Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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913 FXUS62 KMFL 251145 AFDMFL Area Forecast Discussion National Weather Service Miami FL 745 AM EDT Wed Sep 25 2024 ...New AVIATION... .SHORT TERM... (Today through Thursday) Issued at 302 AM EDT Wed Sep 25 2024 *** KEY POINTS FOR TROPICAL STORM/HURRICANE HELENE *** Impacts for South Florida: Helene, soon to be a hurricane, will bring about heavy rain, gusty winds, storm surge (Gulf Coast), and increased flooding potential as its outer bands move across the region. A Tropical Storm Warning is in effect for Collier, Glades, Hendry, and Mainland Monroe counties. Flood Watch Issued: A Flood Watch is in effect for all of South Florida, as rainfall amounts of 2-6 inches are possible across inland and metro areas. Storm Surge Risk: 2-4 feet of storm surge is expected along the Gulf Coast from Bonita Beach to Flamingo due to Helene`s size and the shallow Florida shelf. Values as high as 5 feet may be observed. A Storm Surge Warning is in effect for these coastal areas. Limited Tornado Threat: Tropical tornado risk is limited but a few tornadoes may spawn Wednesday night into early Thursday, especially along the southwest Florida and the Lake Okeechobee region. The focus remains on Tropical Storm Helene, which is expected to strengthen into a hurricane as it moves over the northwestern Caribbean Sea, just offshore from the Yucatan Peninsula. South Florida is already experiencing the effects of the storm, as evidenced by high precipitable water (PWAT) values exceeding 2.2 inches, dew points in the upper 70s, and warm air aloft. Outer bands from Helene are expected to move northward across the region today, bringing periodic heavy rain with intervals of sunshine. Winds from the southeast will strengthen throughout the day, with gusts exceeding 30 mph, especially along the coasts. The primary impacts from Helene will arrive late Wednesday as the storm center progresses northward through the Gulf of Mexico. A significant moisture envelope will move into the region during this time, with PWAT values forecasted between 2.3 to 2.5 inches - nearing climatological highs for late September. Models also indicate a long, skinny CAPE profile, supportive of warm cloud processes and heavy rainfall. Given these parameters, there is potential for heavy rain and localized flooding across the area. A Flood Watch is in effect for Collier, Glades, and Hendry counties from Wednesday morning through Friday, with the possibility of extending eastward depending on rainfall accumulation earlier today. Rainfall amounts between late Wednesday and Friday evening are expected to range from 2 to 4 inches inland, with metro areas potentially seeing 3 to 6 inches. Several advisories remain in effect for the Gulf Coast, including a Tropical Storm Warning and a Storm Surge Warning from Bonita Beach to Flamingo. Storm surge may reach 2-4 feet, with some vulnerable coastal areas possibly seeing up to 5 feet due to the large size of Helene and the shallow nature of the Florida shelf. Dangerous marine and boating conditions will prevail across the entire region, with the most significant impacts felt in the Gulf waters. As Helene`s outer feeder bands move across the region, tropical storm-force wind gusts are possible throughout South Florida. Aside from the risks of storm surge, flooding rains, and wind, the threat of tropical tornadoes appears limited. South Floridas residence time within the northeast quadrant of the system could reduce the window for tornadic activity, with the peak risk for tornadoes between 18Z-00Z due to dry air mixing and diurnal heating. Tornado potential may be confined to coastal areas of Collier, depending on the storm`s track. A second window for possible tornadogenesis may open in the Lake Okeechobee region Thursday afternoon as Helene moves further north in the Gulf of Mexico. Temperatures will remain near climatological norms, as cloud cover and widespread rain keep highs in check. Rainbands will bring gusty winds, intense rainfall, and localized urban flooding throughout the day. The brunt of the storm`s impacts will begin this afternoon and continue through the night, with rainbands lingering through Thursday as the system`s trailing edge moves through the area. && .LONG TERM... (Thursday night through Tuesday) Issued at 302 AM EDT Wed Sep 25 2024 Helene will have made landfall along the Big Bend/Gulf Coast region of Florida by late Thursday, and its direct impacts will be distant from South Florida. However, a stream of elevated moisture, characterized by PWAT values of 2.3-2.5 inches, will continue to drape over the region as breezy southwesterly flow persists. This southwest flow, associated with Helene`s extratropical transition, could enhance low-level convergence, further elevating hydrologic concerns, especially in areas prone to poor drainage. The moisture fetch will likely linger into the weekend, keeping humidity levels high across South Florida. Through the weekend, South Florida will experience a transitioning weather regime. Initially, low-level steering flow will come from the south and southwest, but it is expected to gradually shift to the west and northwest over time. The stream of moisture will become more diffuse, but enough will remain to produce scattered showers and thunderstorms. Localized flooding may occur, but overall impacts should be minimal. Looking beyond the weekend, some long-range models suggest the potential for a weak frontal passage, bringing a light northwesterly flow. However, it is too early to confirm this, and the event remains uncertain given its distance in time. && .AVIATION... (12Z TAFS) Issued at 741 AM EDT Wed Sep 25 2024 Brief periods of MVFR conditions this morning as SCT showers and thunderstorms move across South FL. Coverage will increase as the day goes on as Tropical Storm Helene enters the SE Gulf of Mexico. E/SE winds around 10 kts early this morning will increase to 15-20 kts with gusts of 25-30 kts by this afternoon and continue through the remainder of the period. Flight restrictions will be likely again this afternoon and tonight during periods of heavy rain. Conditions will deteriorate early morning tomorrow as Helene`s bands move over the area, with sustained winds up to 20 kts and gusts up to 40 possible after 16Z and restrictions likely to prevail through the day. && .MARINE... Issued at 302 AM EDT Wed Sep 25 2024 Moderate easterly winds will gradually increase in magnitude as Tropical Storm (soon to be Hurricane) Helene approaches the Gulf waters. Winds and seas will become dangerous across the local waters as the system intensifies and moves northward. Tropical Storm conditions are likely across all the local waters, and the most dangerous conditions will occur across the Gulf waters. Numerous to widespread showers and thunderstorms will generally be observed by midday today into Thursday. && .BEACHES... Issued at 302 AM EDT Wed Sep 25 2024 Moderate to major coastal flooding can be expected over the Gulf coast late Wednesday into Thursday as Tropical Storm Helene strengthens and tracks through the SE Gulf of Mexico. Strengthening onshore flow will result in an extended period of high rip current risk over the east coast (likely through the work week), with potentially hazardous surf developing over the Palm Beaches in the mid-week period. Additionally hazardous beach conditions look likely over the Gulf coast beaches starting Thursday as surf increases in association with Tropical Storm Helene. && .PRELIMINARY POINT TEMPS/POPS... Miami 89 80 89 80 / 70 70 70 70 West Kendall 89 79 89 80 / 70 80 70 70 Opa-Locka 89 80 89 81 / 70 70 70 70 Homestead 89 80 88 80 / 70 80 70 70 Fort Lauderdale 88 79 89 80 / 70 70 70 70 N Ft Lauderdale 89 80 90 81 / 70 70 70 70 Pembroke Pines 90 81 90 81 / 70 70 70 70 West Palm Beach 89 79 90 80 / 80 60 70 60 Boca Raton 89 79 90 80 / 80 60 70 70 Naples 90 79 87 82 / 80 80 90 80 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Tropical Storm Warning for FLZ063-066>075-168-172>174. Flood Watch through Friday morning for FLZ063-066>075-168- 172>174. Storm Surge Warning for FLZ069-075. High Rip Current Risk through Friday evening for FLZ168-172-173. High Surf Advisory from 11 AM this morning to 8 PM EDT Thursday for FLZ168-172-173. AM...Tropical Storm Warning for AMZ610-630-650-651-670-671. GM...Tropical Storm Warning for GMZ656-657-676. && $$ SHORT TERM...SRB LONG TERM....SRB AVIATION...ATV