Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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173 FXUS62 KJAX 241913 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 313 PM EDT Tue Sep 24 2024 ...TROPICAL STORM HELENE IMPACTS BEGINNING AS EARLY AS WEDNESDAY NIGHT... ...New NEAR TERM, SHORT TERM, LONG TERM, MARINE, HYDROLOGY... .NEAR TERM... Issued at 310 PM EDT Tue Sep 24 2024 For the latest NE FL and SE GA Daily Key Messages please visit: https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf Clear skies and easterly winds will continue tonight, with lows falling into the lower to mid 70s tonight. Regarding Tropical Storm Helene, a Hurricane Watch remains in effect for the I-75 corridor, and a Tropical Storm Watch for eastern Marion county. && .SHORT TERM... (Wednesday through Thursday night) Issued at 310 PM EDT Tue Sep 24 2024 Tropical storm Helene will be lifting northward over the northwest Caribbean and then the Gulf of Mexico Wed morning and early aftn, with some acceleration northward. Based on the NHC forecast, the system will be tracking northward Wed night and Thursday morning, and basically paralleling the FL west coast during midday Thursday as a Cat 2 to 3 and then making a landfall around the FL Big Bend Thursday evening. Slight adjustments to track are expected through the duration of the event, especially given the current state of the system being in the formative stages of development. For sensible weather on Wednesday, a few bands of showers will likely be ongoing by midday Wednesday with surface winds also increasing from the southeast. Some rotation in some showers possible but overall not too favorable just yet for tornado potential but will need to monitor closely. We could see some favored areas for a rotating shower/storm along the coastal counties where instability would be higher. Wed night, precipitation becomes more widespread with some better potential for rotation in some cells given the increasing shear, but again instability will be pretty lacking for any robust shower or storm that would produce a tornado, and, if any, appears to be across the coastal counties primarily. Rainfall amounts Wed will mostly be confined to northeast FL, but probably near or below 1 inch. Wed night, rainfall amounts are more widespread at about 1-2 inches and a few locales of 2-3 inches. Thursday, tropical system Helene is forecast to be over the east central Gulf of Mexico in the morning and be heading north-northeast about 16 mph but picking up a little forward speed northward. The landfall is projected to be in the evening. Tropical storm conditions will be possible for many counties as the pressure gradient associated with this system. Hurricane conditions possible over the far western counties and watches are already in place. There will be an elevated tornado threat for most of the area being in the favorable eastern semicircle of the cyclone, and sufficient instability given dewpoints in the lower to mid 70s. Additional rainfall amounts Thursday look to be in the 1-3 or 2-4 inch range. Thursday night, Helene forecast to track northward over the FL Big Bend with strong winds raking across portions of the area and Tropical storm conditions likely, and potential hurricane conditions mainly west zones. The winds should diminish toward the early morning hours. Key Message to Remember: Review your plans and ensure necessary supplies are assembled in the event of tropical storm or hurricane impacts later later this week. Please pay close attention to the forecast information locally as well as from the National Hurricane Center to stay abreast of the latest forecast information. && .LONG TERM... (Friday through next Tuesday) Issued at 310 PM EDT Tue Sep 24 2024 Helene will continue to quickly leave the region with a residual trough over the area southwest to northeast. Much lower rain chances are anticipated. Flow will be southwesterly and initially dry air Friday but moisture begins to advect back in from the south and southwest leading to enhanced chances of showers for the weekend into early next week. There is uncertainty on additional rainfall amounts with the GFS and ECMWF a bit different for their respective rainfall footprint. Leaning toward a wetter scenario than what the GFS is suggesting. We could see some additional rains of about 1-2 inches but more localized than widespread. Despite this, we could see some localized flooding after Helene is done over the area. Temperatures will trend down initially and are expected to hover in the 80s for high temperatures due to prevailing cloudiness and waves of rainfall. && .AVIATION... (18Z TAFS) Issued at 100 PM EDT Tue Sep 24 2024 VFR conditions expected through this TAF period. Tropical Storm Helene will cause conditions to deteriorate beginning Wednesday evening. && .MARINE... Issued at 310 PM EDT Tue Sep 24 2024 A weak pressure pattern and light onshore flow continues today. Small Craft Advisory conditions expected to develop during the evening hours on Wednesday with the approach of Potential Tropical Cyclone Nine in the gulf on Wednesday morning, winds will continue to strengthen with tropical storm conditions possible by early Thursday and continue into Friday morning. Some gradual improvement on Friday as the system pulls away to the north. A trough may linger over the region Friday night into the weekend with winds and seas below small craft advisory levels. Rip Currents: Moderate rip current risk today, high risk beginning tomorrow for NE FL and SE GA beaches. && .HYDROLOGY... Issued at 310 PM EDT Tue Sep 24 2024 The Flood Watch has been expanded to include all of southeast Georgia and northeast Florida. Excessive rainfall due to a Tropical Storm Helene will likely result in scattered areas of flash flooding and isolated episodes of considerable flash flooding, specifically in urban flood prone locations and areas that received a lot of rainfall this month. Widespread 3-6" of rain is forecast, with locally higher amounts. Strong southeasterly flow in response to the tropical system may bring tidal levels back into Minor or low-end Moderate flood at times of high tide along the Atlantic coast by Thursday evening. Given the current elevated tides already ongoing in the St Johns River, the potential for Moderate Flooding and impacts are possible during at least Thursday and Friday high tides. && .PRELIMINARY POINT TEMPS/POPS... AMG 70 88 72 81 / 0 20 50 90 SSI 77 85 76 83 / 0 10 50 80 JAX 74 88 76 85 / 0 30 60 90 SGJ 76 88 76 86 / 0 30 70 90 GNV 72 89 74 83 / 0 40 70 100 OCF 73 90 76 85 / 0 50 70 90 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Hurricane Watch for FLZ021-035-220-236-340-522. Flood Watch from Wednesday evening through Friday morning for FLZ021-023-024-030-031-033-035-038-120-124-125-132-133- 136>138-140-220-225-232-236-237-240-322-325-340-422-425-522. Coastal Flood Advisory until 5 PM EDT Wednesday for FLZ033-038- 125-132-137-225-325. Tropical Storm Watch for FLZ140-240. GA...Flood Watch from Wednesday evening through Friday morning for GAZ132>136-149-151>154-162-163-165-166-250-264-350-364. AM...None. && $$