554 FXUS62 KMFL 061348 AFDMFL Area Forecast Discussion National Weather Service Miami FL 948 AM EDT Wed Oct 6 2021 .UPDATE... A few isolated showers over the Atlantic waters and east coast this morning. Dry air in the mid-levels will continue to limit overall shower and thunderstorm coverage. The dry air is depicted on the MFL 12Z sounding with a PWAT of 1.5 inches and can be seen over the region in mid-level water vapor satellite. However, there is enough low-level moisture to support isolated to scattered showers and storms this afternoon and evening. Convection will develop along the sea breezes, with highest chances over the interior and Gulf coast. Continue to monitor the tidal gauges at Naples this morning for departures from predicted levels. Currently, tidal levels are running about 0.5-0.6 feet above normal. This would keep tidal levels below minor flooding stage . However, minor flooding may be very isolated to low- lying areas or beaches along the SW Florida coast. No major changes from the previous forecast && .PREV DISCUSSION... (Issued 727 AM EDT Wed Oct 6 2021) AVIATION(12Z TAFS)... Mainly VFR conditions with east to southeasterly flow through the period, with a southwesterly wind shift expected at APF with Gulf breeze this afternoon. Isolated to scattered showers and storms along both east and west coast sea breezes, with the highest coverage over the interior and Gulf coast during the afternoon. Brief MVFR cigs/vis will be possible with convection. Winds relax overnight with E/SE flow remaining. PREV DISCUSSION... (Issued 310 AM EDT Wed Oct 6 2021) SHORT TERM (Today through Thursday)... Water vapor imagery shows a closed mid/upper-level low centered over portions of the lower Mississippi Valley, with a quasi-stationary attendant frontal boundary draped across the central Gulf of Mexico. The warm/moist conveyor belt associated with this system will remain displaced to the west of the Florida peninsula today (Wednesday), while dry midlevel air -- reinforced by the subsident-side of a low- level trough lifting northwestward from the Bahamas -- persists across the area. This dry midlevel air will continue to limit convective updraft development to an extent today (especially over the eastern half of South Florida), though ample boundary-layer moisture (lower/middle 70s dewpoints) combined with daytime heating and sea breeze development will support isolated to scattered showers and thunderstorms this afternoon. The greatest coverage will be over the interior and Gulf coast, where diurnal destabilization and low-level confluence related to the Gulf breeze will be maximized owing to prevailing easterly winds. By Thursday, the above-mentioned low pressure system will begin phasing with the mid-latitude westerlies and gradually lifting north- northeastward across the middle Mississippi Valley. This evolution will support modest downstream midlevel height falls and a related poleward low-level mass flux over the SE CONUS and eastern Gulf of Mexico -- gradually drawing deeper tropical moisture (PWs near 2.0 in) northward across the region from the western Caribbean Sea. This poleward moisture transport could also be aided by the previously mentioned low-level trough lifting toward the Carolinas coast, where it will merge with a weak effective warm frontal zone. Regional and high-resolution model guidance differ somewhat on the quality of the returning moisture and related buoyancy generation across South Florida, though a modest increase in shower and thunderstorm coverage can be expected -- especially across the western half of South Florida where the richer moisture will be in place along with a deeper Gulf sea breeze circulation. With increasing PW values and a deep warm cloud layer, locally heavy rainfall from slow-moving convection along the Gulf breeze will become a concern across the Gulf coast metro areas. Temperatures will be slightly above average through the short term period, with highs in the upper 80s to near 90 and lows in the middle to upper 70s. These warm temperatures combined with increasing dewpoints will result in maximum apparent temperatures climbing into the upper 90s to near 100 each afternoon. LONG TERM (Thursday Night through Tuesday)... A mid-level cut off area of low pressure transits towards the Great Lakes region before being absorbed back into the mid-level flow over eastern Canada this weekend. An associated surface trough will extend south from the southeastern United States across the Gulf of Mexico into the Yucatan region. Deepening moisture over southern Florida from the Caribbean and tropical Atlantic will linger through the weekend which will permit shower and thunderstorm chances each day. The mid-level trough will amplify southward into the state this weekend allowing convective activity and coverage to increase late Friday through Saturday. Heavy rainfall and more stout convection are concerns this weekend. Some spread begins to develop in the guidance by Sunday with regards to the timing of the trough axis pushing east into the Atlantic waters with high pressure attempting to build in at the mid-levels over the eastern Gulf in some solutions while other solutions are a bit slower to push out the moisture. Accordingly, Sunday could start wet and unsettled but could become drier (particularly in Southwest Florida) depending on the timing and location of the trough and if a dry slot of air materializes near the region. Uncertainty remains early next week as the unsettled pattern could remain though confidence is lower due to the location of the potential trough features at both the mid-levels and surface along with the associated moisture having some spread in the guidance. Drier air could reach the eastern Gulf of Mexico which could lead to some potential for lower convective coverage, particularly in Southwest Florida. MARINE... Persistent light to moderate easterly winds will continue to support generally benign marine conditions this week, with isolated to scattered showers and thunderstorms possible each day. A surface trough is forecast by the National Hurricane Center to lift northwestward from the Bahamas toward the Carolinas coast this week, supporting increasing shower and thunderstorm activity over the Atlantic waters off South Florida late this week. For this weekend, an additional increase in showers and thunderstorms is forecast as a midlevel disturbance approaches the area from the southeastern United States. At the same time, a small (1 to 1.5 ft) long period swell emanating from a distant low pressure system over the northern Atlantic waters is expected to move into the Atlantic waters off South Florida by around Saturday. BEACHES... A moderate risk of rip currents continues along the Palm Beaches today. Additionally, higher than normal astronomical tides (King Tides) could result in minor coastal flooding around the times of high tide this week, though generally light winds and low surf heights should largely mitigate these concerns. The rip current risk could increase once again for the east coast beaches this weekend as a small long period swell moves into the Atlantic waters off South Florida. && .PRELIMINARY POINT TEMPS/POPS... Miami 79 89 78 89 / 20 50 10 50 West Kendall 77 91 76 91 / 20 50 20 50 Opa-Locka 78 90 78 90 / 20 50 10 50 Homestead 77 88 76 89 / 20 50 20 40 Fort Lauderdale 79 88 78 89 / 20 50 10 50 N Ft Lauderdale 80 89 78 89 / 20 50 10 50 Pembroke Pines 77 88 77 89 / 20 50 10 50 West Palm Beach 77 89 77 89 / 20 50 20 60 Boca Raton 78 89 78 89 / 20 50 10 50 Naples 76 91 76 89 / 30 60 30 60 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && $$ Update/Aviation...Kelly Today through Thursday and Marine...Weinman Thursday Night through Tuesday...RAG Visit us at weather.gov/miami Follow us on Facebook and Twitter at: www.facebook.com/nwsmiami www.twitter.com/nwsmiami