Marine Weather Net

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


TONIGHT

SW
WINDS
15 - 20
KNOTS

TUESDAY

SW
WINDS
15 - 20
KNOTS

TUESDAY NIGHT

SW
WINDS
15 - 20
KNOTS

WEDNESDAY

SW
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
AMZ472 Forecast Issued: 913 PM EDT Mon Jun 21 2021

SMALL CRAFT EXERCISE CAUTION
Tonight...Southwest Winds 15 To 20 Knots. Seas 3 To 5 Feet With A Dominant Period 4 Seconds. Chance Of Showers And Slight Chance Of Thunderstorms.
Tuesday...Southwest Winds 15 To 20 Knots. Seas 3 To 5 Feet With A Dominant Period 5 Seconds. Showers Likely And A Chance Of Thunderstorms.
Tuesday Night...Southwest Winds 15 To 20 Knots Diminishing To 10 To 15 Knots After Midnight. Seas 3 To 5 Feet With A Dominant Period 9 Seconds. Chance Of Showers And Slight Chance Of Thunderstorms.
Wednesday...Southwest Winds 10 To 15 Knots Becoming South 5 To 10 Knots In The Afternoon. Seas 3 To 4 Feet. Chance Of Showers And Slight Chance Of Thunderstorms.
Wednesday Night...South Winds 5 To 10 Knots. Seas 2 To 3 Feet. Chance Of Showers And Slight Chance Of Thunderstorms.
Thursday...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. Showers Likely And Slight Chance Of Thunderstorms.
Thursday Night...Southeast Winds 5 To 10 Knots. Seas 2 To 3 Feet. Chance Of Showers And Thunderstorms.
Friday...Southeast Winds 5 To 10 Knots. Seas 3 To 4 Feet. Chance Of Showers And Thunderstorms.
Friday Night...Southeast Winds 10 To 15 Knots. Seas 3 To 4 Feet. Slight Chance Of Showers And Thunderstorms.
Saturday...Southeast Winds 10 Knots. Seas 3 To 5 Feet. Slight Chance Of Showers And Thunderstorms.
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AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm
913 PM EDT Mon Jun 21 2021

A cold front approaching the Southeastern United States will dive southeastward and approach the Georgia waters on Tuesday night and will stall near the Florida border from Wednesday through around Friday. Southwesterly winds near Caution levels will linger tonight and will remain breezy through Tuesday night. Showers and thunderstorms will impact our local waters each day through the weekend. A light onshore wind will develop late this week as strong high pressure over the Canadian Maritime region wedges down the southeastern seaboard.

Gulf Stream
The approximate location of the west wall of the Gulf Stream as of Jun 17, 2021 at 1200 UTC...
- 60 nautical miles east northeast of Flagler Beach.
- 68 nautical miles east of Saint Augustine Beach.
- 81 nautical miles east of Jacksonville Beach.
- 98 nautical miles east southeast of St Simons Island.
Area Forecast Discussion
National Weather Service Jacksonville FL
922pm EDT Monday Jun 21 2021

...LOCALLY HEAVY RAINFALL AND ISOLATED SEVERE WEATHER THREAT EXPECTED ACROSS NE FL/SE GA ON TUESDAY... Convection has faded early this evening and has left just isolated showers/sprinkles across the region in the moist Southwest steering flow ahead of the approaching cold front over the SE US. Models struggling to latch onto next round of convection with earlier 12z runs trying to show widespread convection late tonight or towards early Tuesday morning, but now the 18Z runs and more recently the latest Hi-Res models have backed off this solution somewhat and have delayed the next significant round of showers and storms until the mid-late morning hours on Tuesday. For now have continued the rapid increase in probability of precipitation Tuesday morning to 60-90% with locally heavy rainfall and gusty winds the main threat from bands of convection moving out of the NE Gulf of Mexico or west along the I-10 corridor. Overall the story is the same for Tuesday a rather wet and cooler than normal day for late June with highs only in the lower to middle 80s. Long enough breaks in the heavy rainfall over recent days should allow another day of heavy rainfall without any significant flooding issues except for urban areas of NE FL where isolated flash flooding will be possible on Tuesday.

.NEAR TERM [Through Tuesday]... An upper trough digging into the Tennessee and Ohio valleys tonight and into southern Georgia on Tuesday will push a cold front into the Deep South Tuesday afternoon into evening. Multiple shortwaves moving over the region will support waves of convection tonight into Tuesday. Deep southwesterly flow will continue to advect a tropical air mass into our area from the northeast Gulf of Mexico tonight into Tuesday with PWATs (Precipitable Waters) in the 2 - 2.2 inch range. Showers and storms continue to move off the northeastern Gulf of Mexico and across northeast Florida into Tuesday. A slight reprieve from showers and storms tonight, however, another wave of convection will move up from the northeastern Gulf and overspread across the Suwannee Valley and inland southeast GA progressing across the area in the morning hours. Temperatures aloft will slowly cool off on Tuesday, increasing the potential for strong to isolated severe thunderstorms that will be capable of producing downburst winds of 40-60 mph in the afternoon. Heavy rainfall will be likely with storms that move through causing a potential for flash flooding especially across areas that previously received rainfall today. Low temperatures tonight will be around normal in the low to mid 70s and highs tomorrow will be below normal in the 90s.

.SHORT TERM [Tuesday Night Through Wednesday Night]... High pressure pressure to the southeast moves away from the region as high pressure builds in to the north-northeast. A trough digs into southeast Georgia Tuesday night, lifts and moves eastward through Wednesday as a cool front will moves into southeast Georgia Tuesday night and stalls over northeast Florida later on Wednesday. Due to prevailing southwest flow ushering in moisture off the Gulf, a lingering moist airmass (PWATs (Precipitable Waters) around 2 inches) will support showers and storms moving from west to east along the frontal boundary across the area through the day. Southwest flow will also push the Gulf coast sea breeze well inland. Cloudy skies will keep lows near normal in the upper 60s to low 70s and highs below normal in the 80s.

.LONG TERM [Thursday Through Sunday]... A stalled frontal boundary will linger over the area through Friday before dissipating. High pressure will build to the northeast causing the flow to shift to the east-southeast. This will allow the east coast sea breeze to become dominant and push well inland each afternoon. Daily rounds of convection are expected this period due to diurnal instability and sea breeze convergence. Low temperatures will be near normal in the upper 60s to low 70s. Highs will be below normal and increase into the weekend to near normal in the 80s and low 90s.

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