092 FXUS62 KMFL 080740 AFDMFL Area Forecast Discussion National Weather Service Miami FL 340 AM EDT Fri Oct 8 2021 ...Unsettled Weather Pattern to Kick Off the Weekend... .SHORT TERM (Today through Saturday)... The synoptic pattern is shifting as a mid-level trough approaches the eastern Gulf of Mexico today. Abundant tropical moisture remains over the region with precipitable water values around or just above 2 inches. The deepening moisture through the layer along with the approaching trough will allow for increasing shower and thunderstorm chances as the diurnal sea breeze pattern develops with the interior spine of the peninsula serving as a primary target for boundary collisions on Friday afternoon. Some convective activity could linger through the evening before the mid and upper level trough axis approach the western portions of the peninsula which could lead to some overnight activity lingering over Southwest Florida and the Lake Okeechobee region heading into Saturday. With the upper level trough comes an associated jet that will push across South Florida early on Saturday as the trough axis amplifies over the region. As Saturday begins, we see the mid and upper level trough axis somewhere near Southeast Florida along with a low level frontal boundary extending in from the Atlantic (possibly with a surface area of lower pressure around coastal North Carolina) as well. This will permit for cooling temperatures aloft, height falls over the region, and the enhancement of convection that does develop along the convergence boundary somewhere in the vicinity of the Atlantic coast of South Florida. One concern is heavy rainfall which could lead to localized flooding, particularly on Saturday. There is also the potential for more stout convection with the cooler temperatures aloft, abundant surface moisture, and the dynamical support aloft thanks to the trough and associated jet structures. Instability should not be a concern with surface heating and -10 deg C temperatures at 500 mb providing some decent lapse rates. Cloud cover doesn't appear to be quite the mitigating factor, especially if the day starts off clear or mostly clear. Looking at all these factors, the potential for strong thunderstorms looks to exist on Saturday with even the non- zero chance for some severe storms. The primary concerns would be strong wind gusts and hail. When factoring some of the shear captured in model sounding hodographs, tornadic activity cannot be ruled out either. Overall, temperatures remain warm with most areas reaching the upper 80s to lower 90s again today before cooling a few degrees into the mid to upper 80s on Saturday. .LONG TERM (Saturday Night through Thursday)... Saturday night and Sunday: The mid-upper level trough will cut off as a closed low on Sunday just north of Grand Bahama Island with the associated trough axis over the Gulf Stream. At the surface, the frontal boundary will move over South Florida and likely stall and start becoming diffuse over the area on Sunday. Showers and thunderstorms will move mainly offshore over the Atlantic waters late Saturday night as drier air moves in for Sunday in the wake of the mid/upper trough. As a result, rain chances decrease some on Sunday, most notably across the Palm Beaches to the Lake Okeechobee area, but will keep 30-40% PoPs to account for some lingering low level moisture and cold temperatures aloft. If the drier air becomes more entrenched, PoPs may eventually need to be lowered some over the Palm Beaches, Lake Okeechobee area, and Gulf coast. Temperatures are forecast to be a few degrees lower (lows in the mid 60s to lower 70s and highs in the mid to upper 80s), but still near early October normal values. Monday through Thursday: Models are in generally good agreement in the cut-off mid/upper level low pressure lingering over or near South Florida Monday and Tuesday, then moving south into the Straits of Florida Wednesday and Thursday. Differences in the models exist mainly in the exact location of the mid/upper low relative to South Florida, which will play a role in where the deeper moisture will reside during this time frame. The GFS has the low right over the peninsula with the edge of the deeper moisture east of the low impinging on our area especially by mid-week, while the ECMWF has the low just offshore over the Atlantic and has a little drier air over the peninsula. Little change in PoPs was made from the previous forecast, keeping them in the 30-40% range as a good blend of the possible solutions. A GFS-like scenario would probably require higher PoPs, especially Wednesday and Thursday as deep layered NE-E wind flow increases, but we still have time to make adjustments as needed. Temperatures will trend a touch higher during this period, with lows mainly in the upper 60s to mid 70s, and highs in the upper 80s. && .AVIATION(06Z TAFS)... Generally VFR through the period with a lull in convection overnight and through much of the morning. Showers and storms will develop again in the afternoon and evening with a focus north and west with PBI and APF seeing the highest chances of sub-VFR impacts. Any terminal impacted by convection could fall to IFR/LIFR. Short-fused AMDs may be necessary. Also cannot rule out some patchy fog tonight, though chances are too low to mention. && .MARINE... Persistent light to moderate easterly to southeasterly winds will continue to support generally benign marine conditions today, with isolated to scattered showers and thunderstorms possible. For this weekend, increasing coverage of showers and storms is possible ahead of a stalling frontal boundary. A small 1 to 2 ft long period swell will also move into the Atlantic waters off South Florida on Saturday. && .BEACHES... A moderate rip current risk remains for the Palm Beaches today. Higher than normal astronomical tides (King Tides) could result in minor coastal flooding of vulnerable low-lying coastal areas during the times of high tide this week, though generally light winds and low surf heights should largely mitigate these concerns. An elevated risk of rip currents is possible for the east coast beaches this weekend as a small long period swell moves into the Atlantic waters. && .PRELIMINARY POINT TEMPS/POPS... Miami 89 76 88 73 / 40 20 70 60 West Kendall 91 75 89 70 / 40 20 70 50 Opa-Locka 90 76 89 72 / 40 20 70 60 Homestead 89 74 87 70 / 30 20 70 60 Fort Lauderdale 88 76 87 73 / 40 30 70 60 N Ft Lauderdale 88 76 87 73 / 40 30 70 60 Pembroke Pines 89 76 87 71 / 40 20 70 60 West Palm Beach 89 74 87 71 / 50 30 70 60 Boca Raton 89 76 87 72 / 50 30 70 60 Naples 89 74 87 72 / 50 40 60 40 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && $$ Today through Saturday and Aviation/Marine...RAG Saturday Night through Thursday...Molleda Visit us at weather.gov/miami Follow us on Facebook and Twitter at: www.facebook.com/nwsmiami www.twitter.com/nwsmiami