Altamaha Sound, GA to Fernandina Beach, FL 20 - 60 NM Marine Forecast
|Today...South Winds 15 To 20 Knots Increasing To 20 To 25 Knots In The Afternoon. Seas Building To 4 To 6 Feet With A Dominant Period 5 Seconds. Chance Of Showers And Slight Chance Of Thunderstorms In The Morning, Then Showers And Chance Of Thunderstorms In The Afternoon.|
|Tonight...Southwest Winds 20 To 25 Knots. Seas 6 To 8 Feet With A Dominant Period 6 Seconds. Slight Chance Of Thunderstorms In The Evening. Slight Chance Of Showers.|
|Friday...Southwest Winds 20 To 25 Knots. Seas 6 To 8 Feet With A Dominant Period 6 Seconds. Chance Of Showers.|
|Friday Night...West Winds 15 To 20 Knots. Seas 5 To 7 Feet. Slight Chance Of Showers.|
|Saturday...West Winds 15 To 20 Knots. Seas 4 To 6 Feet.|
|Saturday Night...West Winds 15 To 20 Knots. Seas 4 To 6 Feet.|
|Sunday...Northwest Winds 10 To 15 Knots. Seas 3 To 5 Feet.|
|Sunday Night...North Winds 5 To 10 Knots. Seas 3 To 4 Feet.|
|Monday...North Winds 5 To 10 Knots. Seas 3 Feet.|
| AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm|
338 AM EDT Thu Oct 28 2021
A strong cold front will approach from the west today, preceded by showers and thunderstorms. A few these storms may be strong to severe this afternoon. Winds rapidly increase to Small Craft Advisory levels ahead of the front today. The front will press east to southeast of the area waters tonight, with elevated offshore winds through Friday night as strong low pressure continues north of the region. Winds should weaken Saturday night into Sunday as surface high pressure builds across the Gulf Coast region. The high will build north of the local waters early next week.
The approximate location of the west wall of the Gulf Stream as of Oct 28, 2021 at 1200 UTC...
- 52 nautical miles east northeast of Flagler Beach.
- 57 nautical miles east of Saint Augustine Beach.
- 68 nautical miles east of Jacksonville Beach.
- 88 nautical miles east southeast of St Simons Island.
| Area Forecast Discussion|
National Weather Service Jacksonville FL
725am EDT Thu Oct 28 2021
00am EDT]... .NEAR TERM [Today Through Tonight]... A strong mid/upper level trough per water vapor imagery and RAP analysis was located over the Plains with a closed 500 mb low over ern OK and warning AR. A cold front extended southward from a 995 mb low over AR to the central Gulf Coast with a band of strong to severe convection located over the Gulf of Mexico to the Gulf coastal plains. Locally, our airmass remains cool and dry for the moment with dewpoints in the upper 50s. A warm front was still located south of the area but will rapidly shift northward through the morning hours and be located in southeast GA by mid morning. Very strong height falls at 500 mb around 170-190 meters will work eastward to GA and Carolinas tonight as the trough swings eastward. Strengthening low level southerly flow ahead of the system and rapid moisture advection will bring the brunt of the band of convection to our area this morning and push through the forecast area midday into the mid to late afternoon hours. Models show moderate to strong bulk shear of 40-50 kt and MUCAPE values of 500-1500 J/kg across the area as the system translates eastward. This will support embedded supercells with possible damaging wind gusts, and isolated tornadoes given the 0-1 km helicity of 200-300. The main hindrance to severe weather episodes will be the limited instability as the low level inversion remains intact until about 13Z-14Z. Still looks like the best chance of a brief spin up is over northeast FL and perhaps coastal southeast GA is along the warm front as it pushes northward. Most of the deep convection expected to push offshore late afternoon but lingering wrap around moisture and the actual cold front will support a chance of showers well into the evening hours. Max temps today will be held down by clouds and precipitation with temps in the mid/upper 70s for southeast GA and upper 70s to lower 80s for northeast FL. Surface southerly winds up to 15-20 mph possible today ahead of the front but low level inversion and clouds may keep some areas in the 10-15 mph range. Behind the frontal passage for tonight, a bit cooler with min temps in the 50s and again being held in-check (being cooler) by the southwest to west winds of 10-15 mph and partly cloudy skies.
Short Term - Friday Through Saturday Night
Deep low pressure over the Tennessee Valley will move northeast along the Appalachians into the NE through the period. A tight pressure gradient will remain over the area producing strong gusty southwest to west winds. A post frontal trough will push across the area on Friday continuing the chance for showers as low level moisture persists. The pressure gradient will begin to relax along with winds Saturday night as the low pulls away from the southeast. Temperatures will be below average with highs in the upper 60/lower 70s and lows in the upper 40/lower 50s.
[Sunday through Wednesday]... Low pressure over the NE U.S. will move into the Canadian Maritimes while high pressure settles over the eastern seaboard. Winds will be light northwesterly on Sunday...becoming northeasterly early next week as the high moves east. The onshore flow will bring an increase in low level moisture with a slight chance of coastal showers along the NE Fl coast. Temperatures will be seasonal through the period.
A strong cold front and a band of convection will move through the area later today. Some of the showers and storms may be strong to severe this afternoon to early evening. Front should push offshore later tonight but lingering showers and a few storms will be possible in the unstable air over the warmer Atlantic waters. SCA (Small Craft Advisory) remains in effect for the area waters and no change was needed for the event times of SCA. There is a possibility that the nearshore waters will fall just shy of SCA (Small Craft Advisory) on Friday but not confident in dropping the SCA (Small Craft Advisory) during the Friday time frame in the 0-20 nm zone. Otherwise, elevated offshore winds through Friday night as strong low pressure continues north of the region. Winds weaken Saturday night into Sunday as surface high pressure builds across the Gulf Coast region. The high will build north of the local waters early next week. It is noteworthy that wave guidance shows the easterly swells being more energetic/more dominant sea on Friday with periods of about 12 seconds. The opposing wind waves from the westerly flow and these swells will make for very hazardous sea conditions.
Moderate risk expected today due to increasing south-southeast winds ahead of potent frontal system. Moderate risk forecast on Friday due to easterly swells, despite west/offshore wind.
Dispersion will be high on Friday across parts of NE Fl. Winds will be strong and gusty from the southwest with a chance of showers on Friday. Winds will gradually decrease over the weekend.
Locally heavy rainfall expected with the approaching convection today and main area of heaviest rainfall looks to be around the Suwannee Valley area. Rainfall amounts of 2-3 inches look possible in this area and included some storms may produce heavy rainfall in the today forecast for this area.
NOAA Jacksonville FL Office: Watches - Warnings - Advisories
FL...None. GA...None. AM...Small Craft Advisory from 1pm this afternoon to 8am EDT Saturday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM-Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM.
Small Craft Advisory from 1pm this afternoon to 8pm EDT Friday for Coastal waters from Altamaha Sound to Fernandina Beach FL out 20 NM-Coastal waters from Fernandina Beach to St. Augustine FL out 20 NM-Coastal waters from St. Augustine to Flagler Beach FL out 20 NM.