Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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740 FXUS62 KJAX 251149 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 749 AM EDT Wed Sep 25 2024 ...New AVIATION... .NEAR TERM... Issued at 432 AM EDT Wed Sep 25 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 Calm and clear skies will continue through the overnight hours. By the morning hours, southeast winds will begin to see an uptick as the pressure gradient over the area begins to tighten as high pressure settles over the western Atlantic and Helene begins to move into the Gulf of Mexico. Winds for inland location will range from 10 to 15 mph with gusts up to 25 mph possible, while coastal locations will have winds from 15 to 25 mph and gusts up to 30 mph. Showers and thunderstorms during the afternoon to evening hours as outer rain bands of Helene begin to filter into the area. The highest rainfall amounts will be found over NE FL as some locations can get near 1" during the afternoon, with overnight amounts nearing the 1"-2" range. With the outer bands rotating into the area, there will be some potential for tornados, particularly along the coast, but instability will remain on the weaker side. During the overnight hours, precipitation chances will increase further as more rain bands continue to arrive to the area. Some rotation again will be possible within showers and storms, again coastal locations will be the spot to keep an eye on for any tornados that develop, but the overall instability will still be rather on the weak side. && .SHORT TERM... (Thursday through Friday night) Issued at 432 AM EDT Wed Sep 25 2024 This will be the most impactful period of weather as Tropical Storm Helene makes landfall along the Florida Panhandle or Big Bend region of northeast as possibly a Major Hurricane around sunset Thursday. Bands spiraling from the broad (soon to be) Hurricane will continue to push in from south to north across the area bring period of heavy rain and possibly scattered thunderstorms. Significant rainfall may lead to periods of flooding, some of which could become considerable along the Suwannee Valley region in particular through Thursday night. In addition to tropical storm conditions and potential hurricane conditions along the I-75 corridor and into Suwannee Valley, there will also be an Enhanced Convective risk through Thursday, mainly north of I-10, where scattered tornadoes may occur within the outer bands (squalls). More isolated tornado occurrences are possible elsewhere; the tornado threat will carry through all of Thursday into the nighttime hours as well. Helene will race northward after making landfall where it will be consumed by the large cutoff low to the northwest. Conditions will quickly improve Friday as the system pulls farther away. There is uncertainty in where the trailing frontal zone will stall out. Right now it appears that trailing boundary will stall to the south, which will usher in a dry slot across the region Friday. Jumping to the post-event (recovery) period, temperatures will be fairly warm in the upper 80s to around 90. && .LONG TERM... (Saturday through Tuesday) Issued at 432 AM EDT Wed Sep 25 2024 Helene will fully merge with the aforementioned upper low over the Mississippi River Valley area Friday Night, with a dry slot across most of the area and a lingering frontal boundary just to our south. The upper low moves very little through the weekend while becoming more broad and elongated. Meanwhile, surface high pressure sits near or just northeast of the northern Bahamas. This setup will allow a mostly southwesterly flow across the area. After a pretty short wrap around dry slot southwest of departing Helene on Friday and Friday Night, layer moisture looks to start to increase with the southwest flow along the nearly stationary boundary for the weekend. Guidance currently varies regarding the position of the boundary and therefore how much drier air remains entrained over the area aloft for the weekend. Regardless, looks as though highest rain chances will be over southern areas. Given the recent wet pattern and Helene passage, leaning towards a wetter solution for now and therefore included chances for most of the CWA. The elongated trough at mid levels looks to make some progress southeastward into the beginning of next week, which could continue a push of drier air aloft into the region, as well as southerly push of the aforementioned boundary to the south of the area with the development of a more west to northwest flow. The ECMWF suggests a wetter solution compared to the GFS similar to the weekend with a more limited southward push of the mid level trough and surface boundary, though both suggest generally lower POPs to start next week as compared to the weekend. Primarily southwest flow for the weekend should keep the area near to above average temperature wise, followed by closer to normal for Monday and Tuesday. && .AVIATION... (12Z TAFS) Issued at 735 AM EDT Wed Sep 25 2024 Winds will begin to build from out of the southeast by around 14-15z with sustained winds rising to be about 10-15 knots and gusts reaching upwards of 20-25 knots by around 18-19z. Increased chances for rainfall and possible thunderstorms this afternoon with more numerous developments forming ahead of the outer bands of Helene moving northward from out of the gulf overnight and into Thursday morning. && .MARINE... Issued at 432 AM EDT Wed Sep 25 2024 Tropical Storm Helene heads into the gulf this morning. Southeasterly winds will gradually strengthen through the day reaching tropical storm strength by Thursday morning, lingering at these levels into Friday. The tropical system will begin to move away from the area sometime on Friday. With a trough lingering over the area into the weekend, conditions are not expected to be at small craft advisory levels. Rip Currents: High risk of rip currents on for all area beaches through Friday as southeasterly flow increases ahead Tropical Storm Helene over the Gulf of Mexico. && .HYDROLOGY... Issued at 432 AM EDT Wed Sep 25 2024 A Flood Watch for all of southeast Georgia and northeast Florida is in effect. Excessive rainfall due to Tropical Storm Helene will likely result in scattered areas of flash flooding and isolated episodes of considerable flash flooding, particularly 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 88 72 81 72 / 30 80 100 80 SSI 86 75 84 77 / 10 80 90 80 JAX 88 75 86 76 / 30 80 90 80 SGJ 88 76 87 77 / 40 80 90 80 GNV 89 74 84 75 / 60 80 100 70 OCF 91 75 86 77 / 60 80 90 70 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Tropical Storm Warning for FLZ023-024-030-031-033-038-124-125- 132-133-136>138-140-225-232-237-240-325-425. Hurricane Warning for FLZ021-035-120-220-236-322-340-422-522. Flood Watch from this 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 8 AM EDT Friday for FLZ033-038-125- 132-137-225-325. High Rip Current Risk through Friday evening for FLZ124-125-133- 138. GA...Hurricane Warning for GAZ162-163. Flood Watch from this evening through Friday morning for GAZ132>136-149-151>154-162-163-165-166-250-264-350-364. High Rip Current Risk through Friday evening for GAZ154-166. Tropical Storm Watch for GAZ132>136-149-151>154-165-166-250-264- 350-364. AM...Tropical Storm Warning for AMZ450-452-454-470-472-474. && $$