Charleston Harbor Marine Forecast
| Rest Of Today...Sw Winds 10 To 15 Kt, Increasing To 15 To 20 Kt In The Afternoon. |
| Tonight...Sw Winds 10 To 15 Kt With Gusts To 20 Kt. |
| Thu...Sw Winds 10 Kt, Increasing To 15 To 20 Kt With Gusts To 25 Kt In The Afternoon. Waves 1 To 2 Ft. A Slight Chance Of Showers And Tstms In The Afternoon. |
| Thu Night...Sw Winds 10 To 15 Kt. A Chance Of Showers And Tstms. |
| Fri...W Winds 5 To 10 Kt, Becoming Sw In The Afternoon. A Chance Of Showers And Tstms. |
| Fri Night...Sw Winds 5 To 10 Kt. A Chance Of Showers And Tstms. |
| Sat...S Winds 5 To 10 Kt. A Slight Chance Of Showers And Tstms. |
| Sat Night...S Winds 5 To 10 Kt. |
| Sun...S Winds 5 To 10 Kt. A Slight Chance Of Showers And Tstms. |
| Sun Night...S Winds 5 To 10 Kt. Winds And Waves Higher In And Near Tstms. Unless Otherwise Noted, Waves 1 Foot Or Less. Charleston Harbor Water Temperature 82 Degrees. |
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Area Forecast Discussion National Weather Service Charleston SC 1157am EDT Wednesday Jun 18 2025 Synopsis High pressure in the Atlantic will prevail across the Southeast this week. A cold front could approach, then pass just to our north later this week. Near Term - Through Tonight The region will remain under a large H5 ridge through today and tonight. The surface pattern will feature large high pressure centered over the western Atlantic with a trough over the western Carolinas. This pattern will support southwest through this morning. A sea breeze should develop early this afternoon, drifting inland through the mid to late afternoon hours. As the sea breeze pushes inland, dewpoints may climb into the mid to upper 70s with temperatures in the low to mid 90s, CAPE values should peak between 1500-2000 J/kg. Isolated to scattered showers and thunderstorms should develop near the sea breeze this afternoon. Slow storm motions and greater coverage across SE GA may yield pockets of rainfall in excess of 2 inches. Otherwise, conditions across the forecast area will remain hot with highs in the low to mid 90s. Heat index values across the SC Lowcountry may range between 100-105. Tonight, showers and thunderstorms across the CWA (County Warning Area) should dissipate by mid-evening. The rest of the night is forecast to remain dry and mild. Low temperatures should range from near 80 along the coast to the mid 70s inland. Short Term - Thursday Through Saturday Throughout the day on Thursday, a mid-level shortwave begins to flatten the ridge aloft allowing for additional moisture to be advected in from the west-southwest, bringing PWATs (Precipitable Waters) near the 2 inch mark. At the surface the Atlantic high pressure remains parked to our east-southeast, while to our west a cold front will be moving towards the area along the aforementioned shortwave. This will lead to marginally breezy wind gusting into the 20s, especially behind an afternoon sea-breeze, which will offer some relief from temperatures in the 90s. While we may see some diurnally driven and/or sea-breeze driven convection, additional chances for showers and thunderstorms arrive as the front approaches during the evening and overnight hours. While deep-layer shear remains low at around 20 knots, 1500- 2000 J/kg of MUCAPE does bring a risk for severe thunderstorms. Long and skinny CAPE profiles would suggest strong wind gusts to 60 mph being the main threat with DCAPE values of 1000-1500 J/kg. The long and skinny CAPE profiles are also indicative of locally heavy rainfall being possible, particularly if any repeat/training storms occur. Storm Prediction Center has areas along and north of I-26 in a level 1 out of 5 risk for severe thunderstorms, which matches well with various AI/ML models that forecast severe thunderstorms. What happens with the front as it reaches our area remains uncertain, as some models have it quickly falling apart and/or becoming stationary, while others bring it through the area overnight into Friday. As this will be the main driver of our weather, confidence decreases given the multitude of scenarios that could play out. Deterministic models and ensembles do point towards chances for showers and thunderstorms decreasing overnight and into the morning hours, and increasing again during the afternoon hours on Friday. Again, depending on the front, 2000 to possibly as much as 3000 J/kg of MUCAPE may be available, though shear values continue to remain on the low side. Chances for severe thunderstorms are uncertain. As has been the case, temperatures in the lower to mid 90s are expected to build throughout the morning into the afternoon hours, with heat indices in the 90s to lower 100s. After the trough has finished swinging through, Saturday will see upper level ridging building from the west. This will continue warm/hot temperatures with chances for diurnally driven showers and thunderstorms. trong> The aforementioned upper level ridge continues to build as the center slides towards the northeast and a surface high pressure remains over the Atlantic. Temperatures remain largely in the lower to mid 90s with heat indices topping out 100-105F. Diurnally driven showers and thunderstorms continue into the beginning of next week. Marine Today and tonight, the forecast area will remain between a high centered over the western Atlantic and a lee trough over the western Carolinas. A sea breeze will develop early this afternoon, drifting inland through the rest of the day. This pattern should support SSW winds between 10-15 kts with gusts to 20 kts through the near term period. Seas are forecast to range from 3 to 4 ft. Thursday through Monday: At the surface the Atlantic high pressure remains parked to our east-southeast, while to our west a cold front will be moving towards the area along the aforementioned shortwave. This will lead to marginally breezy wind gusting into the 20s, especially behind the afternoon sea-breeze. The sea-level pressure gradient does look to tighten as the aforementioned front moves towards the area, which may be enough to lead to a Small Craft Advisory for the Charleston Harbor and near-shore marine zones Thursday afternoon into Friday morning. Showers and thunderstorms are expected to move offshore in the afternoon into the overnight hours, with storms possibly carrying a risk for strong winds. Friday through the weekend: Diurnally driven showers and thunderstorms may move offshore each day, with otherwise no marine concerns at this time. NOAA Charleston SC Office: Watches - Warnings - Advisories GA...None. SC...None. Marine None. |
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