Fernandina Beach to St. Augustine, FL Out 20 NM Marine Forecast
| Today...Southeast Winds 10 To 15 Knots, Becoming South Late. Seas 3 To 5 Feet, Occasionally To 6 Feet. Wave Detail: East 4 Feet At 6 Seconds And East 4 Feet At 10 Seconds. Intracoastal Waters A Light Chop. A Chance Of Showers With A Slight Chance Of Thunderstorms, Mainly During The Afternoon. |
| Tonight...South Winds Around 15 Knots, Becoming Southwest After Midnight. Seas 4 To 5 Feet, Occasionally To 6 Feet. Wave Detail: Southeast 5 Feet At 7 Seconds And Southwest 2 Feet At 5 Seconds. Intracoastal Waters A Moderate Chop. A Chance Of Showers With A Slight Chance Of Thunderstorms. |
| Friday...West Winds 10 To 15 Knots, Becoming Northwest Around 10 Knots During The Afternoon. Seas 3 To 5 Feet, Occasionally To 6 Feet. Wave Detail: Southeast 5 Feet At 8 Seconds And West 2 Feet At 4 Seconds. Intracoastal Waters A Light Chop. |
| Friday Night...North Winds Around 15 Knots, Becoming North Northeast 10 To 15 Knots After Midnight. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 4 Feet At 9 Seconds And North 3 Feet At 4 Seconds. Intracoastal Waters A Moderate Chop. |
| Saturday...Northeast Winds 5 To 10 Knots. Seas 3 To 4 Feet, Occasionally To 5 Feet. Wave Detail: East 3 Feet At 9 Seconds And North 2 Feet At 4 Seconds. Intracoastal Waters Mostly Smooth. |
| Saturday Night...Northeast Winds Around 5 Knots, Becoming Northwest 5 To 10 Knots After Midnight. Seas 2 To 3 Feet. Wave Detail: East 3 Feet At 9 Seconds. Intracoastal Waters Mostly Smooth. |
| Sunday...Northwest Winds 5 To 10 Knots, Becoming North Around 10 Knots During The Afternoon. Seas 2 To 3 Feet. Intracoastal Waters Becoming A Light Chop. |
| Sunday Night...Northeast Winds 10 To 15 Knots, Increasing 20 To 25 Knots After Midnight. Seas 3 To 4 Feet, Occasionally To 5 Feet, Building To 4 To 6 Feet, Occasionally To 8 Feet After Midnight. Intracoastal Waters Becoming Rough. |
| Monday...Northeast Winds 20 To 25 Knots, Becoming East Northeast During The Afternoon. Seas 6 To 8 Feet, Occasionally To 10 Feet. Intracoastal Waters Rough. Winds And Waves Higher In And Near Thunderstorms. |
| Area Forecast Discussion National Weather Service Jacksonville FL 609am EST Thu Dec 18 2025 .KEY MESSAGES... For the latest NE FL and SE GA Daily Key Messages please visit: https:/www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf - Isolated Thunderstorms Possible this Afternoon and Evening, Mainly Across the Suwannee Valley and Southeast GA. Locally Heavy Downpours are Possible. - Small Craft Advisory Offshore Tonight and Friday Morning. - Widespread Frost Likely and a Light Freeze Possible for Inland Southeast GA Early on Saturday Morning. - Moderate Rip Current Risk Continues at Area Beaches. High Risk Possible Early Next Week. - Small Craft Advisory Conditions Expected Early Next Week as Northeasterly Winds Increase at Coastal Locations. Near Term - Through Tonight Early morning surface analysis depicts coastal troughing situated over the northeast FL and southeast GA waters that was generating widely scattered showers, with isolated light showers or sprinkles traversing portions of the Interstate 95 corridor in our area. Meanwhile, strong low pressure (983 millibars) moving eastward from North Dakota towards northern Minnesota was pushing a cold front southeastward through the Plains states and the southern Rockies. Aloft...a shortwave trough embedded within the southern branch of the jet stream was progressing eastward across southwestern Louisiana and western of the Gulf, with deepening southwesterly flow downstream of this feature across our region. Otherwise, a potent shortwave trough traversing the northern branch of the jet stream was digging southeastward from the Dakotas towards the Plains states and the Upper Midwest. Latest GOES-East derived Total Precipitable Water imagery indicates that moisture levels were gradually increasing across our area as southwesterly flow deepens, with values generally just below 1 inch at inland locations and just above 1 inch along the I-95 corridor, or closer to the coastal trough. Multi-layered cloud cover remains thicker for locations north of the I-10 corridor, with breaks in the cloud cover allowing for patchy fog to develop across northeast and north central FL. Temperatures and dewpoints at 09Z were generally in the 50s, except around 60 at coastal locations. Northern stream troughing digging southeastward from the Plains States and the Upper Midwest will pivot eastward across the Great Lakes, Ohio, Tennessee, and lower Mississippi Valleys tonight. This digging trough will lift the shortwave trough traversing the northern Gulf coast northeastward through the Deep South this evening, with this shortwave then filling as it becomes absorbed by the northern stream trough on Friday. A 100-knot jet streak at 250 millibars (around 25,000 feet) downstream of the digging northern stream trough will traverse the southeastern states today and will strengthen to around 120 knots as it reaches the Carolina coast by sunrise on Friday. Diffluent flow associated with this jet streak will result in increasing convective coverage near the Gulf's loop current south of the FL panhandle this morning, with showers emanating from this convection overspreading the Suwannee Valley and southeast GA this afternoon as strengthening southwesterly flow advects a plume of deeper moisture, featuring PWATs (Precipitable Waters) of 1.5 - 1.75 inches from the eastern Gulf across our area. Coastal troughing over our local Atlantic waters will continue to lift northward this morning ahead of the approaching southern stream trough, bringing a few light showers or sprinkles to the I-95 corridor. Breaks in the multi-layered cloud cover could develop patchy to areas of fog during the predawn and early morning hours, mainly across northeast and north central FL. Low level winds will veer from easterly to southeasterly this morning and then southerly by late afternoon, with less forcing for shower activity expected for locations east of the I-75 corridor this afternoon. Despite thickening cloud cover, warm air advection and less shower coverage will allow highs east of the I-75 corridor to climb to the mid to upper 70s, with lower 70s expected for much of inland southeast GA, despite increasing shower coverage this afternoon. Southeasterly surface winds over cool shelf waters may keep highs in the upper 60s for coastal southeast GA, while winds turning more southerly this afternoon allow highs to reach the 70-75 range for coastal northeast FL. As the southern stream shortwave trough moves across AL and GA tonight, a low level jet of 40-50 knots at 850 millibars (around 5,000 feet) will traverse the Suwannee Valley and southeast GA late this afternoon and early this evening could help to generate a few embedded, mostly elevated thunderstorms that could persist through around midnight tonight. With little to no surface-based CAPE available, we do not expect convection to become strong, but any embedded thunderstorms that manage to develop over the Suwannee Valley and southeast GA could produce briefly heavy downpours and sporadic lightning strikes. Rainfall amounts in the Suwannee Valley and southeast GA will generally run in the one-quarter to one-half inch range, with localized totals up to one inch possible. Locations south of I-10 in northeast and north central FL will likely only end up in the one-tenth to one-quarter of an inch range, as coverage remains scattered at best through tonight. Deeper moisture will quickly shift offshore after midnight tonight, leaving behind low stratus clouds as a dry slot moves overhead in advance of an approaching weak cold front. This front may cross the Altamaha/Ocmulgee/Alapaha Rivers during the predawn hours on Friday, with scattered low-topped showers developing ahead of the approaching front across the Suwannee Valley and inland southeast GA before sunrise. Lows will possibly fall to the mid and upper 50s around or just after sunrise on Friday for inland southeast GA, with low and mid 60s prevailing elsewhere as southwest winds remain sustained at 10-15 mph overnight. Short Term - Friday Through Saturday Night A cold front will push through the area on Friday, with dry and cool air filtering into the area behind the front. High pressure builds in behind the front, pushing off towards the Atlantic by the back half of the upcoming weekend. Northwesterly winds behind the cold front will bring in cooler and drier air into the area, particularly over inland SE GA where daytime highs will dip into the mid to upper 60s. While NE FL will feel daytime highs in the mid to upper 70s. With the dry air filtering into the area, cloudy skies will steadily become clear by the afternoon to evening hours. Clearer skies and near calm winds over SE GA during the overnight hours, will again bring the potential for a light freeze and patchy frost to develop during the predawn hours as overnight lows will dip into the mid 30s. Overnight lows over NE FL will dip to the upper 30s to mid 40s for inland locations, while coastal locations will be in the 40s with the most southern coastal locations in the lower 50s. High pressure settles over the area on Saturday, with light and easterly to northeasterly winds present throughout the day. Similar pattern in temperatures as Friday with daytime highs in the mid to upper 60s across SE GA and 70s across NE FL. Slightly warmer overnight temperatures and some cloud cover will limit any frost development on Saturday Night. Overnight lows in the upper 30s over inland SE GA, 40s across inland NE FL, and upper 40s to lower 50s along the coast. Long Term - Sunday Through Wednesday High pressure will begin to weaken over the area as the next frontal boundary pushes through on Sunday, with high pressure once again building across the region on Monday. Current guidance indicate dry conditions will continue through the forecast period across inland locations, with scattered chances of showers primarily confined over the outer waters on Monday. Onshore flow develops at the start of the upcoming week, with elevated winds over the local waters on Monday as the high pressure shifts eastward. Temperatures are expected to remain close to or slightly above normal through the forecast period. Marine A weak trough over the northeast Florida waters this morning will lift northward as a warm front, moving north of the Georgia waters by early this afternoon. Scattered showers will develop over our local waters this morning, followed by increasing chances for showers and a few embedded thunderstorms well in advance of an approaching cold front late this afternoon and evening. Southeasterly winds will gradually strengthen this morning, with Caution conditions expected offshore. Southwesterly winds will then increase tonight, with Small Craft Advisory conditions developing offshore around sunset. Winds will then shift to westerly during the passage of a cold front on Friday morning, with northwest and then northerly winds developing following the frontal passage on Friday afternoon and night. High pressure will settle over our local waters during the weekend, allowing for winds and seas to diminish. A weakening frontal boundary will approach our region from the north on Monday as strong high pressure builds over the Mid-Atlantic states, with this feature wedging down the southeastern seaboard as another coastal trough develops over our local waters. This feature may develop showers over our local waters early next week. Small Craft Advisory conditions will likely develop after midnight on Sunday night as northeasterly winds surge, with elevated seas likely persisting through Tuesday as onshore winds only gradually subside. Rip Currents Southeast GA Moderate Today and Friday Northeast FL Moderate Today and Friday Fire Weather Chances of showers will steadily increase throughout the day, with higher chances over inland southeast Georgia, ahead of an approaching cold front from the northwest. Low dispersions expected once again across southeast Georgia, portions of the Suwannee Valley in northeast Florida, and along coastal locations. Southerly winds shift to become southwesterly by Friday morning, shifting to become northwesterly behind the cold front by Friday afternoon. Dry and cooler air filters into the area behind the front which will see min RHs values dip to the upper 30s on Friday and then the lower 30s over inland southeast Georgia on Saturday. High pressure builds over the region once again on Saturday, pushing away from the area on Sunday as lower dispersions will once again develop across southeast Georgia and coastal locations. FOG POTENTIAL AND OTHER REMARKS: Patchy to areas of locally dense fog is possible during the predawn to early morning hours across inland portions of northeast and north central Florida Today. A light freeze and patchy frost will be possible across inland portions of southeast Georgia during the predawn and early morning hours on Saturday. NOAA Jacksonville FL Office: Watches - Warnings - Advisories FL...None. GA...None. Marine Small Craft Advisory from 7pm this evening to 1pm EST Friday for AMZ470-472-474. |
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