Charleston Harbor Marine Forecast
|Tonight...E Winds 5 To 10 Kt, Becoming Ne Winds 10 Kt. A Chance Of Showers This Evening.|
|Mon...Ne Winds 5 To 10 Kt.|
|Mon Night...Ne Winds 5 To 10 Kt.|
|Tue...Ne Winds 5 Kt. A Slight Chance Of Showers In The Afternoon.|
|Tue Night...E Winds 5 Kt. A Slight Chance Of Showers.|
|Wed...Ne Winds 5 To 10 Kt, Becoming E In The Afternoon. A Slight Chance Of Showers.|
|Wed Night...S Winds 5 To 10 Kt. A Chance Of Showers.|
|Thu...S Winds 15 To 20 Kt. Waves 1 To 2 Ft. A Chance Of Showers With A Slight Chance Of Tstms.|
|Thu Night...Sw Winds 15 Kt. A Chance Of Showers.|
|Fri...Nw Winds 15 Kt. A Slight Chance Of Showers.|
|Fri Night...N Winds 15 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 75 Degrees.|
| Area Forecast Discussion|
National Weather Service Charleston SC
154pm EDT Sunday Oct 25 2020
An upper disturbance will move through today, followed by a weak cold front tonight. Weak high pressure is expected to prevail through the middle of the week. A storm system is expected to bring impacts to the region late in the week.
Near Term - Through Tonight
This Afternoon: A mid-upper level low depicted on water vapor imagery will slowly traverse east across Georgia and South Carolina this afternoon and evening while a surface cold front gradually shifts to the coast. Latest visible satellite imagery along with surface observations indicate the front making way across Southeast Georgia, spawning few to scattered showers mainly along the I-95 corridor in Southeast Georgia early this afternoon. Expect additional showers to develop north into Southeast South Carolina during the afternoon, a few of which could become thunderstorms as MLCAPE approaches 1000 J/kg during peak heating. Any thunderstorm will likely remain short-lived given deepest moisture remaining offshore. Cooler high pressure is then anticipated to spread across the region from the north behind the departing front heading into evening hours, putting an end to any thunderstorm and transitioning showers over to a drizzle type setup heading as low-level moisture lingers into early overnight hours. In general, afternoon high temps should range in the upper 70s to around 80 degrees north to low/mid 80s south before the onset of east-northeast surface winds within high pressure take place late afternoon into evening hours.
Tonight: Low pressure should push offshore to the northeast allowing high pressure to build in from the north. A few showers and/or drizzle could occur around the Charleston area early, then predominately remain drizzle through the evening and early overnight period as stratus clouds develop/lower, especially for areas closer to the Pee Dee/Midlands. Some fog is also likely, especially in Georgia where low-level winds will be weakest. Low temperatures will continue to be above normal, mostly mid to upper 60s.
Short Term - Monday Through Wednesday
Monday: The mid-levels will consist of southwest flow and rising heigheights overhead as broad high pressure develops and then strengthens over FL. At the surface, high pressure will be to our north during the day, with the center of the high shifting towards the Outer Banks of N.C. overnight. Meanwhile, a weak coastal trough should prevail to our southeast. Models indicate there might be some light showers associated with the coastal trough. However, they are expected to remain over the coastal waters because dry air associated with the high will be dominant over land areas. Temperatures may be somewhat tricky during the day. If low clouds prevail most of the day, then highs may struggle to reach the mid 70s, especially in northeast flow. But if there's more sun than clouds, then mid- level temperatures and thickness values support highs making a run for 80 degrees in most locations. We leaned more towards the second solution, especially across our coastal GA counties. Temperatures at night will remain nearly 10 degrees above normal.
Tuesday: Generally southwest flow in the mid-levels should persist as broad high pressure initially over FL shifts off the Southeast coast. Surface high pressure near the Outer Banks of N.C. in the morning will move offshore while a weak coastal trough prevails to our southeast. Additionally, a storm will be developing while it moves through the central Gulf of Mexico. The synoptic flow will lead to Gulf and Atlantic moisture increasing, with PWATs (Precipitable Waters) expected to exceed 1.5" across portions of our area overnight. The general consensus of the models is to paint an area of light showers generally south of I-16 during the afternoon. We have chance POPs there and lower POPs elsewhere. But if the drier air holds in place longer, then these POPs will need to be lowered. Overnight, we generally have slight chance POPs since most of the showers should prevail over the coastal waters. Temperatures will continue to be well above normal.
Wednesday: The mid-levels will consist of southwest flow as broad high pressure off the Southeast coast moves away and a strong trough approaches from the west. At the surface, a storm in the Gulf should combine with another storm system in the lower MS Valley. Moisture continues to creep upwards with time. However, the lift across our area is limited and varies. The result is each models paints a different picture with the days rainfall potential. We generally kept the highest POPs over our GA counties (where the highest moisture is), tapering into our SC counties. But we expect more changes will be needed to all aspects of the forecast as models come into better agreement. Temperatures will continue to be well above normal.
Long Term - Wednesday Night Through Sunday
Mid-level high pressure located offshore will move away on Thursday. Meanwhile, a strong trough will approach from the west on Thursday, then pass overhead or just to our north on Friday. Zonal flow is expected on Saturday. At the surface, a storm system will cross through our region Thursday into Thursday night, bringing rainfall. Conditions dry out Friday as high pressure builds in from the west, and remain dry into Saturday. Temperatures will be colder behind the front.
This Afternoon and Tonight: A weak cold front will shift offshore late this afternoon, followed by high pressure building across the area from the north overnight. The setup will favor east-southeast winds around 10 kts or less for much of the day, before turning more northeast tonight with speeds increasing to 10-15 kt late and heading into daybreak. Seas will be no higher than 2-3 ft across nearshore waters and no higher than 4-5 ft across offshore Georgia waters while long period swell associated with Tropical Cyclone Epsilon subsides across local waters.
Extended Marine: Weak high pressure should prevail to our north through Tuesday, then shift offshore on Wednesday. Winds and seas will remain below Small Craft Advisory levels during that time period. Late Wednesday a developing storm system will approach from the west, moving across the region on Thursday. Conditions across the coastal waters will depend on the strength and evolution of the storm. Small Craft Advisories may be needed for most of the waters late in the forecast period.
Long period swells from distant Tropical Cyclone Epsilon will continue to diminish today but still be enough to cause an elevated risk of rips along the southern SC/northern GA coasts.
NOAA Charleston SC Office: Watches - Warnings - Advisories
GA...None. SC...None. MARINE...None.