Savannah, GA to Altamaha Sound, GA including Grays Reef National Marine Sanctuary Marine Forecast
|Tonight...Se Winds 5 To 10 Kt. Seas 1 To 2 Ft.|
|Sat...Se Winds 5 To 10 Kt. Seas 2 Ft. A Slight Chance Of Showers In The Afternoon.|
|Sat Night...Se Winds 5 To 10 Kt. Seas 2 To 3 Ft. A Chance Of Showers With A Slight Chance Of Tstms After Midnight.|
|Sun...S Winds 10 To 15 Kt With Gusts To 25 Kt. Seas 3 To 4 Ft. A Slight Chance Of Tstms. A Chance Of Showers In The Morning, Then Showers In The Afternoon.|
|Sun Night...Sw Winds 20 To 25 Kt, Becoming Nw After Midnight. Gusts To 35 Kt. Seas 4 To 6 Ft, Subsiding To 4 To 5 Ft After Midnight. Showers With A Slight Chance Of Tstms In The Evening, Then A Slight Chance Of Showers After Midnight.|
|Mon...Nw Winds 15 To 20 Kt With Gusts To 30 Kt, Becoming N 10 To 15 Kt In The Afternoon. Seas 3 To 4 Ft, Subsiding To 2 Ft In The Afternoon.|
|Mon Night...N Winds 10 To 15 Kt. Seas 2 To 3 Ft.|
|Tue...Ne Winds 15 Kt. Seas 3 To 4 Ft.|
|Tue Night...Ne Winds 15 To 20 Kt. Seas 3 To 4 Ft.|
|Wed...Ne Winds 15 To 20 Kt. Seas 4 To 5 Ft.|
|Wed Night...Ne Winds 15 To 20 Kt. Seas 4 To 6 Ft. Winds And Seas Higher In And Near Tstms.|
| Area Forecast Discussion|
National Weather Service Charleston SC
304pm EST Fri Dec 8 2023
High pressure will prevail through Saturday. A strong cold front will cross the area on Sunday, followed by high pressure next week.
Near Term - Until 6am Saturday Morning
Tonight: High pressure over the Atlantic will continue to extend into the region through the overnight period ahead of a cold front moving into the mid Mississippi Valley. Model guidance suggests subtle convergence will develop across the coastal waters later tonight, helping to generate isolated shower activity offshore. Land areas are expected to stay dry, though it isn't out of the question for a shower to brush the Charleston County coast. Cloud cover should increase through the evening as a shortwave passes through in the southwest flow aloft, before decreasing in coverage as sunrise Saturday approaches. Lows are forecast to fall into the upper 40s across the interior counties, ranging to the low to mid 50s closer to the coast.
Short Term - 6am Saturday Morning Through Monday
Saturday: Surface high pressure will shift offshore of the Southeast U.S. through Saturday night as the main upper-level ridge axis propagates to the east. A warm, southerly flow on the backside of the high will support a slowly increase in moisture with PWATs (Precipitable Waters) climbing >1.25". A few showers associated with a weak coastal trough just offshore could skirt parts of the lower/middle South Carolina coast through the day as pockets of channeled vorticity embedded in the southwest flow aloft traverse the area, but no major impacts are expected. Rain chances will start to ramp up early Sunday morning as a broad corridor of warm air advection ahead of an approaching cold front spreads east into the Carolinas and Georgia. While the better rain chances will hold off until Sunday, some degree of scattered shower activity will likely impact parts of the area prior to daybreak with signals that the highest coverage could be centered along the South Carolina coast. probability of precipitation were adjusted slightly to reflect this thinking. Highs will warm into the mid- upper 70s Saturday afternoon with lows Sunday morning only dropping into the lower 60s for most areas.
Sunday: Sunday has the potential to be quite active with a number of potential impacts. Guidance is consistent in showing a strong upper trough digging across the lower Mississippi Valley and swinging east across the Southeast U.S. Sunday with a powerful 150 kt meridonally oriented polar jet aligned just ahead of it. Strong DCVA ahead of the trough coupled with a region of strong warm air advection aided by a 45-55 kt low- level jet will support a broad corridor of intense, deep-layered forcing across much of the Southeast U.S., crossing the local area Sunday afternoon into Sunday evening. While this feature will support a region of widespread rainfall within a well- defined pre-frontal warm sector, it remains unclear if one solid area of rain will spread west-east across the region or if a series of convective bands will prevail. Guidance is essentially mixed on this potential. Either way, it does appear there is a high probability for measurable rainfall impacting the area as moisture steadily increases (PWATs (Precipitable Waters) rising >1.50" by Sunday evening just ahead of the front). High-end categorical probability of precipitation were maintained given these trends. Rain will gradually end from west-east Sunday night as the front clears the coast although some rain will linger for a few hours after FROPA given the front's expected anafrontal structure. Highs will warm into the lower-mid 70s during the day with lows dropping into mid 30s across far interior Southeast Georgia to the mid-upper 40s at the coast Monday morning within a strong post- frontal cold air advection regime.
Widespread cloud cover and rain will tend to temper warm sector instability (average MLCAPE <500 J/kg and Lifted Indices of -1 to -3C). The degree of forcing still looks sufficient for a few thunderstorms. some of which could be strong given the degree of forcing and 0-6km bulk shear noted. This setup is typical of a high shear/low CAPE (HSLC) scenario. While there is a non-zero risk for a localized damaging wind report or two, the overall risk for severe weather looks fairly low at this time. The risk may increase a bit if more instability is realized, so this will be watched carefully.
Breezy to windy conditions will be possible Sunday afternoon into Sunday night as a pre-frontal low-level jet moves over the area and is quickly followed by a strong post-frontal cold air advection. 925 hPa winds are forecast to increase to as high as 45-50 kt by late Sunday afternoon/early evening as the cold front approaches. Some of these winds may be realized to the surface, especially in gusts as temperatures rise through the afternoon. BUFKIT mixed wind profiles show as much as 40 kt of wind at the top of the mixed-layer. Expect gusts 30-35 mph to be rather frequent with a few gusts near 40 mph, especially over the coastal counties where the warmest temperatures will be realized prior to FROPA. Winds could be higher over the elevated bridges across the Charleston and Savannah Metro Areas a well as the bridges heading out to the various barrier islands. These winds could pose a hazard to high-profile vehicles. A Lake Wind Advisory will likely be needed for Lake Moultrie, although winds speeds may be subdued somewhat over the open lake waters by the poor mixing profiles with water temperatures in the upper 50s. There is a chance that a Wind Advisory could be needed for some areas for winds 20-30 mph with gusts approaching 40 mph, especially over the coastal counties.
Long Term - Monday Night Through Friday
Cool and dry high pressure will prevail for next week. Temperatures will gradually climb through the week as the airmass slowly modifies.
Tonight: Very quiet marine conditions will continue across the local waters. Southerly winds should remain in the 5-10 knot range, with seas around 2 feet through the night.
Saturday through Wednesday: The biggest marine impacts will occur Sunday into Monday morning as a cold front approaches then pushes offshore. Strong low-level jetting will help increase winds and build seas ahead of the front Sunday with winds reaching 15-20 kt with gusts to 25 kt across the nearshore legs and Charleston Harbor with winds 20-25 kt with gusts to 30 kt over the Georgia offshore zone and the outer portions of the South Santee-Edisto Beach nearshore zone. The a risk for gales will occur just ahead and immediately behind the front Sunday evening as the most intense portion of the pre-frontal low-level jet pushes through followed by strong post-frontal cold air advection. Gales, at least in frequent gusts, will be most likely occur in the cold air advection regime due to more favorable mixing profiles. Nearshore winds will peak 25- 30 kt with gusts to 35 kt with 30 kt with gusts to 40 kt beyond 20 NM. Seas will peak 4-7 ft nearshore legs with 7-9 ft beyond 20 NM. A mixture of Small Craft Advisories and Gale Watches will be needed in later forecast cycles. Conditions will improve Monday as cold air advection wanes and high pressure builds in. Winds and seas will begin to build again Wednesday as the pressure gradient tightens over the waters. Another round of Small Craft Advisories may be needed.
NOAA Charleston SC Office: Watches - Warnings - Advisories