941 FXUS62 KJAX 120142 AFDJAXArea Forecast Discussion National Weather Service Jacksonville FL 942 PM EDT Thu Sep 11 2025
...NORTHEASTERLY WINDS STRENGTHEN AT COASTAL LOCATIONS ON FRI... ...HAZARDOUS MARINE & BEACH CONDITIONS CONTINUE INTO NEXT WEEK... ...LOCALLY HEAVY DOWNPOURS POSSIBLE THIS WEEKEND ALONG THE NORTHEAST FL COAST...
For the latest NE FL and SE GA Daily Key Messages please visit: https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
.UPDATE... Issued at 943 PM EDT Thu Sep 11 2025
Late evening surface analysis depicts strong high pressure (1029 millibars) over Quebec, with this feature driving a cold front southward across New England and the eastern Great Lakes. Closer to our region, a stalled frontal boundary remains situated across southern FL, with weaker high pressure (1020 millibars) sprawling across the Ohio, Tennessee, and lower Mississippi Valleys. Aloft...a potent shortwave trough was digging southward across the Ohio Valley, with weaker shortwave energy crossing the southern Appalachians. Meanwhile, ridging was located over Texas and the southern Plains states. Latest GOES-East derived Total Precipitable Water imagery indicates that an unseasonably dry air mass remains in place across most of our area, with PWAT values generally between 1 - 1.25 inches for locations along and north of the I-10 corridor. Slightly higher moisture values were located across north central and portions of coastal northeast FL, where values were between 1.25 - 1.75 inches. Deep southwesterly flow prevails above 500 millibars (around 20,000 feet) per the evening sounding at Jacksonville at the base of a longwave trough that covers the eastern third of the nation, with this flow advecting a veil of mostly thin cirrus across our region, with some pockets of mid-level cloud cover across inland southeast GA and the northern Suwannee Valley. Otherwise, marine stratocumulus that was streaming onshore along the Atlantic coastal counties has shifted south of St. Augustine. Temperatures at 01Z were mostly in the 70-75 range. Dewpoints ranged from the 60s inland to around 70 at coastal locations.
Mostly thin cirrus cloud cover is expected to persist across most of our region overnight. Meanwhile, sharpening coastal troughing should result in increasing coverage of marine stratocumulus for coastal locations south of St. Augustine overnight, and few light showers could approach the Flagler County coast towards sunrise. A light breeze will persist at coastal locations, keeping lows mostly in the lower 70s. Decoupling winds inland will allow lows to fall into the 60s.
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.SHORT TERM... (Friday through Saturday night) Issued at 110 PM EDT Thu Sep 11 2025
An elongated upper trough will dig south across the eastern seaboard Friday into Saturday as potent shortwave energy rounds the base of the trough and across the area on Saturday. At the surface, high pressure centered over New England extends down the eastern seaboard maintaining breezy NNE winds and tightening the local coastal trough. Rounds of coastal showers will shift onshore in the NE flow mainly for areas south of Jacksonville and into north-central FL with isolated thunderstorm development during afternoon peak heating. Low level ridging will bring in drier air into inland SE GA as afternoon dewpoints fall into the mid/upper 50s in sharp contrast to dewpoints near 70 along the NE FL coast. Temperatures will be around or just below seasonable with highs in the low 80s along the coast to the mid-upper 80s inland. A gradient of low temps will range from low-mid 60s over inland SE GA/Suwannee river valley to the low 70s at the coast.
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.LONG TERM... (Sunday through next Thursday) Issued at 110 PM EDT Thu Sep 11 2025
The base of the upper trough becomes a closed upper low along the SE US coast Sunday into Monday and then develops a surface low off the Carolinas coast Monday into Tuesday. Uncertainty remains on the path this low will take whether it lingers off the Carolina coasts or lifts north up the eastern seaboard through mid-week. NNE flow continues with the area between high pressure over eastern US and the developing low off the SE US coast. The pattern of coastal showers shifting onshore to the NE FL coast and remaining relatively dry inland continues into early next week. A cold front approaches the area from the north toward mid-week. Highs will be in the low 80s at the coast and warm inland to the mid to upper 80s.
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.AVIATION... (00Z TAFS) Issued at 742 PM EDT Thu Sep 11 2025
VFR conditions are expected to prevail at the regional terminals through at least 13Z Friday. Brief periods of MVFR ceilings between 2,000 - 3,000 feet will be possible during the predawn and early morning hours on Friday at SGJ. MVFR ceilings will then prevail at SGJ after 14Z, where chances for showers gradually increasing through the afternoon hours. We maintained a PROB30 group at SGJ for MVFR ceilings during heavier showers that could potentially move over the terminal during the afternoon hours. A few showers could approach the CRG and JAX terminals on Friday afternoon, but confidence was too low to indicate anything other than vicinity shower coverage at this time. Marine stratocumulus cloud cover will otherwise increase at the northeast FL terminals on Friday, but ceilings are expected to remain VFR at this time. Light northeasterly surface winds this evening and overnight will shift to northerly at the regional terminals during the predawn and early morning hours. Surface winds will then shift to north- northeasterly by 13Z, with sustained speeds quickly increasing to 10-15 knots and gusty by the mid to late morning hours.
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.MARINE... Issued at 943 PM EDT Thu Sep 11 2025
High pressure building over eastern Canada tonight will shift southeastward towards New England on Friday, with this feature wedging down the southeastern seaboard by the afternoon hours. Meanwhile, a weak wave of low pressure will develop along a stalled frontal boundary over south Florida, with a coastal trough sharpening to the north of this feature over our local waters during the weekend. This weather pattern will create strengthening northeasterly winds on Friday, with Caution level speeds of 15-20 knots developing by the late morning hours and Small Craft Advisory conditions likely by the late afternoon or early evening hours. Seas of 3-4 feet both near shore and offshore tonight will build to 4-6 feet by Friday afternoon, with seas peaking in the 5-7 foot range this weekend. Showers and a few embedded thunderstorms will also increase across our local waters this weekend. Weak low pressure may lift northward across the Gulf Stream waters early next week, keeping breezy northeasterly winds, elevated seas, and chances for showers and thunderstorms in place for our area.
Rip Currents / Beach Erosion: Strengthening onshore winds will build breaker heights to 3-5 feet at the northeast FL beaches by Friday afternoon, with 2-4 foot breakers expected at the southeast GA beaches. A high rip current risk will continue at the northeast FL beaches on Friday, with a higher end moderate risk currently anticipated at the southeast GA beaches. These breakers will build during the weekend and early next week, potentially approaching 6 feet at the northeast FL beaches and around 4 feet at the southeast GA beaches. Building and increasingly rough surf conditions will result in a high rip current risk at all area beaches this weekend and early next week. Minor beach erosion can be expected around times of high tide, with moderate beach erosion possible at the northeast FL beaches.
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.HYDROLOGY... Issued at 943 PM EDT Thu Sep 11 2025
Trapped tides within the St. Johns River basin and its tributaries will persist during the next several days, resulting in minor flooding around times of high tide. Nuisance-type flooding of docks, boat ramps, over-topping of some sea walls/bulkheads, and flooding of low-lying roads can be expected. Water levels will generally run between 1 - 1.5 feet above Mean Higher High Water (MHHW) around times of high tide through Saturday, with strong onshore winds this weekend potentially raising levels to 1.5 - 2 feet above MHHW by Sunday and Monday.
Water levels along the Atlantic coast and the Intracoastal Waterway (ICCW) will gradually increase beginning on Friday, with minor coastal flooding possible during the weekend, as water levels generally rise to 1.5 - 2 feet above MHHW around times of high tide. This will mostly create nuisance type of flooding in normally flood prone locations.
We have thus extended the Coastal Flood Advisory along the Atlantic coast and ICCW, as well as within the St. Johns River and its tributaries, through early Saturday morning, with additional extensions expected this weekend and into early next week.
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.PRELIMINARY POINT TEMPS/POPS... AMG 62 88 63 86 / 0 0 0 0 SSI 71 83 71 82 / 0 10 20 20 JAX 69 85 71 84 / 0 10 10 40 SGJ 73 85 73 83 / 10 30 30 60 GNV 67 89 68 87 / 0 10 0 20 OCF 69 88 70 86 / 0 20 0 30
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.JAX WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk through late Friday night for FLZ124-125- 138-233-333.
Coastal Flood Advisory until 6 AM EDT Saturday for FLZ125-132- 137-138-225-233-325-333-633.
GA...None. AM...None. &&
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NWS JAX Office Area Forecast Discussion