Fernandina Beach to St. Augustine, FL Out 20 NM Marine Forecast
|Rest Of Today...West Northwest Winds 15 To 20 Knots, Diminishing To 10 To 15 Knots In The Afternoon. Seas 2 To 3 Feet With A Dominant Period Of 3 Seconds. Becoming A Light Chop On The Intracoastal Waters.|
|Tonight...Northwest Winds 5 To 10 Knots. Seas 2 To 3 Feet With A Dominant Period Of 9 Seconds. Mostly Smooth On The Intracoastal Waters.|
|Tuesday...North Winds 5 To 10 Knots, Becoming East In The Afternoon. Seas 1 To 2 Feet With A Dominant Period 9 Seconds. Mostly Smooth On The Intracoastal Waters.|
|Tuesday Night...South Winds 5 To 10 Knots, Becoming West After Midnight. Seas 1 To 2 Feet. Mostly Smooth On The Intracoastal Waters.|
|Wednesday...West Winds 5 To 10 Knots. Seas 1 To 2 Feet. Mostly Smooth On The Intracoastal Waters.|
|Wednesday Night...Northwest Winds 5 To 10 Knots. Seas 1 To 2 Feet.|
|Thursday...West Winds 5 To 10 Knots, Becoming Southwest In The Afternoon. Seas 1 To 2 Feet.|
|Thursday Night...Southwest Winds 10 To 15 Knots. Seas 2 To 3 Feet. Chance Of Showers.|
|Friday...Southwest Winds 10 To 15 Knots, Becoming West 5 To 10 Knots In The Afternoon. Seas 2 To 3 Feet. Chance Of Showers.|
| AMZ400: Synopsis for Altamaha Sound GA to Flagler Beach FL out to 60 nm|
828 AM EST Mon Jan 18 2021
A trough will move offshore this morning, with high pressure then building directly over our waters late tonight and Tuesday. Gusty west-northwesterly winds this morning will diminish this afternoon. Another trough will approach the Georgia waters from the north on Wednesday and will then dissipate as weak high pressure builds over the Florida peninsula late Wednesday night and Thursday. Low pressure will then develop over eastern Texas on Thursday night and will move quickly eastward across the Deep South on Friday, pushing a cold front southward across our local waters on Friday night. This front will then stall over the Florida peninsula during the weekend as strong high pressure builds southeastward from the Great Lakes region into the Ohio Valley and wedges down the southeastern seaboard.
The approximate location of the west wall of the Gulf Stream as of Jan 16, 2021 at 1200 UTC...
- 58 nautical miles east of Flagler Beach.
- 63 nautical miles east of Saint Augustine Beach.
- 71 nautical miles east of Jacksonville Beach.
- 92 nautical miles east southeast of St Simons Island.
| Area Forecast Discussion|
National Weather Service Jacksonville FL
923am EST Monday Jan 18 2021
...ELEVATED FIRE DANGER THIS AFTERNOON... ...LIGHT FREEZE INLAND LATE TONIGHT WITH FROST EXTENDING TO COASTAL LOCATIONS... Mid-morning surface analysis depicts a weak trough pushing eastward across our local coastal waters, with high pressure (1022 millibars) centered over the lower Mississippi Valley in the wake of this trough. Aloft...a shortwave trough was pivoting eastward across the Mid-Atlantic states, with the base of this trough extending southward along the southeastern seaboard. Brisk low level westerly flow was located in the lower levels per the morning soundings at Jacksonville and Tallahassee, where speeds were in the 25-30 knot range around 1000 feet off the ground. Skies have cleared out area-wide, and breezy northwesterly surface winds were already developing along the northeast FL coast. Temperatures at 14Z were rising through the 40s, with a drier air mass plunging into southeast GA in the wake of the departing trough, were dewpoints were falling through the 30s, with dewpoints generally in the upper 30s and lower 40s across northeast and north central FL.
A dry and seasonably cool air mass will filter into our region this afternoon as high pressure begins to strengthen as it moves eastward along the northern Gulf coast. Model soundings indicate that low level westerly flow will veer to west-northwesterly with gradually decreasing speeds this afternoon. However, breezy conditions are expected to overspread inland locations by the late morning and early afternoon hours as full insolation mixes the lower troposphere, and these breezy conditions will coincide with a rapid drop in humidity values to create an elevated fire danger during the early and mid afternoon hours. The increasingly dry air mass and full sunshine will counter weak cold air advection, and highs will climb to the 60-65 degree range, which is near climatology for our area.
High pressure will then settle directly over our region from the west overnight, resulting in ideal radiational cooling conditions by the predawn and early morning hours. We have issued Frost Advisories for inland locations to the east of the existing Freeze Warning and also for coastal portions of Nassau County. Lows will generally range from 30-35, except upper 30s at the northeast FL beaches. Frost will extend into coastal locations by sunrise on Tuesday. High pressure will remain overhead on Tuesday as flow aloft becomes zonal, and temperatures will generally rise to the mid 60s, with a few upper 60s in north central FL.
A trough will move offshore this morning, with high pressure then building directly over our waters late tonight and Tuesday. Gusty west-northwesterly winds this morning will diminish this afternoon. Small Craft should Exercise Caution until wind speeds diminish later this afternoon. Seas of 3-5 feet offshore will gradually subside overnight, with 2-3 foot seas expected near shore. Another trough will approach the Georgia waters from the north on Wednesday and will then dissipate as weak high pressure builds over the Florida peninsula late Wednesday night and Thursday. Low pressure will then develop over eastern Texas on Thursday night and will move quickly eastward across the Deep South on Friday, pushing a cold front southward across our local waters on Friday night. This front will then stall over the Florida peninsula during the weekend as strong high pressure builds southeastward from the Great Lakes region into the Ohio Valley and wedges down the southeastern seaboard.
A low risk will continue for much of this week due to prevailing offshore winds and decreasing wave heights.
Breezy west-northwesterly transport winds this morning will shift to westerly this afternoon. West-northwesterly surface winds will remain sustained at 5-10 mph this morning and will shift to westerly towards noon, with sustained speeds increasing to 10-15 mph with occasional gusts around 20 mph through the mid-afternoon hours. These breezy winds will create marginally high dispersion values across most of our region by early afternoon. Relative humidity values will plunge to critical values early this afternoon, and these factors along with fuel moisture levels just below Red Flag Criteria will create an elevated Fire Danger this afternoon, especially across northeast and north central Florida. Surface and transport winds will then rapidly diminish this evening and will continue through Tuesday, resulting in low daytime dispersion values.
Near Term - Through Tonight
Mid-upper level trough will swing through the area today and will be accompanied by some mid clouds over southeast GA early today. Weak front/surface trough will push through the area early this morning but conditions will remain dry today with sunny skies. Surface high pressure will build in from the west today and be centered over northeast FL tonight. Highs today expected to be in the upper 50s for southeast GA, and upper 50s to lower 60s over northeast FL. Continued to favor a blend of guidance for high temps as it seemed to verify better the past couple of days. Occasional breezy westerly winds with gusts around 20 mph, possibly a little higher, as deep boundary layer mixing occurs.
Tonight...clear skies and winds going to calm will lead to excellent radiational cooling conditions. Went a couple of degrees below MOS and NBM guidance for lows with min temps in the lower 30s common, mainly inland areas. This results in 2-4 hrs of freezing conditions for a few counties in northeast FL. A freeze warning has been hoisted as a result. Some frost looks likely for other zones southeast of the freeze warning but will let dayshift take another look at the forecast as daytime drying today may lead to lower dewpoints and drier low level airmass for tonight.
.SHORT TERM [Tuesday Through Wednesday]... Surface high pressure will be overhead on Tuesday keeping the region dry with clear skies. On Wednesday, high pressure slides to the west as a weak cold front moves southeast into the area. The front is expected to be dry and will bring an increase in cloud cover. Temperatures begin to moderate to near to above normal with highs in the 60s and lows in the upper 30s and 40s.
Long Term - Thursday Through Monday
A quasi-stationary front sets up across the Southeastern states Thursday into Friday. On Thursday into Friday, impulses will move east along the frontal boundary increasing cloud cover and a chance for showers. The associated low will move across the boundary and pass to the north on Friday. High pressure building in from the north will push the boundary south of the area Friday night into Saturday. Best chance for showers will be mainly southeast Georgia and the I-10 corridor in northeast Florida Thursday night into Friday night. Temperatures will be above normal through the weekend with highs in the 60s and 70s and lows in the 40s and 50s.
NOAA Jacksonville FL Office: Watches - Warnings - Advisories
FL...Frost Advisory from 2am to 9am EST Tuesday for Central Marion- Coastal Nassau-Eastern Marion-Inland Flagler-Inland St. Johns-Putnam.
Freeze Warning from 2am to 9am EST Tuesday for Bradford-Clay- Eastern Alachua-Inland Duval-Inland Nassau-Western Alachua- Western Marion.