Marine Weather Net

Fernandina Beach to St. Augustine, FL Out 20 NM Marine Forecast


REST OF TONIGHT

S
WINDS
5 - 10
KNOTS

SATURDAY

SW
WINDS
5 KNOTS

SATURDAY NIGHT

S
WINDS
10 - 15
KNOTS

SUNDAY

W
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
AMZ452 Forecast Issued: 823 PM EDT Fri Jul 18 2025

Rest Of Tonight...South Winds 5 To 10 Knots. Seas 2 To 3 Feet. Wave Detail: Southeast 3 Feet At 8 Seconds. Intracoastal Waters Light Chop.
Saturday...Southwest Winds Around 5 Knots, Becoming Southeast In The Afternoon. Seas Around 2 Feet. Wave Detail: Southeast 2 Feet At 8 Seconds. Intracoastal Waters Light Chop.
Saturday Night...South Winds 10 To 15 Knots, Becoming Southwest 5 To 10 Knots After Midnight. Seas 2 To 3 Feet. Wave Detail: Southeast 3 Feet At 8 Seconds. Intracoastal Waters A Moderate Chop.
Sunday...West Winds 5 To 10 Knots, Becoming South In The Afternoon. Seas Around 2 Feet. Wave Detail: Southeast 2 Feet At 8 Seconds. Intracoastal Waters Light Chop.
Sunday Night...South Winds Around 10 Knots, Becoming West After Midnight. Seas 2 To 3 Feet. Wave Detail: Southeast 2 Feet At 4 Seconds And Southeast 2 Feet At 8 Seconds. Intracoastal Waters Light Chop. A Slight Chance Of Showers And Thunderstorms In The Evening.
Monday And Monday Night...West Winds 5 To 10 Knots. Seas Around 2 Feet. Wave Detail: South 2 Feet At 4 Seconds And Southeast 2 Feet At 8 Seconds. Intracoastal Waters Light Chop. A Chance Of Showers And Thunderstorms.
Tuesday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. Intracoastal Waters Light Chop. Showers And Thunderstorms Likely. Winds And Waves Higher In And Near Thunderstorms.
Wednesday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. Intracoastal Waters Light Chop. Showers And Thunderstorms Likely. Winds And Waves Higher In And Near Thunderstorms.
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Area Forecast Discussion
National Weather Service Jacksonville FL
716pm EDT Fri July 18 2025

Synopsis
Issued at 213pm EDT Fri July 18 2025

Noon surface analysis depicts high pressure (1024 millibars) positioned to the east of the Gulf Stream waters off the southeastern seaboard. Meanwhile, the remnant circulation of Invest 93L was meandering through the lower Mississippi Valley. Aloft...ridging centered from the southeastern seaboard southward through the Bahamas continues to gradually retrograde westward, with this feature steering a weak trough slowly northward across eastern portions of the Gulf and FL peninsula. Latest GOES-East derived Total Precipitable Water imagery indicates that deep tropical moisture remains in place across our area, with PWATs generally around or just above 2 inches, while lower values in the 1.6 - 1.8 inch range were advecting northward from the Interstate 4 corridor in central FL. Temperatures have soared to the 90-95 degree range at most inland locations as of 18Z, with dewpoints in the 70s yielding heat index values in the 100-108 degree range thus far this afternoon. While a healthy cumulus field was building across our region, convection thus far as remained to the west of the Suwannee and Alapaha Rivers, where initiation was being triggered by the inland moving Gulf coast sea breeze boundary.

Near Term
(through Tonight) Issued at 213pm EDT Fri July 18 2025

Although subsidence will be strengthening with the retrograding ridge approaching our region, some cooling aloft associated with weak troughing aloft approaching from the south and plenty of low level moisture should result in scattered late afternoon and evening convection developing along inland moving sea and river breeze boundaries, with a slightly higher coverage possible towards sunset along the U.S. Highway 301 corridor, where mesoscale boundaries are likely to collide. Southwesterly steering flow could bring some of this activity back towards the I-95 corridor after sunset before activity diminishes later this evening, or before midnight. A few storms will pulse as convective boundaries collide and may briefly become strong early this evening, with stronger storms being capable of producing downburst winds of 40-50 mph, frequent lightning strikes, and locally heavy downpours. Debris cloudiness from this evening's scattered convection will then gradually thin out overnight, with lows only falling to the mid 70s inland, ranging to around 80 at area beaches.

.SHORT TERM... (Saturday through Sunday) Issued at 213pm EDT Fri July 18 2025

This weekend, low/mid level ridging will shift from the Atlantic over southern portions of the area centered over central to north central FL and then shift westward into the NE Gulf waters. This will limit chances for T'storms to mainly under 30 percent over north central FL and under 20 percent over NE FL with silent pops under 10 percent over most of SE GA. Sky cover will be mostly sunny under the high and along with rising heigheights under the ridge will allow high temperatures to rise into the mid to upper 90s on Saturday and upper 90s to around 100 degrees inland. West to SW flow will will pin the Atlantic seabreeze to the immediate coast Saturday and offshore on Sunday allowing highs to reach the low to mid 90s even at the beachfront.

The main story will be the heat index values this weekend as the high temperatures also combine with dewpoints in the mid 70s to create heat index values 108-112 degrees across much of the area, except generally north and west of Waycross. Therefore, heat advisories are likely for a majority of NE FL and along the SE GA

Long Term
(Monday through Thursday) Issued at 213pm EDT Fri July 18 2025

Next week, the low/mid level ridge will slide westward into the north central Gulf as a trough/weak frontal boundary settles southward along the Southeast U.S. coast towards the area.

For Monday, scattered to numerous showers and T'storms will develop as moisture pools ahead of the trough/front with PWATs (Precipitable Waters) climbing to 2.0 - 2.25 inches (90th percentile this time of year). Winds will shift more easterly as the front approaches from the north with highest T'storm chances west of highway 301.

By Tuesday and Wednesday, the front will slide into the area with PWATs (Precipitable Waters) reaching near daily max values (above 2.3-2.4 inches). The combination of high moisture, lift from the front and shortwave energy aloft with a mid/upper trough moving SE off the eastern seaboard will promote widespread showers and T'storms over our area each day. While mid level temps will stay near to slightly warmer than climatology (about -5 to -7 Celsius), steep low level lapse rates and high moisture will allow for strong downburst winds to occur between seabreeze and storm outflow collisions along with locally heavy rainfall from heavy downpours and frequent lightning.

On Thursday, the front will begin to weaken with some drier air working in from the north into SE GA as weak high pressure extends from near coastal New England into the Carolinas. This will limit chances to scattered T'storms over SE GA and scattered to numerous T'storms across NE FL.

Temperatures will begin the period above normal as highs remain in the mid to upper 90s away from the coast with high heat index values potentially into heat advisory levels Monday before highs trend back

Long Term
(Monday through Thursday) Issued at 213pm EDT Fri July 18 2025

Next week, the low/mid level ridge will slide westward into the north central Gulf as a trough/weak frontal boundary settles southward along the Southeast U.S. coast towards the area.

For Monday, scattered to numerous showers and T'storms will develop as moisture pools ahead of the trough/front with PWATs (Precipitable Waters) climbing to 2.0 - 2.25 inches (90th percentile this time of year). Winds will shift more easterly as the front approaches from the north with highest T'storm chances west of highway 301.

By Tuesday and Wednesday, the front will slide into the area with PWATs (Precipitable Waters) reaching near daily max values (above 2.3-2.4 inches). The combination of high moisture, lift from the front and shortwave energy aloft with a mid/upper trough moving SE off the eastern seaboard will promote widespread showers and T'storms over our area each day. While mid level temps will stay near to slightly warmer than climatology (about -5 to -7 Celsius), steep low level lapse rates and high moisture will allow for strong downburst winds to occur between seabreeze and storm outflow collisions along with locally heavy rainfall from heavy downpours and frequent lightning.

On Thursday, the front will begin to weaken with some drier air working in from the north into SE GA as weak high pressure extends from near coastal New England into the Carolinas. This will limit chances to scattered T'storms over SE GA and scattered to numerous T'storms across NE FL.

Temperatures will begin the period above normal as highs remain in the mid to upper 90s away from the coast with high heat index values potentially into heat advisory levels Monday before highs trend back

Marine
Issued at 1229pm Fri July 18 2025

High pressure centered off the southeastern seaboard will shift slowly westward towards our local waters tonight and Saturday. Only isolated late afternoon and evening thunderstorms are possible across the near shore waters through Saturday. Troughing will then develop on Sunday over the southeastern states, with this feature potentially sharpening near our local waters early next week. Chances for showers and thunderstorms will increase beginning late Sunday afternoon, with strong to isolated severe afternoon and evening thunderstorms potentially impacting our local waters each day next week. Seas of 2 to 3 feet will prevail both near shore and offshore during the next several days.

Rip Currents
A persistent east-southeasterly ocean swell will combine with developing onshore winds this afternoon to create a lower end moderate risk at all area beaches. Similar conditions are expected on Saturday, with a low risk possible by Sunday and Monday due to low surf heights.

Fire Weather
Issued at 1229pm Fri July 18 2025

Southwesterly transport speeds around 10 mph this afternoon will combine with elevated mixing heigheights to create generally fair daytime dispersion values, except good values for locations north of Waycross in southeast GA and poor values at coastal locations, where onshore surface winds will develop by mid-afternoon. Surface and transport winds will become west-southwesterly on Saturday, with breezy transport speeds developing north of the I-10 corridor during the afternoon hours. These breezy conditions will combine with elevated mixing heigheights to create high daytime dispersion values across most of inland southeast GA, while good values prevail elsewhere for inland locations, except fair values for locations south of the I-10 corridor, where speeds will remain light. Surface and transport winds will then shift to westerly on Sunday, with breezy transport speeds combining with elevated mixing heigheights to create high daytime dispersion values for inland locations along and north of I-10, with good values forecast elsewhere. Afternoon and evening thunderstorm coverage will increase next week.

Climate
Issued at 1229pm Fri July 18 2025

Daily record high temperatures at our designated climate sites through Tuesday, July 22

Today Saturday Sunday Monday Tuesday --------------------------------------------------- Jacksonville 100/1887 101/2000 103/2000 102/1942 101/1942 Gainesville 100/1889 101/1899 100/1942 102/1942 99/1907 Alma, GA 102/2000 102/2002 104/2000 102/1942 100/1942 Craig Airport 98/1981 99/1993 100/2000 98/2015 99/1977

NOAA Jacksonville FL Office: Watches - Warnings - Advisories
FL...None. GA...None. AM...None.