Marine Weather Net

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


REST OF TONIGHT

W
WINDS
10 - 15
KNOTS

THURSDAY

W
WINDS
10 - 15
KNOTS

THURSDAY NIGHT

SW
WINDS
10 - 15
KNOTS

FRIDAY

SW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
AMZ452 Forecast Issued: 751 PM EDT Wed Jul 08 2020

Rest Of Tonight...West Winds 10 To 15 Knots. Seas 1 To 2 Feet. Dominant Period 9 Seconds. Inland Waters A Light Chop. Showers Likely And A Slight Chance Of Thunderstorms Through The Night.
Thursday...West Winds 10 To 15 Knots Becoming South In The Afternoon. Seas 1 To 2 Feet. Dominant Period 8 Seconds. Inland Waters A Moderate Chop. A Chance Of Showers And Thunderstorms.
Thursday Night...West Southwest Winds 10 To 15 Knots. Seas 1 To 2 Feet. Dominant Period 8 Seconds. Inland Waters A Moderate Chop. A Chance Of Showers And Thunderstorms.
Friday...West Southwest Winds 5 To 10 Knots Becoming South In The Afternoon. Seas 1 To 2 Feet. Dominant Period 9 Seconds. Inland Waters A Light Chop. Showers And Thunderstorms Likely.
Friday Night...South Southwest Winds 5 To 10 Knots Becoming West Southwest 10 To 15 Knots After Midnight. Seas 1 To 2 Feet. Dominant Period 9 Seconds. Inland Waters A Light Chop. A Chance Of Showers And A Slight Chance Of Thunderstorms.
Saturday...West Southwest Winds 5 To 10 Knots Becoming South In The Afternoon. Seas 1 To 2 Feet. Dominant Period 9 Seconds. Inland Waters A Light Chop. Showers And Thunderstorms Likely.
Saturday Night...Southwest Winds 10 To 15 Knots. Seas 2 To 3 Feet. A Chance Of Showers And A Slight Chance Of Thunderstorms.
Sunday...South Southwest Winds 10 To 15 Knots. Seas 2 To 4 Feet. Showers And Thunderstorms Likely.
Sunday Night...Southwest Winds 10 To 15 Knots. Seas 2 To 4 Feet. A Slight Chance Of Showers.
Monday...South Southwest Winds 10 To 15 Knots. Seas 2 To 4 Feet. A Chance Of Showers And Thunderstorms.
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AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm
751 PM EDT Wed Jul 8 2020

Low pressure off the coast of the Carolinas will track north through Friday as surface high pressure lingers over the central Gulf of Mexico. A front trailing the departing surface low will linger across the southeast region through Saturday continuing elevated rain chances and prevailing offshore flow over the local waters. A weakening surface front will approach from the west late Sunday into Monday with an increase in southerly winds.

Gulf Stream
The approximate location of the west wall of the Gulf Stream as of Jul 07, 2020 at 1200 UTC...
- 65 nautical miles east northeast of Flagler Beach.
- 69 nautical miles east of Saint Augustine Beach.
- 76 nautical miles east of Jacksonville Beach.
- 91 nautical miles east southeast of St Simons Island.
Area Forecast Discussion
National Weather Service Jacksonville FL
915pm EDT Wednesday July 8 2020

No major changes to the forecast. Showers and storms are beginning to weaken and dissipate with the loss of daytime heating. Rain chances return tomorrow with northwesterly flow between ridging over the Gulf of Mexico and a broad upper trough over the eastern seaboard and a surface low over the Carolina coast tracking northward up the Atlantic coast. Temperatures will be around average with lows in the mid 70s and highs in the upper 80s to low 90s.

Near Term - Through Tonight
Behaved convection thus far this afternoon with stable conditions aloft (500 mb temps near -5 degC) and weak shear as a couple of troughs pivot SSE around the surface low near the SC Atlantic coast. Expect a few stronger cells capable of strong wet downburst winds (40-50 mph) through the afternoon and into the early evening across inland SE GA ahead of an approaching lobe of PVA now across SW GA. Another area of strong storm potential will focus across NE FL near the I-10 corridor, St. Johns River, eastward toward the Atlantic coast where boundary mergers will be maximized through early evening. NW storm motion will steadily push storms to the ESE with a general decrease in convective coverage and intensity after sunset with loss of diurnal instability. After midnight, there will be a chance of an inland shower given the very moist airmass still in place, but the best focus for early morning rain potential will shift back west toward the Gulf Coast region where the next short wave trough (firing convection over the central Gulf cost region will enhance convection moving inland under WNW steering. Some of this activity could near the I-75 corridor of our Suwannee River Valley zones through sunrise.

Temps will trend above normal with high dew pts making for muggy overnight conditions with lows in the low/mid 70s to upper mid/upper 70s near the St Johns River basin and Atlantic coast.

Long Term - Thursday Through Friday Night
Elevated rain chances continue under prevailing WNW steering flow between high pressure across the Gulf of Mexico and a deepening wake trough across the SE Atlantic coast in the wake of the surface low as it tracks northward along the US Atlantic seaboard. Convective pattern expected to be similar to today with morning showers and isolated storms edging inland from the GOMEX across our FL zones generally along and south of a GNV to SGJ line, then the focus afternoon storms will shift across SE GA, with activity shifting ESE toward the FL I-10 corridor into the evening and offshore of the local Atlantic coast. Convection will fade across SE GA and N FL into the evening, with a return of early morning activity edging inland form the GOMEX toward the I-75 corridor of the Suwannee River Valley through sunrise. Very high atmospheric moisture content with PWATs (Precipitable Waters) well above climo values up to 2.25" combined with warm, stable mid level temps and weak shear continue to support heavy rainfall as the main hazard, as well as locally strong wet downbursts with boundary mergers in storms mainly during the afternoon and evening hours.

A general warming trend in temperatures expected with highs nearing the low 90s across NE FL where more heating is expected in the afternoon with highs in the upper 80s to near 90 across SE GA before more widespread convection develops. Lows will trend above normal in the low to mid 70s. Very high dew pts combined with warmer daytime highs will also gradually increase peak heat index values back near 105 degF to 110 degF for some areas Friday. f

Long Term - Saturday Through Wednesday
Sat & Sun...Mid level trough axis edges east of the area Sat with drier air filtering over SE GA from the WNW Sat afternoon which will bring lower rain chances into the weekend. Best chances of mainly afternoon and evening showers/storms will focus across NE FL with activity moving inland earlier in the day south of the I-10 corridor under prevailing WNW steering flow. With drier air across SE GA favoring more heating, high temps expected to rise above normal into the mid 90s with low 90s across NE FL with heat index values ranging from 105-110 degF each afternoon even toward the beaches.

Monday through Wed...Elevated rain chances return early next week with higher moisture returning between surface fronts north of the region and high pressure across south FL. This pattern will once again bring an early start to rain across our western zones under prevailing westerly flow with convection expanding in coverage and intensity as it tracks eastward into the afternoon and early evening. Temperature will be near normal values.


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