Fernandina Beach to St. Augustine, FL Out 20 NM Marine Forecast
|Today...East Winds 5 To 10 Knots Increasing To 10 To 15 Knots In The Late Morning And Afternoon. Seas 2 To 3 Feet With A Dominant Period 7 Seconds. A Moderate Chop On The Intracoastal Waters. Chance Of Showers And Slight Chance Of Thunderstorms In The Morning, Then Showers Likely And Chance Of Thunderstorms In The Afternoon.|
|Tonight...Southeast Winds 10 To 15 Knots Diminishing To 5 To 10 Knots After Midnight. Seas 2 To 3 Feet With A Dominant Period 9 Seconds. A Light Chop On The Intracoastal Waters. Showers Likely In The Evening. Slight Chance Of Thunderstorms. Chance Of Showers After Midnight.|
|Monday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet With A Dominant Period 9 Seconds. A Light Chop On The Intracoastal Waters. Showers And Slight Chance Of Thunderstorms.|
|Monday Night...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. Mostly Smooth On The Intracoastal Waters. Showers Likely In The Evening. Slight Chance Of Thunderstorms. Chance Of Showers After Midnight.|
|Tuesday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. A Light Chop On The Intracoastal Waters. Showers Likely In The Morning. Slight Chance Of Thunderstorms. Showers In The Afternoon.|
|Tuesday Night...South Winds 5 To 10 Knots Becoming Southwest After Midnight. Seas 2 To 3 Feet. Chance Of Showers And Slight Chance Of Thunderstorms.|
|Wednesday...South Winds 5 To 10 Knots. Seas 2 To 3 Feet. Showers Likely And Chance Of Thunderstorms.|
|Wednesday Night...Southwest Winds 5 To 10 Knots Becoming Northwest After Midnight. Seas 2 To 3 Feet. Chance Of Showers And Thunderstorms.|
|Thursday...North Winds 10 To 15 Knots. Seas 3 To 4 Feet. Slight Chance Of Showers And Thunderstorms.|
| AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm|
934 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.
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
925am EDT Sunday September 19 2021
...LOCALIZED HEAVY RAIN AND FLOODING POSSIBLE TODAY MAINLY OVER PORTIONS OF NORTHEAST FL...
Forecast remains on track, no major updates made at this time. Showers have been moving onshore in SE GA and north of St. Augustine in NE FL. The Lightning threat this morning is low but a few cells have produced a few lightning strikes near the coast and over the coastal waters. Showers will continue to move inland throughout the morning, then numerous showers and thunderstorms will be possible area-wide this afternoon and evening. The 12Z Jacksonville upper air sounding measured PWAT (Precipitable Water) values well above average, which will result in another day of heavy rainfall and potential flooding. The heaviest rainfall is expected to be generally between I-95 and I-75 in Northeast Florida. Locations along the I-75 corridor will be especially susceptible to flooding due to rain falling on saturated soils from heavy rainfall received in this area over the past few days. Runoff could also exacerbate ongoing river flooding along the Santa Fe River. Expected precipitation and cloud cover will keep high temperatures in the middle 80s today.
42am 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.
NOAA Jacksonville FL Office: Watches - Warnings - Advisories
FL...None. GA...None. AM...None.