Marine Weather Net

Charleston Harbor Marine Forecast


10 - 15


10 - 15


10 - 15


5 - 10

The Marine Weather Forecast In Detail:
AMZ330 Forecast Issued: 1234 AM EDT Sun Mar 29 2020

Rest Of Tonight...Sw Winds 10 To 15 Kt.
Sun...Sw Winds 10 To 15 Kt.
Sun Night...Sw Winds 10 To 15 Kt With Gusts To 20 Kt, Becoming W 5 To 10 Kt After Midnight.
Mon...W Winds 5 To 10 Kt.
Mon Night...Sw Winds 5 To 10 Kt, Becoming Nw After Midnight.
Tue...Ne Winds 5 To 10 Kt, Becoming Se In The Afternoon. A Chance Of Showers In The Morning, Then Showers Likely With A Chance Of Tstms In The Afternoon.
Tue Night...Sw Winds 10 Kt, Becoming W After Midnight. A Chance Of Tstms. Showers.
Wed...Nw Winds 10 To 15 Kt. A Chance Of Showers.
Wed Night...N Winds 10 Kt.
Thu...Nw Winds 5 To 10 Kt.
Thu Night...W Winds 5 Kt. Mariners Are Reminded That Winds And Waves Higher In And Near Tstms. Unless Otherwise Noted, Waves 1 Foot Or Less. Charleston Harbor Water Temperature 68 Degrees.
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Area Forecast Discussion
National Weather Service Charleston SC
1238am EDT Sunday Mar 29 2020

Very warm high pressure will prevail through Sunday. A dry cold front will push through Sunday night, followed by high pressure Monday. Low pressure will then cross the area Tuesday into Tuesday night, followed by high pressure through late week.

Near Term - Until 6am This Morning
Satellite imagery shows a tad more clouds floating over our area, especially the Charleston Tri-County, so we nudged the sky cover up. Also, placed the latest temperature and dew points observations into the hourly grids and blended for the next few hours. Everything else is on track.

As the mid and upper ridge slips a bit further east overnight, it will allow for at least scattered cirrus clouds to continue moving through. At the surface, high pressure will be the main feature, and with enough mixing around the high and between an upstream cold front, this will keep our potential for fog quite low. Maybe some sea fog, if it's able to form will skirt the barrier islands from Tybee northward after 3 or 4 am. But chances are low enough to not add to the forecast. Also, low stratus will either form and/or advect into our far west- southwest counties closer to sunrise. On average, skies will be mostly clear or partly cloudy.

Given a deep southwesterly flow and elevated dew points, temps tonight will struggle to fall to the lower and middle 60s. Compare that with normal lows that are mainly in the upper 40s and lower 50s, and it'll be a warm night for late March. It'll be close to record high mins for downtown Charleston, which is 68F for both March 28 and March 29.

.SHORT TERM /6am THIS MORNING THROUGH TUESDAY/... Sunday: Ahead of an approaching cold front, deep-layered high pressure will produce another unseasonably warm day featuring record/near record highs in the upper 80s to lower 90s away from the beaches.

Sunday night: A cold front will cross the region. While this front should initially support showers/thunderstorms west of the region Sunday afternoon into Sunday evening, models agree that capping/subsidence produced by the high pressure will dominate over our region, and any upstream convection will dissipate before reaching our area. Thus, the cold front will pass with clouds, a wind shift to the north and advection of drier air/lower dewpoints into the region.

Monday: Weak high pressure will build over the region, and even though temperatures will be somewhat cooler than those of this weekend, highs will still average well-above normal for late March, in the lower/middle 80s at many locations away from the immediate coast, and even in the upper 80s across parts of interior SE GA south of I-16. On the beaches, offshore winds to start will allow temperatures to recover well into the 70s/around 80F. Then, the afternoon sea breeze should drop temperatures at least back into the lower 70s most locations.

Monday night: Clouds should increase/thicken ahead of low pressure developing west of the region. However, rain is not expected. Temperatures should bottom out in the upper 50s to lower 60s inland, and in the lower/middle 60s at the coast.

Tuesday: Low pressure will approach the region during the morning and will track east across the area Tuesday afternoon. In response to intensifying low/mid level moisture transport and increasing deep layered forcing for ascent, precipitation coverage should ramp up as the day progresses. The latest forecasts depicts slight chance/chance PoPS Tuesday morning increasing to likely/categorical most areas Tuesday afternoon. The latest forecast also indicates most of the region breaking into the warm sector with highs ranging from the lower/middle 70s north to the lower/middle 80s south. However, temperature forecasts remain highly uncertain and depend on the exact track of the surface low. Temperatures across northern/inland counties could struggle to climb out of the 60s if precipitation supports an in-situ wedge.

Most importantly, the low pressure will produce the potential for severe weather Tuesday, especially during the afternoon/evening. At one extreme of the solution spectrum, the warm sector could surge into most/all of the forecast area, and the resulting instability could combine with strong/cyclonic shear to support a severe weather event. At the other extreme, greater coverage of precipitation and a more expansive/persistent in-situ wedge could greatly limit the potential for any severe weather. Forecasts mention a chance for thunderstorms Tuesday afternoon/evening, and we will include a brief mention of the potential for severe weather within the Hazardous Weather Outlook. However, critical details remain highly uncertain, so expect this forecast to evolve over the next couple of days.

Long Term - Tuesday Night Through Saturday
Low pressure will shift off the coast Tuesday night and continue to lift away from the area on Wednesday. A few showers could linger into Wednesday, but largely the bulk of precipitation will end Tuesday night. High pressure will then build into the area allowing for dry weather through Thursday. Models beyond this time aren't in the best agreement, although it appears another front and/or low could pass through late week. Temperatures will be more seasonable.

Overnight: An Atlantic ridge that extends across Florida will actually strengthen a bit between now and dawn, as an upstream cold front stretches from the lower Great Lakes to the lower Mississippi Valley. There will remain enough of a gradient between these two features to produce S-SW winds as high as 12-18 kt, with seas 2-4 ft.

Elevated winds across the waters are keeping sea fog from forming. Though, given the high dew points over the waters, we're maintaining the mention of patchy fog.

Until the initial cold front advances through the waters Sunday night, patchy fog could develop over the nearshore waters. However, the chance for widespread/significant sea fog remains low Sunday and Sunday night.

Expect elevated SW winds as high as 15-20 knots and seas 3-5 feet Sunday into Sunday evening. Then, a dry cold front will cross the waters later Sunday night, and winds will shift to the northwest at 5-10 knots. High pressure will shift over the waters Monday, and the associated weak pressure gradient will promote widespread sea breeze development Monday afternoon. Monday night, under the high pressure variable winds less than 10 kt will prevail. Also, seas will settle back to 2-3 ft Monday and 1-2 ft Monday night. Low pressure will then approach the waters Tuesday and will track over marine zones Tuesday evening. As a result, winds will increase, initially from the east/southeast early Tuesday, veering to the south Tuesday afternoon then to the southwest Tuesday evening. Depending on the track/strength of the low, Small Craft Advisory conditions are possible any time Tuesday afternoon into Tuesday evening, but the probability remains insufficient to justify an Advisory within the saturday afternoon package. Then, as the low pressure intensifies and tracks northeast off the NC coast, a cold front will push through the region, northwest winds will surge into the waters and seas will build. Given the tightening pressure gradient on the southwestern periphery of the Atlantic low/in the wake of the cold front, the probability for Small Craft Advisory conditions will increase significantly. This regime will then persist through Wednesday night, followed by somewhat lighter offshore winds/seas Thursday through Friday.

Record high maximum and high minimum temperatures Sunday.

KCHS: Sunday 3/29: 87 (2012) / 67 (1997)

KSAV: Sunday 3/29: 90 (1907) / 67 (1991)

KCXM: Sunday 3/29: 91 (1907) / 68 (1997)

NOAA Charleston SC Office: Watches - Warnings - Advisories
GA...None. SC...None. MARINE...None.