Charleston Harbor Marine Forecast
|Tonight...Sw Winds 15 To 20 Kt With Gusts To 25 Kt, Diminishing To 10 Kt Late. Waves 1 To 2 Ft This Evening. A Slight Chance Of Showers After Midnight.|
|Thu...Sw Winds 10 To 15 Kt. A Chance Of Showers.|
|Thu Night...W Winds 10 Kt, Becoming Nw After Midnight. A Chance Of Showers In The Evening.|
|Fri...Ne Winds 10 Kt, Becoming E In The Afternoon.|
|Fri Night...Variable Winds 5 Kt. A Chance Of Showers After Midnight.|
|Sat...Se Winds 5 Kt. A Slight Chance Of Tstms. Showers Likely.|
|Sat Night...S Winds 5 To 10 Kt, Becoming W After Midnight. Showers Likely With A Slight Chance Of Tstms In The Evening, Then A Chance Of Showers After Midnight.|
|Sun...W Winds 5 To 10 Kt. A Chance Of Showers.|
|Sun Night...Sw Winds 10 Kt. A Slight Chance Of Showers.|
|Mon...W Winds 10 Kt. A Slight Chance Of Showers.|
|Mon Night...Nw Winds 10 Kt. A Slight Chance Of Showers. 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.|
| Area Forecast Discussion|
National Weather Service Charleston SC
844pm EDT Wednesday April 14 2021
A cold front will advance through the region Thursday and then stall off the Southeast coast Friday through early next week. A series of low pressures will track along this stationary front into early next week.
Near Term - Until 6am Thursday Morning
Reflectivity data from KCLX and KJAX show a line of showers approaching the far Southeast Georgia coast from roughly Darien south to Cumberland Island. It appears rainfall rates are high enough with this line to punch through the large, dry sub-cloud layer noted on both the KCHS and KJAX 15/00z raobs. Mesonet observations in the vicinity of the line show rainfall amounts of a only a few hundredths with a few spots surpassing a tenth of an inch. probability of precipitation have been increased to 40% for Inland and Coastal McIntosh County and the adjacent coastal waters through late evening. The rest of the forecast is unchanged.
Overnight a lee-side trough will move steadily east and offshore early Thursday morning. A few showers could develop late as low-level jetting intensifies ahead of this feature, but moisture levels below the sub-cloud layer (cloud bases lowering to 7000-9000 ft late) still look too dry to support anything measurable. Slight chance probability of precipitation around 20% were maintained across the west and northern zones where a hundredth could be eked out, but confidence is this is quite low. Rain chances will increase closer to daybreak across mainly the interior Southeast Georgia zones as deeper moisture and higher PWATs (Precipitable Waters) begin to advect northeast ahead of an approaching cold front. Lows will range from the lower 60s inland to 66-68 at the beaches and Downtown Charleston.
Short Term - 6am Thursday Morning Through Saturday
Thursday: A cold front will move through the region Thursday afternoon. Models are in decent agreement, with showers mainly focused in the southern counties of the forecast area. There is also a chance of thunder in the far southern zones. However, there is a chance for convection to form in northern Florida, which would inhibit moisture transport to our forecast area and limit rain chances. Have kept most POPs in the 30-40% range, however confidence is low with regards to how widespread the showers will be across the region.
Thursday Night through Friday Night: Post frontal passage cloudy conditions will persist along with cooler temperatures. Lows Thursday and Friday night in the mid 50s and highs Friday in the low 70s.
Saturday: Models are in agreement and depicting a rather wet day for Saturday. Model soundings are showing PWAT (Precipitable Water) values upwards of 1.6 inches, which is above the 90th percentile for this time of year. There is also the potential for elevated convection and have a slight chance of thunderstorms across the entire area. Have kept POPs likely, because there is not enough certainty this far out to go any higher, however, these may become categorical in the next few forecast issuances.
Long Term - Saturday Night Through Wednesday
Unsettled conditions with at least isolated/scattered showers will persist into Tuesday as additional waves of low pressure track near the Southeast coast. Details regarding timing, coverage and intensity of precipitation remains uncertain. High pressure should finally expend into the region with drier conditions by the middle of next week. Highs in the 70s and lows in the 50s should remain common. However, greater coverage of showers could result in cooler daytime temperatures Sunday, Monday or Tuesday.
Tonight: Winds are expected to increase across the waters as low-level jetting strengthens ahead of a lee-side through. The gust potential to 25 kt looks high enough to expand the Small Craft Advisory to all nearshore waters through 06z. The Charleston Harbor will be influences by the decaying sea breeze, but could also see some impact from low-level jetting. The advisory was maintained there as a result. The combination of gusty winds and seas building to 6 ft will keep the advisory going for the Georgia offshore waters through 09z.
Thursday through Monday: Thursday, ahead of a cold front, southwest winds 15 to 20 knots and seas 2 to 4 are expected. A gust or two to 25 knots cannot be ruled out. After frontal passage winds will shift to the west/northwest Thursday evening at 10 to 15 knots, before shifting again to the north/northeast early Friday morning at 10 to 15 knots. Seas will average 2 to 4 feet. There is a chance for showers and/or thunderstorms Thursday, especially in the GA waters. Then again there is a chance for showers and/or thunderstorms on Saturday across all the waters.
NOAA Charleston SC Office: Watches - Warnings - Advisories
Small Craft Advisory until 11pm EDT this evening for AMZ330. Small Craft Advisory until 2am EDT Thursday for AMZ350-352- 354. Small Craft Advisory until 5am EDT Thursday for AMZ374.