mid-lvl ridging will then build into the SE US Sunday through early next week, with dry mid-lvl air, warm temperatures aloft, and general synoptic subsidence prevailing over SFL through at least Tuesday. Although the mid- lvl drying is quite evident, with PWATs dipping down into the 1.5-1.6 inch range over portions of the area, enough moisture remains in the low-lvls to support scattered showers and storms through the period. The highest rain chances, given the persistent easterly flow, would be over western portions of the Peninsula, and given the relatively stable airmass, deep convection may largely be limited to the southern third or so of the Peninsula (where instability is maximized). Towards the latter part of the upcoming workweek, forecast uncertainty increases as a portion of the Central American Gyre may consolidate into a more defined area of surface low pressure over the northern Caribbean or southern GOM. If this low consolidates further north or east it would (at the very least) likely draw deeper moisture towards the area which would naturally lead to higher rain chances. Conversely if the surface low forms over the Yucatan or SW Gulf (or doesn`t form at all), the drier ridge- dominated synoptic pattern would likely persist. It is important to note that these gyre setups in which there isn`t an extant disturbance are notoriously challenging to forecast. Consequently, particularly at these forecast lead times, the global ensembles provide a more complete picture of possible solutions compared to individual deterministic model runs, which will often display poor run to run consistency. Temperatures will likely remain just above seasonal normals with forecast highs in the upper 80s and lower 90s through the period. Although peak heat indices will likely reach the triple digits, somewhat lower dewpoints (mostly low to mid 70s) should preclude the issuance of heat advisories. && .AVIATION... (00Z TAFS) Issued at 706 PM EDT Thu Sep 19 2024 SCT thunderstorms will continue over interior and SW FL for several more hours this evening. Guidance is suggesting lower MVFR and possible IFR ceilings settling in overnight towards Friday morning, this will need to be monitored closely for further amendments. Light and variable winds through Friday morning and then becoming light east to northeasterly across the east coast metro and westerly at APF. SCT thunderstorms during the afternoon into early evening may result in brief flight restrictions and erratic winds. && .MARINE... Issued at 120 PM EDT Thu Sep 19 2024 Winds remain generally light across the coastal waters today as a weak surface boundary remains just to the north of the area, with continuing scattered to numerous showers and thunderstorms possible each day. The boundary reaches the area on Friday, bringing a decrease in thunderstorm activity through the weekend and into early next week. However, periods of locally higher seas and gusty winds may accompany any thunderstorm that forms. && .BEACHES... Issued at 120 PM EDT Thu Sep 19 2024 Expect minor to moderate coastal flooding to continue during periods of high tide. These elevated tides will continue to affect all coastal areas of South Florida through Friday morning, for which a coastal flood advisory remains in effect. For the upcoming weekend, a decrease in northerly swell should help reduce the risk for moderate flooding, but some minor flooding could still be possible. Additionally, an elevated risk of rip currents could continue for the Palm Beaches during the next several days. NAPLES HIGH TIDE TIMES... 1:56 PM today, 1:44 AM tomorrow morning, 2:57PM tomorrow afternoon LAKE WORTH HIGH TIDE TIMES...949 PM tonight, 10:24 AM tomorrow morning && .PRELIMINARY POINT TEMPS/POPS... Miami 75 89 76 90 / 60 50 40 40 West Kendall 74 90 74 91 / 50 60 40 50 Opa-Locka 75 90 75 91 / 60 50 40 40 Homestead 75 89 75 90 / 50 50 40 50 Fort Lauderdale 75 88 76 88 / 60 50 40 40 N Ft Lauderdale 76 89 77 90 / 60 50 40 40 Pembroke Pines 76 91 77 92 / 60 50 30 40 West Palm Beach 75 90 76 90 / 60 60 30 30 Boca Raton 75 90 76 90 / 60 60 30 40 Naples 77 90 75 92 / 30 40 20 30 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 5 PM EDT Friday for FLZ069-075-168- 172>174. AM...None. GM...None. && $$ SHORT TERM...ATV LONG TERM....Carr AVIATION...CMF