Marine Weather Net

St. Augustine to Flagler Beach, FL 20 - 60 NM Marine Forecast


5 - 10


10 - 15


10 - 15


5 - 10

The Marine Weather Forecast In Detail:
AMZ474 Forecast Issued: 320 AM EDT Sun Sep 19 2021

Today...East Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Late Morning And Afternoon. Seas 2 To 4 Feet With A Dominant Period 7 Seconds. Chance Of Showers And Slight Chance Of Thunderstorms.
Tonight...Southeast Winds 10 To 15 Knots. Seas 3 To 4 Feet With A Dominant Period 9 Seconds. Showers Likely And Slight Chance Of Thunderstorms.
Monday...Southeast Winds 10 To 15 Knots. Seas 3 To 4 Feet With A Dominant Period 8 Seconds. Showers And Slight Chance Of Thunderstorms.
Monday Night...Southeast Winds 5 To 10 Knots. Seas 3 To 5 Feet. Showers Likely And Slight Chance Of Thunderstorms.
Tuesday...Southeast Winds 5 To 10 Knots. Seas 3 To 5 Feet. Showers And Slight Chance Of Thunderstorms.
Tuesday Night...Southeast Winds 10 Knots Becoming South 5 To 10 Knots After Midnight. Seas 3 To 5 Feet. Showers Likely And Slight Chance Of Thunderstorms.
Wednesday...Southwest Winds 5 To 10 Knots. Seas 3 To 5 Feet. Chance Of Showers And Thunderstorms.
Wednesday Night...Southwest Winds 5 To 10 Knots Becoming Northwest 10 Knots After Midnight. Seas 3 To 5 Feet. Chance Of Showers And Thunderstorms.
Thursday...North Winds 10 To 15 Knots. Seas 4 To 6 Feet. Slight Chance Of Showers And Thunderstorms.
SHARE THIS PAGE:           
AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm
320 AM EDT Sun Sep 19 2021

A trough of low pressure will develop along the northeast Florida and southeast Georgia coasts today and persist through Wednesday. Abundant tropical moisture and the trough will continue to enhance daily shower and thunderstorm chances across area waters the next few days. A cold front will then enter the southeastern states towards midweek, passing through our waters late Wednesday night, followed by increased north winds on Thursday.

Gulf Stream
The approximate location of the west wall of the Gulf Stream as of Sep 18, 2021 at 1200 UTC...
- 47 nautical miles east of Flagler Beach.
- 60 nautical miles east southeast of Saint Augustine Beach.
- 76 nautical miles east of Jacksonville Beach.
- 94 nautical miles east of St Simons Island.
Area Forecast Discussion
National Weather Service Jacksonville FL
742am EDT Sunday September 19 2021

58am EDT]... Near Term - Through Tonight
Current guidance suite continues to show weak west-east low level troughing from the eastern Gulf coast, through north central FL and then into the our southern marine waters off of Flagler and St Johns county. This weak boundary will remain quasi-stationary today and then begin to lift slowly northward later tonight. Moisture remains high over most zones with widespread PWATs (Precipitable Waters) of 2+ inches through tonight, and a weak east-northeast low level flow persists as high pressure ridge remains from GA northeastward to New England. This setup will favor initial convection again along the coastal areas through the morning hours, with convection oriented in cells or northwest-southeast bands due to uniform east- southeast flow through about 12 kft. With a mid level trough from the central FL panhandle southeast into northeast FL, slow storm motion and positive vorticity advection will again support numerous to widespread showers and storms to mainly inland northeast FL. Areas of heavy rainfall and localized flooding may develop again and have included heavy rainfall wording in the grids. Abundant clouds and precipitation area will keep highs a bit lower than the past couple of days with highs mainly in the mid 80s.

Tonight...deep layered moisture and leftover boundaries will support scattered to numerous showers and storms this evening, eventually weakening overnight with loss of heating. Focus after 1-2am will be more toward the coastal areas again, especially from St Augustine to Brunswick but with more inland progress over inland southeast GA. Patchy late night fog will be possible and lows around 71-75 deg are expected.

.SHORT TERM [Monday Through Tuesday]... A developing coastal trough may produce bands of heavy rainfall especially along the se Ga coast where onshore flow and convergence will increase as strong high pressure builds over the ne U.S. Heavy rainfall may also occur over inland northeast Florida during the afternoon/evening hours as onshore winds push the east coast seabreeze well inland. Deep moisture and weak steering winds will continue the chance for localized flooding.

.LONG TERM [Wednesday Through Saturday]... An approaching upper trough and cold front to the nw will produce a sw-w flow over the area on Wednesday maintaining the very moist and unstable airmass over the area. Showers and thunderstorms will be likely with the continued threat of heavy rainfall and localized flooding due to PWATs (Precipitable Waters) near 2 inches and a slow storm motion. The cold front will push se across se Ga Wednesday night and northeast Florida early Thursday morning bringing drier air and lower rain chances. Surface high pressure will build to the north of the area which will result in a northeast flow into the weekend. Coastal convergence and low level moisture behind the front will produce a chance for mainly coastal showers near the northeast Florida coast Thu- Sat...with dry conditions expected across se Ga. Cooler and less humid conditions behind the front will result in low temperatures falling into the low/mid 60s well inland.

Variable to light east winds early today will increase to near 10-15 kt by the afternoon hours. Seas are a bit lower than NWPS so slight adjustments were made to the 1st period. Otherwise, winds tonight will transition to east-southeast tonight and then southeast on Monday as coastal troughing, oriented more north to south, develops, and more or less persists into Wednesday. The abundant moisture, and convergence flow in the low levels will support daily showers and storms over the area waters. A cold front moves in late Wednesday night, with a northerly flow anticipated by Thursday as the front slides just south of the area waters.

Rip Currents
Moderate risk of rip currents will continue today through Monday due to onshore flow and easterly swells. Some longer period swell is noted around 13 seconds today.


Minor flooding continues along lower portions of the Santa Fe River near the Three Rivers Estates gauge. Runoff from numerous to widespread convection will likely result in river rises across portions of northeast FL. It is possible additional river flood warnings may be needed, especially along the Santa Fe River where heavy rains fell late Saturday.

Locally heavy rainfall and localized flooding will be possible over the next few days with WPC showing marginal risk of excessive rainfall. Estimated rainfall amounts into Monday are around 1-2 inches, with locally higher totals possible. Heaviest amounts in the today- Monday time period look to be over northeast FL and possibly coastal southeast GA.

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