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Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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520 FXUS62 KJAX 181735 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 135 PM EDT Thu Jul 18 2024 ...New AVIATION... .UPDATE... Issued at 840 AM EDT Thu Jul 18 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 A few tweaks to the forecast to lower max temps with lingering cloud cover and stormy SW flow brining once again an earlier start to convection today. Around 920 am, storms were already approaching the I-75 corridor from the Gulf Coast region. Max temps will top out in the upper 80s to near 90 across our western zones to the low 90s toward the east before convection. No major changes to the precipitation forecast with 60-75% rain chances expected across the area today. Convection will once again progress across NE FL through late afternoon, then develop across SE GA into the afternoon and early evening south of a surface front. The main difference for today`s storms compared to yesterday is there there may be a few stronger to isolated severe storms especially near and north of the I-10 corridor as vertical lift will be enhanced with an approaching mid level short wave trough, which was already enhancing storms across SW GA this morning. Also the 12z JAX RAOB showed slightly steeper mid level lapse rates with 500 mb temps cooling to near -8 degC compared to -6degC yesterday morning. Just a few knots of increased mid and upper level westerly wind shear as well today compared to yesterday. The main hazards in storms will continue to be gusty wet downbursts, with magnitude potential a little stronger today with gusts of 40-60 mph possible. Locally flooding rainfall will continue to be a concern, especially near the Altamaha River basin where rainfall amounts yesterday neared 4-5 inches in parts of Coffee, Jeff Davis and Appling counties. Rainfall will tapper off with loss of diurnal instability and in the wake of the departing short wave trough this evening, with dry conditions expected after midnight and mild, but muggy lows in the low to mid 70s. Some shallow ground fog and mist will be possible toward sunrise especially where recent heavy rainfall occurred. && .NEAR TERM... Issued at 254 AM EDT Thu Jul 18 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 Any lingering convection over interior southeast GA has fizzled over the past couple hours, with just some occasional leftover debris clouds and a seasonably mild night tonight. A cold front currently draped across the Ohio and Tennessee River Valley area will make some pretty quick progress southward through the rest of today ahead of its parent upper trough, both of which will quickly start to lose momentum and stall north of the area by tonight. This will push the surface ridge overhead a bit further south and east, but also strengthen the mostly uniform flow aloft slightly as well. The main "take home" with all of this will be a similar regime as seen over the past few days with a stacked southwest flow, earlier onset to convective timing, and a sea breeze pinned around the I-95 to the coast vicinity. The slightly stronger flow aloft will certainly keep the threat for some strong storms across the area, especially as convection from earlier in the day collides with the Atlantic sea breeze during the afternoon. Wet downbursts in the 40-55mph range will be the primary hazard, and an isolated severe storm also quite possible. Temperatures are also expected to be similar to those seen on Wednesday. The warmer southwesterly flow will be slightly offset by the earlier start to convection and overspreading cloud cover for many, resulting in highs forecast in the low to mid 90s. Though depending on timing and coverage, some areas could under or over achieve. Similar to Wednesday, some showers and t`storms may linger over interior southeast GA into the start of the overnight hours tonight closer to the frontal zone mentioned above. Otherwise, just some leftover clouds with lows in the mid to upper 70s. && .SHORT TERM... (Friday through Saturday night) Issued at 254 AM EDT Thu Jul 18 2024 Predominant southwesterly steering flow that has been locked in across the region through the majority of the week will shift and prevail out of the south through Saturday as ridging rebuilds to the east. Though there will be pockets off "drier" air (PWATs < 2"), for the most part abundant moisture will be available and fuel scattered convection along the sea breezes, with coverage blossoming inland as sea breezes merge. Due to outflow and and other mesoscale boundary interactions, it`s tough to discern where exactly the merger and stronger convection potential will be. That said, placing the potential for widespread showers and a few strong pulses roughly between the Highway 301 and I-95 corridors on Friday. As flow shifts a bit more southerly by Saturday, the merger should occur more inland, generally between Highway 301 and I-75. As has been the case with this moist airmass, concerns with convection will be localized to areas flooding, particularly in urban locations or where the grounds are still soaking in rain from the last couple of days. Frequent lightning and gusty outflow winds are also possible with deeper pulses, likely along the sea breeze collision zone. Before convective cooling occurs, temperatures will push into the low 90s each day with the highest heat index readings near the coast up to 105-108F. && .LONG TERM... (Sunday through Wednesday) Issued at 254 AM EDT Thu Jul 18 2024 The seasonably active thunderstorm period continues through Sunday with a more progressive Atlantic sea breeze amid southeasterly flow. Appears that an inverted shortwave or two will rotate around the western extent of the stacked Bermuda ridge next week; these features may serve to enhance storm chances further Monday and possibly Tuesday, though it will depend on how fast and where they track. Available moisture will retreat some toward the middle of next week, potentially in the wake region of the aforementioned shortwaves, and this may limit storm coverage during the middle part of next week. Temperatures will trend near to above normal with highs in the low-mid 90s and lows in the 70s. && .AVIATION... (18Z TAFS) Issued at 132 PM EDT Thu Jul 18 2024 TEMPO groups are included for all terminals over the next 3-4 hours due to TS with MVFR restrictions and wind gusts of 25 kts. As of 30-40 kts are possible today in stronger cells. Convection will press offshore of the local Atlantic coast and decrease in coverage from west to east through 22-01z. Lingering debris clouds overnight with dry conditions by 06z. Potential for MVFR due to shallow ground fog/mist after 07z 7/19 with a land breeze from the SW 2-4 kts at coastal terminals through 12z Friday. After daybreak, SW winds will increase with lingering debris clouds. Showers and isolated storms will approach GNV from the SW through 18z. && .MARINE... Issued at 254 AM EDT Thu Jul 18 2024 The axis of Atlantic ridging will continue to extend westward across the northeast Florida waters through Thursday, creating a prevailing southerly wind flow across our local waters. Winds will become onshore during the early afternoon hours on Thursday as the sea breeze develops and pushes inland. Showers and thunderstorms will approach from the west, possibly impacting the near shore waters by the mid to late afternoon hours on Thursday. A frontal boundary will then sink southward across the southeastern states on Friday, with this feature stalling well to the northwest of our local waters during the upcoming weekend. Showers and thunderstorms will likely increase in coverage throughout our local waters during the weekend and early next week before the axis of Atlantic ridging lifts northward, placing our local waters within a prevailing southeasterly wind flow towards the middle portion of next week. Rip Currents: Developing onshore winds during the early afternoon hours will combine with a persistent east southeasterly ocean swell to create a lower-end moderate risk at all area beaches through at least Friday. && .PRELIMINARY POINT TEMPS/POPS... AMG 74 95 73 93 / 40 70 40 60 SSI 79 93 79 91 / 40 50 40 60 JAX 75 95 76 94 / 30 70 30 70 SGJ 77 93 77 93 / 30 50 20 60 GNV 74 93 73 93 / 20 80 20 70 OCF 74 93 75 93 / 20 80 30 70 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...None. GA...None. AM...None. && $$