Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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386 FXUS62 KJAX 161841 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 241 PM EDT Mon Sep 16 2024 ...New NEAR TERM, SHORT TERM, LONG TERM, MARINE, HYDROLOGY... .NEAR TERM... (Through Tonight) Issued at 227 PM EDT Mon Sep 16 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 This afternoon...While drier air aloft and at the surface slowly seeps southward into SE GA, there still will be a few isolated showers from the I-10 corridor northward into Coastal SE GA, while diurnal heating into the mid/upper 80s across NE FL and lingering deep moisture will still allow for scattered showers and isolated storms to develop across NE FL, mainly along and south of a line from Gainesville to St. Augustine, with the best chances of an isolated storm with heavy downpours across Marion/Putnam/Flagler counties into the early evening hours. Tonight...After a few early evening showers/isolated storms across Flagler/Putnam/Marion counties, expect a general decrease in cloudiness as a slightly drier West to Northwest steering flow on the SW side of PTC Eight brings mostly clear skies to most of SE GA with some lingering high clouds across most of NE FL through the night. This overall slight pattern shift will lead to the first rain-free overnight forecast along with some of the coolest temps so far this month with lower/middle 60s across inland SE GA, middle/upper 60s over most of inland NE FL and lower 70s along the Atlantic Coastal areas. Winds becoming Northwest and weakening to less than 5 mph over inland areas by the overnight hours will likely allow for some patchy fog formation towards sunrise. && .SHORT TERM... (Tuesday through Wednesday night) Issued at 227 PM EDT Mon Sep 16 2024 This period will be mainly dominated by the presence of a stacked upper low just north of the region and associated trough, mostly associated with the remnants of Potential Tropical Cyclone Eight. Flow will be generally west to southwest around the base of the trough, which will also keep the sea breeze pinned to the coast. With the diffuse frontal boundary pushed generally south of the area and some drier air aloft advected into the area at times, chances for convection will be toned down across most of the area, especially on Tuesday. Chances for convection will become more diurnal and daytime heating influenced compared to the recent stubborn pattern. Best chances for isolated to widely scattered showers/t`storms during the period will be south of I-10 and near the coastline where the pinned sea breeze develops. This regime will also allow temps to rise closer to if not slightly above average, with mid to upper 80s Tuesday and upper 80s to near 90 more common by Wednesday. && .LONG TERM... (Thursday through next Monday) Issued at 227 PM EDT Mon Sep 16 2024 The upper troughing pattern will not change significantly for at least the start of the long term period, as the parent upper low lifts northeastward and troughing across the area elongates. This should keep a pretty similar pattern for Thursday into Friday, with the main difference being a gradual veering of flow towards the northwest to possibly even northward. This type of flow regime would generally favor lower than normal shower/t`storm chances, and likely confined closer to the coasts and the influence of the sea breeze. Guidance starts to diverge towards the upcoming weekend, though the general consensus looks to be for the aforementioned upper low to start to dive back southward along the eastern seaboard and/or western north Atlantic. This will return a breezy northeasterly pattern to the area as surface ridging builds into the southeastern states in response. The extent of our rain potential will highly depend on the proximity the upper low gets to our region and/or how far south the associated digs, though for now looking like more eastern areas and especially the coasts have the highest chances, especially with the potential for development of a coastal trough with the proximity of the upper low. Temperatures start near to slightly above average for the end of the work week, then trend downward towards near to below average for the weekend. && .AVIATION... (18Z TAFS) Issued at 135 PM EDT Mon Sep 16 2024 Last gasp of MVFR CIGS at local TAF sites will slowly erode or lift with diurnal heating this afternoon, with all sites becoming MVFR by sunset with GNV/SGJ the last of the locations to become VFR this evening. Rainfall chances are on the low side so have only included VCSH at GNV/SGJ with this package until 00Z. Some clearing of skies and cooling of the boundary layer tonight along with near calm winds developing will lead to patchy fog formation and low stratus development at inland TAF sites with LIFR CIGS expected at GNV/VQQ in the 09-13Z time frame, while probs not as high at the coastal TAF sites, so have only added some MVFR conds at JAX and left SGJ/SSI/CRG at VFR levels. During diurnal heating Tuesday morning some redevelopment of MVFR CIGS is possible but for now have left as SCT020 for now in the 13-18Z time frame but TEMPO MVFR CIGS in the 1500-2500 ft range may need to be added in later TAF packages. && .MARINE... Issued at 227 PM EDT Mon Sep 16 2024 Small Craft Advisory conditions in the gusty North-Northeast flow at 15-20 knots this afternoon will shift to the Northwest tonight and slowly diminish as PTC Eight tracks further inland over the Carolinas which will slowly bring an end to Small Craft Advisory headlines as winds drop below 20 knots this evening and seas slowly fall being 7 feet later tonight or Tuesday morning. In the wake of PTC Eight lifting NW into the Carolinas a weak pressure pattern will remain in place through the mid-week time frame with light Southwest flow and diurnal sea breeze pattern over the near shore waters. Late in the week a frontal passage is expected on Thursday, then high pressure building into the Carolinas Friday and Saturday, which will lead to the next increase in Northeast flow likely close to Small Craft Advisory levels in the upcoming weekend time frame. Rip Currents: High risk of rip currents and rough surf of 4-6 ft today will likely become Moderate to marginally High on Tuesday as offshore flow sets up, but lingering swells will keep surf/breakers in the 3-5 ft range. && .HYDROLOGY... Issued at 227 PM EDT Mon Sep 16 2024 The St. Johns River Basin from Jacksonville southward through Putnam County has started to reach Moderate Flood levels during the latest high tide cycle, so have upgraded the Coastal Flood Advisory to a Coastal Flood Warning with the upcoming full moon over the next couple of days along with all of the runoff from all of the recent heavy rainfall. Peak tidal levels will generally be in the 2.0 to 2.5 ft above MHHW along the St. Johns River Basin. Along the SE GA/NE FL beachfront locations, similar peak tidal levels in the 2.0 to 2.5 ft above MHHW are expected early this week, which should remain in the Minor Flood categories, so have continued the Coastal Flood Advisory in these areas, although the current rough surf/breakers of 4-6 ft today will likely continue minor beach erosion during times of high tide at local beaches as well. && .PRELIMINARY POINT TEMPS/POPS... AMG 62 84 67 87 / 10 10 10 20 SSI 68 84 73 86 / 10 10 10 30 JAX 67 87 71 89 / 10 20 20 50 SGJ 71 87 73 89 / 10 20 20 40 GNV 68 88 70 89 / 10 30 10 50 OCF 70 90 71 91 / 20 30 0 40 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Warning until 5 AM EDT Wednesday for FLZ033-038- 125-132-137-225-325. Coastal Flood Advisory until 5 AM EDT Wednesday for FLZ124-133- 138. High Rip Current Risk through late tonight for FLZ124-125-133- 138. GA...Coastal Flood Advisory until 5 AM EDT Wednesday for GAZ154-166. High Rip Current Risk through late tonight for GAZ154-166. AM...Small Craft Advisory until 6 PM EDT this evening for AMZ450. Small Craft Advisory until midnight EDT tonight for AMZ452-454. Small Craft Advisory until 6 AM EDT Tuesday for AMZ470-472-474. && $$