Marine Weather Net

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


THIS AFTERNOON

NW
WINDS
15
KNOTS

TONIGHT

NNE
WINDS
10 - 15
KNOTS

THURSDAY

E
WINDS
15
KNOTS

THURSDAY NIGHT

SE
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
AMZ454 Forecast Issued: 949 AM EST Wed Dec 02 2020

This Afternoon...Northwest Winds Around 15 Knots, Becoming Northerly This Afternoon. Seas 2 To 4 Feet With A Dominant Period Of 5 Seconds. A Moderate Chop On The Intracoastal Waters.
Tonight...North Northeast Winds 10 To 15 Knots. Seas 3 To 4 Feet With A Dominant Period Of 4 Seconds. A Light Chop On The Intracoastal Waters.
Thursday...East Winds Around 15 Knots. Seas 3 To 4 Feet With A Dominant Period Of 5 Seconds. A Moderate Chop On The Intracoastal Waters.
Thursday Night...Southeast Winds 10 To 15 Knots, Diminishing To 5 To 10 Knots After Midnight. Seas 3 To 4 Feet. Becoming Mostly Smooth On The Intracoastal Waters.
Friday...South Winds 5 To 10 Knots, Becoming South Southeast 10 To 15 Knots During The Afternoon. Seas 3 To 4 Feet. A Light Chop On The Intracoastal Waters. Slight Chance Of Showers Late In The Afternoon.
Friday Night...Southwest Winds 10 To 15 Knots. Seas 3 To 4 Feet. Chance Of Showers And Slight Chance Of Thunderstorms.
Saturday...West Winds 10 To 15 Knots. Seas 3 To 4 Feet. Slight Chance Of Showers.
Saturday Night And Sunday...West Northwest Winds Around 15 Knots. Seas 2 To 3 Feet.
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AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm
949 AM EST Wed Dec 2 2020

High pressure centered over the southeastern states will move slowly eastward, shifting offshore of the Carolina coast on Thursday afternoon in advance of weak low pressure that will migrate eastward along the northern Gulf coast. This low pressure center will then pivot northeastward across the southern Appalachians while strengthening on Friday night, dragging a cold front across our local waters early on Saturday morning. A reinforcing dry cold front will then move across our waters on Sunday night and Monday morning.

Gulf Stream
The approximate location of the west wall of the Gulf Stream as of Dec 01, 2020 at 1200 UTC...
- 51 nautical miles east of Flagler Beach.
- 61 nautical miles east of Saint Augustine Beach.
- 72 nautical miles east of Jacksonville Beach.
- 88 nautical miles east southeast of St Simons Island.
Area Forecast Discussion
National Weather Service Jacksonville FL
1031am EST Wednesday Dec 2 2020

...AREAS OF FROST EXPECTED TONIGHT FOR LOCATIONS ALONG AND WEST OF U.S. HIGHWAY 301...

Late morning surface analysis depicts arctic high pressure (1030 millibars) centered over the Tennessee Valley and the southeastern states. Meanwhile, weak low pressure was developing along the Red River Valley of northeastern Texas, with a frontal system taking shape over the Texas Hill Country. Aloft...zonal flow is developing along the northern Gulf coast as deep troughing progresses across New England. Meanwhile, troughing was cutting off from the main flow pattern over the Texas and Oklahoma panhandles. The developing zonal flow pattern was advecting a thin cirrus shield east-northeastward over our region. Otherwise, a very dry air mass prevails over our region, with the morning soundings at Jacksonville and Tallahassee registering daily record low PWAT (Precipitable Water) values of less than 0.15 inches. The cold and dry air mass over our region resulted in low temperatures falling to the mid and upper 20s at most inland locations, with mid 30s observed at coastal locations. Inland lows were generally a few degrees above daily record lows for December 2nd. Temperatures at 15Z were recovering into the 40s region-wide, with dewpoints in the 20s.

High pressure will slowly weaken as it remains centered over the southeastern states through tonight. A weak coastal trough will take shape over our near shore waters overnight, resulting in stratocumulus developing and moving onshore along the northeast FL coast late tonight. Otherwise, cirrus will only gradually thicken over our skies this evening through Thursday as a jet streak embedded in the zonal flow pattern traverses the Ozarks. Cold air advection will continue through early this afternoon before low level flow veers to north-northeasterly. Highs will generally reach the 55-60 degree range region-wide, which is about 10-15 degrees below early December climatology. The developing coastal trough overnight will create a larger temperature gradient across our area, as light northerly winds keep coastal lows in the low to mid 40s, while inland lows fall to the low and mid 30s. Areas of frost are expected for locations along and west of U.S. Highway 301 overnight and early on Thursday morning. Low temperatures at coastal locations will likely occur around midnight, as increasing stratocumulus and developing low level northeasterly winds result in temperatures rising through the 40s and towards 50 degrees during the predawn hours for locations east of I-95.

Marine
High pressure centered over the southeastern states will move slowly eastward, shifting offshore of the Carolina coast on Thursday afternoon in advance of weak low pressure that will migrate eastward along the northern Gulf coast. This low pressure center will then pivot northeastward across the southern Appalachians while strengthening on Friday night, dragging a cold front across our local waters early on Saturday morning. Small Craft will need to Exercise Caution if venturing into the offshore waters today, where seas of 4-6 feet will prevail. A reinforcing dry cold front will then move across our waters on Sunday night and Monday morning. Stronger offshore winds and building seas in the wake of these frontal passages may result in Caution conditions offshore late this weekend and early next week.

Rip Currents
Mainly offshore to side shore winds will keep the rip current risk low today. Breezy onshore winds will result in a moderate risk at the northeast FL beaches on Thursday, with a long period easterly ocean swell arriving on Friday and creating a moderate risk at all area beaches.

Fire Weather
North-northwesterly surface and transport winds sustained at 10-15 mph will shift to northerly this afternoon. Long durations of critically low humidity values are expected at most inland locations this afternoon, with marginally low dispersion values also expected. Surface and transport winds will veer to northeasterly overnight and then easterly by Thursday morning, resulting in higher humidity and dispersion values tomorrow area- wide.

.SHORT TERM [Thursday Through Saturday]... High pressure will be northeast of the region Thursday and Thursday night, with a resultant onshore flow, and continued dry weather. Temperatures will be milder due to the onshore flow. Highs Thursday will range from the mid 60s north of Alma, GA to the lower 70s south of Jacksonville.

The high will move more toward the east northeast Friday, as a wave of low pressure moves northeast toward the region from the gulf. This wave will develop into a low to the northwest Friday afternoon, with its associated cold front moving southeast across forecast area Friday night. Moisture will increase across the region Friday, with a chance for a few showers in the afternoon. The best chance for day time showers will be well inland. The chance will increase Friday night, as moisture pools along the front. With convergence along the boundary, could see a few storms develop, but limited instability given nocturnal passage. Temperatures will continue on the mild side Friday into Friday night on south southeast flow, with readings above normal.

For Saturday, the front should be to the east southeast Saturday morning, but could see a few showers linger over eastern counties. High pressure will build from the west Saturday afternoon, so much of Saturday is expected to be dry, with sunshine increasing. Temperatures will be slow to rise Saturday, given cold advection, but sunshine should get readings into the 60s.

.LONG TERM [Saturday Night Through Tuesday]... The region will be between high pressure to the southwest and low pressure to the northeast through Sunday, with dry weather and a cool airmass expected. A cold front will move southeast across the area Monday into Monday night. While this passage is expected to be dry, it will usher in a reinforcement of the cooler than normal airmass. High pressure will build from the northwest Tuesday, with dry weather continuing.

Temperatures will be below normal throughout this period.

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