Area Forecast Discussion
Issued by NWS Jacksonville, FL
Issued by NWS Jacksonville, FL
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753 FXUS62 KJAX 161741 AFDJAX Area Forecast Discussion National Weather Service Jacksonville FL 141 PM EDT Mon Sep 16 2024 ...New AVIATION... .UPDATE... Issued at 939 AM 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 Precipitable water values across northeast FL is between 1.85 to 1.95 inches with drier air indicated just north of the Altamaha around 1.65 inches. "Drier" air have started working into the northern part of the CWA with north-northeasterly surface winds across the area and will continue to do so today. Wrap around cloudiness will remain in place across the region as PTC - Potential Tropical Cyclone offshore of South Carolina moves to the northwest into South Carolina this afternoon as unorganized low. Limited precipitation potential this afternoon across the region with isolated to widely scattered showers south of Waycross. There will some convection closer to north central FL and Flagler counties this afternoon with some convergent feature noted in the models in addition to the higher moisture levels. Long period onshore flow and astronomical high tides will continue to promote poor to hazardous marine and beach conditions through tonight, then improving conditions Tuesday. && .SYNOPSIS... Issued at 448 AM EDT Mon Sep 16 2024 Early morning surface analysis depicts the center of Potential Tropical Cyclone (PTC) #8 drifting over the Gulf Stream Waters adjacent to the South Carolina coast. Meanwhile, strong high pressure (1028 millibars) remains anchored off coastal New England, with this feature wedging down the spine of the Appalachian mountains and into the Deep South. Otherwise, a stubborn, wavy and nearly stationary frontal boundary remains in place along the Interstate 4 corridor in central FL, with this boundary extending along the northern Gulf coast. Aloft...the "Rex Blocking" pattern continues over the eastern half of the nation, with stout ridging extending across the eastern Great Lakes, New England, and the Mid-Atlantic states. This feature was keeping the remnant trough that was once Francine drifting over the Ozarks and lower Mississippi Valley, with this trough axis extending southeastward along the northern Gulf coast. Low-topped showers and lower stratus clouds continue to advect southwestward from PTC #8 across our Atlantic waters, with this activity brushing the I-95 corridor. Multi-layered cloudiness prevails across our area, but thinner, mainly high altitude cloudiness was located over inland portions of southeast GA, where dewpoints were falling through the 60s as of 08Z and temperatures were generally around 70. Breezy northerly winds prevail at coastal locations, with temperatures and dewpoints in the 70s elsewhere. && .NEAR TERM... (Today and Tonight) Issued at 448 AM EDT Mon Sep 16 2024 PTC #8 should organize into a Tropical Storm (Helene) later this morning as it drifts northwestward towards the Carolina coast, with landfall expected by late afternoon. Wrap-around moisture on the southwestern periphery of this cyclone`s circulation will keep stubborn low and mid level cloudiness in place across most of coastal southeast GA, northeast and north central FL into the early afternoon hours, with a few low topped showers and/or drizzle occasionally impacting locations along the I-95 corridor this morning. Breaks in the multi-layered cloudiness should develop this afternoon across north central FL, where slightly deeper moisture, a destabilizing atmosphere, and the presence of the stubborn frontal boundary over central FL could develop showers and a few embedded thunderstorms by late afternoon as highs climb to the mid and upper 80s. Cloudiness will also thin out by the mid to late afternoon hours elsewhere, with low level winds backing to northwesterly, ushering in a drier air mass that will allow highs to climb to the low and mid 80s for most locations by late afternoon. This drier air mass should shut off showers rotating around the periphery of PTC #8 later this afternoon along the I-95 corridor. Any convection that manages to develop across north central FL late this afternoon should diminish by sunset this evening. PTC #8 will continue its slow northwestward motion across inland portions of South Carolina tonight, with a drier air mass overspreading our region overnight. Fair skies and diminishing winds will allow for radiational cooling for locations along and north of the I-10 corridor, allowing lows to fall below mid-September climatology, as values bottom out in the mid 60s for most of inland southeast GA by sunrise on Tuesday. Lows for inland northeast FL will fall to the upper 60s, with lower 70s closer to the lingering front in north central FL, and low to mid 70s for coastal locations. && .SHORT TERM... (Tuesday through Wednesday Issued at 448 AM EDT Mon Sep 16 2024 The area will be on the southern periphery of a weakening, stacked low associated with the remnants of PTC #8 over the Carolinas through mid-week. West-southwesterly flow will advect in drier air on the south side of the low limiting convection over much of SE GA. Convection will return to be diurnally driven and enhanced by the sea breezes. In the WSW flow, the Atlantic sea breeze will be pinned to the I-95 corridor. Isolated to scattered showers and storms will be possible each afternoon into evening mainly over NE FL. Temperatures warm to above climo with highs in the mid 80s to low 90s and lows in the upper 60s to low 70s. && .LONG TERM... (Thursday through Sunday) Issued at 448 AM EDT Mon Sep 16 2024 The upper low lifts northeastward into the mid-Atlantic region through Friday as surface high pressure builds down into the SE from the Great Lakes region. NNW flow aloft develops which will maintain drier conditions across the area. Isolated to widely scattered showers and storms will be possible with the best chances in the NE FL. The upper low dives south down the eastern seaboard for the weekend as surface high pressure wedge extends down the eastern US. This will bring a return of breezy northeasterly winds for the weekend and potentially higher chances for rain. Above normal temps on Thursday and Friday return to below normal for the weekend with the potential increase of cloud cover and rain. && .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 448 AM EDT Mon Sep 16 2024 Potential Tropical Cyclone 8 will likely become a Tropical Storm later this morning before pushing northwestward towards coastal South Carolina this afternoon. Seas will peak this morning in the 7-9 foot range offshore and 6-8 feet near shore. Small Craft Advisory conditions will continue throughout our local waters this morning, with conditions improving over the near shore waters by this evening as winds shift to northwesterly and diminish. Seas should remain at Caution levels of 4-6 feet near shore tonight, with 5-7 foot seas prevailing offshore. Seas will then fall below Small Craft Advisory criteria offshore by early Tuesday morning, with Caution level seas prevailing through Tuesday afternoon. A leftover frontal boundary stretching across central Florida will slowly lift northward across the northeast Florida waters through midweek, possibly developing a few showers and thunderstorms during the late afternoon and early evening hours. Seas will diminish to the 2-4 foot range both near shore and offshore by midweek. Another surge of onshore winds will be possible towards the weekend as strong high pressure wedges down the southeastern seaboard. Rip Currents/High Surf: Breaker heights will peak around 6 feet this morning at the northeast FL beaches and 4-5 feet at the southeast GA beaches. Surf heights will begin to gradually diminish this afternoon as winds shift to northwesterly, but a high risk of rip currents will continue at all area beaches today. Breaker heights will remain elevated in the 3-5 foot range on Tuesday at the northeast FL beaches and 2-3 feet at the southeast GA beaches, with a lingering northeasterly swell likely creating a higher end moderate risk at area beaches. && .PRELIMINARY POINT TEMPS/POPS... AMG 83 64 85 68 / 20 0 20 10 SSI 83 74 83 73 / 20 0 10 10 JAX 84 68 87 72 / 20 10 30 20 SGJ 84 74 87 74 / 30 10 30 20 GNV 85 68 89 71 / 20 0 30 10 OCF 87 70 90 72 / 30 10 30 10 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 5 AM EDT Wednesday for FLZ033-038- 132-137-325. Coastal Flood Advisory until 5 AM EDT Tuesday for FLZ124-125-133- 138. High Rip Current Risk through late tonight for FLZ124-125-133- 138. GA...Coastal Flood Advisory until 5 AM EDT Tuesday for GAZ154-166. High Rip Current Risk through late tonight for GAZ154-166. AM...Small Craft Advisory until 5 PM EDT this afternoon for AMZ450. Small Craft Advisory until 11 PM EDT this evening for AMZ452-454. Small Craft Advisory until 5 AM EDT Tuesday for AMZ470-472-474. && $$