Marine Weather Net

South Santee River to Edisto Beach, SC Marine Forecast


TONIGHT

W
WINDS
20 - 25
KNOTS

TUE

N
WINDS
20 - 25
KNOTS

TUE NIGHT

W
WINDS
15 - 20
KNOTS

WED

W
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
AMZ350 Forecast Issued: 955 PM EDT Mon Mar 18 2024

GALE WARNING IN EFFECT UNTIL 9 AM EDT TUESDAY
Tonight...W Winds 20 To 25 Kt, Becoming Nw 25 To 30 Kt With Gusts To 40 Kt Late This Evening. Seas 3 To 4 Ft, Building To 4 To 5 Ft After Midnight.
Tue...N Winds 20 To 25 Kt, Becoming Nw 5 To 10 Kt In The Afternoon. Seas 3 To 4 Ft, Subsiding To 2 To 3 Ft In The Afternoon.
Tue Night...W Winds 15 To 20 Kt With Gusts To 25 Kt. Seas 2 To 3 Ft, Building To 3 To 4 Ft After Midnight.
Wed...W Winds 15 To 20 Kt With Gusts To 25 Kt. Seas 3 To 4 Ft.
Wed Night...Sw Winds 15 Kt, Becoming W After Midnight. Seas 3 To 4 Ft.
Thu...N Winds 10 To 15 Kt, Becoming Ne In The Afternoon. Seas 2 To 3 Ft.
Thu Night...E Winds 10 To 15 Kt. Seas 3 Ft. A Chance Of Showers After Midnight.
Fri...E Winds 15 Kt. Seas 4 To 6 Ft. Showers With A Slight Chance Of Tstms.
Fri Night...Ne Winds 15 Kt. Seas 6 To 8 Ft. Showers Likely With A Slight Chance Of Tstms.
Sat...N Winds 15 To 20 Kt. Seas 6 To 8 Ft. A Chance Of Showers.
Sat Night...N Winds 15 To 20 Kt. Seas 5 To 7 Ft. A Slight Chance Of Showers. Winds And Seas Higher In And Near Tstms.
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Area Forecast Discussion
National Weather Service Charleston SC
1018pm EDT Monday Mar 18 2024

Synopsis
High pressure will build over the area tonight and prevail into Thursday. A storm system could impact the area Friday and Saturday, before high pressure returns early next week.

Near Term - Through Tuesday
Tonight: A short-wave trough will be swinging through the Carolinas and Mid Atlantic region during the course of the night, passing offshore well before daybreak. No more than some altocumulus will occur with the passage of that trough, especially north of I-16 in South Carolina. There will also be few-scattered cirrus early on in response to the right entrance region of a 140+ upper jet.

The main issue for us will be a period of gustier winds and decent cold advection as a large of high pressure centered in the vicinity of the Arklatex expands into the Gulf Coast and southeast states in the wake of the trough. Tightening pressure gradient (4-5 millibars across the area for a few hours late evening and the first part of the overnight) will lead to a period of gustier winds during that time, with gusts of 25 to 30 mph anticipated across the region. As a result, a Lake Wind Advisory remains in effect for Lake Moultrie. Winds will be tapering off some through the overnight hours as cold advection slows down.

Temperature-wise: Strong cold advection drives the 850 mb temps down into the -2C to -4C range by morning. This is far below normal, which should be around 8.5C to 8.7C. Along with diminishing winds and clearing skies, lows will drop through the 30s for all areas away from the coast with the coldest readings well inland. Associated wind chills will be as low as in the 20s far inland late. Persistent winds and dry incoming air mass will limit frost development to no more than maybe a little patchy coverage late near the US-301 corridor, but only if RH levels are high enough.

Short Term - Tuesday Night Through Thursday
Aloft, a large trough will pivot offshore Tuesday, shifting further away from the region while a zonal flow takes place across the Southeast United States through mid-week. At the sfc, high pressure across the South-central United States will extend east across Gulf Coast states and Carolinas Tuesday into Wednesday, before a cold front arrives from the north/northwest by early Thursday.

Conditions will remain dry locally through the middle of the week while a west-northwest downslope wind prevails along the eastern edge of the high centered to our west, even as the cold front pushes into the local area by early Thursday. Despite ample surface heating under clear skies, temps will struggle to warm significantly on Tuesday while weak cold air advection wanes across the region. In general, high temps should only peak in the upper 50s to lower 60s (warmest across southeast Georgia). Although temps are cooler during peak heating, dry air should lead to afternoon RH values between 20- 25% away from the coast Tuesday afternoon. Surface winds are expected to remain below 10 mph though, so fire weather concerns should be limited.

Surface winds should slowly turn southwest Tuesday night into Wednesday, offsetting some radiational cooling at night and resulting in airmass modification on Wednesday ahead of an arriving cold front. In general, Tuesday night lows should dip into the upper 30s/lower 40s inland to mid-upper 40s near the coast. On Wednesday, high temps should peak in the lower 70s with sunny conditions in place. Guidance indicates a dry cold front pushing across the region Wednesday night, likely becoming positioned along or just south of the local area by daybreak Thursday. Despite northerly winds post fropa, surface temps should peak in the lower 70s under partly sunny skies in advance of a low pressure system developing and shifting eastward across the northern Gulf of Mexico heading into late week.

Long Term - Thursday Night Through Monday
The weather becomes more active as we head into late week, although still some forecast details to hash out. An upper wave is expected to pass across the Southeast United States early Friday through early Saturday, forcing an area of low pressure across the northeast Gulf to possibly strengthen while tracking over/near the Georgia and South Carolina coasts. PWATs (Precipitable Waters) should increase to around 1.25 inches as the system nears, and with strong isentropic ascent and a lingering front across the area, should promote showers to develop locally Thursday night into Friday morning. Scattered to numerous showers are now forecast to occur for most areas Friday and Friday evening, before precipitation activity trends offshore with the surface low pulling away Saturday. Some guidance suggests some modest instability developing near the coast and offshore as the low tracks near the region, so a few embedded thunderstorms are possible along the immediate coast.

The aforementioned low should continue to depart the region late weekend as high pressure builds inland. Aside from some lingering showers Saturday morning into early afternoon, precipitation chances should become confined to the coastal waters by Saturday evening. Dry conditions should then prevail Sunday with high pressure in place.

Marine
Tonight: A strong 1027 mb high centered near the Arklatex will expand east and stretch over the coastal waters. A tight gradient, with as much as a 3 or 4 mb spread, plus constant isallobaric pressure climbs will exist. Those conditions along with significant cold air advection will allow for good mixing of the 35 or 40 kt geostrophic winds. As a result we have Gale Warnings in effect for all Atlantic waters, with a high end Small Craft Advisory in Charleston Harbor. Seas will be limited close to shore due to the offshore fetch with NW winds. But as one navigates further into the Atlantic, seas will be as high as 5 feet near 20 nm out, and up to 8 feet beyond 40 or 50 nm out.

Tuesday through Saturday: Marine conditions will improve on Tuesday, although there will be another brief wind surge Tuesday night with gusts to near advisory criteria, especially over the Charleston County waters. A somewhat enhanced pressure gradient could support elevated winds through late week, but conditions should remain just below Small Craft Advisory levels through Thursday. An area of low pressure is then expected to pass near/off the Southeast Coast Friday into Saturday, likely contributing to deteriorating marine conditions across local waters this weekend. Small Craft Advisories should be needed across most waters, but the track/strength of the low pressure system will play a large role in overall impacts along the Southeast Coast.

NOAA Charleston SC Office: Watches - Warnings - Advisories
GA...None. SC...Lake Wind Advisory until 8am EDT Tuesday for SCZ045.

Marine
Small Craft Advisory until 6am EDT Tuesday for AMZ330. Gale Warning until 9am EDT Tuesday for AMZ350-352-354-374.