Charleston Harbor Marine Forecast
|Overnight...Ne Winds 15 Kt.|
|Tue...N Winds 15 To 20 Kt. Waves 1 To 2 Ft.|
|Tue Night...N Winds 15 To 20 Kt With Gusts To 25 Kt. Waves 1 To 2 Ft.|
|Wed...N Winds 15 Kt With Gusts To 20 Kt.|
|Wed Night...Ne Winds 10 To 15 Kt.|
|Thu...Ne Winds 10 Kt.|
|Thu Night...Ne Winds 5 To 10 Kt. A Chance Of Showers.|
|Fri...E Winds 5 To 10 Kt. A Chance Of Showers.|
|Fri Night...S Winds 5 To 10 Kt. Showers Likely.|
|Sat...W Winds 10 Kt. A Slight Chance Of Showers.|
|Sat Night...W Winds 10 Kt. Unless Otherwise Noted, Waves 1 Foot Or Less. Charleston Harbor Water Temperature 58 Degrees.|
Area Forecast Discussion|
National Weather Service Charleston SC
1107pm EST Monday Jan 20 2020
High pressure will build across the area through midweek, then weaken late week in advance of a low pressure system impacting the region this weekend. High pressure will then return late weekend and persist into early next week.
Near Term - Until 6am Tuesday Morning
The max temps for Monday at North Charleston and in downtown Charleston were the coldest they have been since last January. Savannah had it's coldest max temp since November 2019.
Meanwhile, our forecast of the low temperature for downtown Charleston tonight to 28 degrees, which will be the first time that freezing temperatures have been observed since 1/18/2018. In addition, the forecast lows for North Charleston and Savannah will be the coldest temperatures since 1/19/2018.
Conditions still appear too marginal for a Wind Chill Advisory for Charleston and Tidal Berkeley late tonight into Tuesday morning. While there will be some wind chills down near 15 degrees, the coverage is and duration is not enough to warrant the advisory.
Instead we issued a Special Weather Statement, not just for those two areas, but for all counties, as wind chills will be down in the mid and upper teens across many areas from 5-9 am.
In addition, temps tonight into Tuesday morning will be 32F or colder for about 7-12 hours across a good chunk of the forecast area.
Short Term - 6am Tuesday Morning Through Thursday
Chilly high pressure will remain the dominant feature at the surface through Thursday. Aloft, a strong mid level low will swing off the Southeast coast on Tuesday, with heigheights gradually rising in its wake. Deep dry air will preclude any rain, so the most notable feature of the short term will be the temperatures.
The coldest day of the set will be Tuesday when highs only reach the low to mid 40s, then temperatures will slowly moderate through Thursday (although each day will still be below normal). Lows Tuesday night are forecast to range from the mid 20s inland to around freezing at the immediate coast. There will be a decent amount of wind present with an enhanced pressure gradient, so this will make it feel like the upper teens. These values remain shy of Wind Chill Advisory criteria. Wednesday night lows will drop to the 30s.
Lake Winds: Cold air moving over the warmer lake waters Tuesday night into Wednesday will promote favorable mixing profiles. North winds could gust to near 25 knots, and a Lake Wind Advisory could be needed.
Long Term - Thursday Night Through Monday
A coastal trough should linger near the Southeast Coast Thursday night into Friday before lifting north and dissipating in advance of a low pressure system approaching from the west. A cold front associated with this system is anticipated to track across the area Friday night into early Saturday, producing scattered to numerous showers for most locations when moisture is deepest and forcing is strongest. Dry high pressure will then build across the area late weekend and become centered across the Southeast early next week.
In regards to temps, conditions will remain mild ahead of the cold front this weekend, with afternoon highs ranging in the mid/upper 60s Friday and lows ranging in the upper 40s to lower 50s Friday night. Temps will be a degree or two cooler on Saturday with frontal passage ongoing, then remain around 60 degrees for highs Sunday and Monday afternoons and in the upper 30s/lower 40s Sunday and Monday nights.
The marine area will remain between organizing low pressure over the western Atlantic and high pressure centered over the mid-Mississippi River valley. The pressure gradient across the waters should support steady N and NE winds between 15 to 20 kts, a little less in Charleston Harbor. Winds will be a little stronger across the outer GA waters, AMZ374, supporting gusts to 25 kts. Seas are forecast to range from 3 to 4 ft across the nearshore waters to 5 to 6 ft across the outer GA waters. A Small Craft Advisory will remain in effect for AMZ374.
Tuesday through Saturday: North winds will strengthen on Tuesday as the pressure gradient tightens between high pressure inland and developing low pressure offshore. Small Craft Advisories will go into effect for all waters in the morning. There is currently no advisory for the Charleston Harbor in effect, but it will most likely need one at some point later in the day. The worst conditions are forecast to occur Tuesday night into Wednesday, and we have hoisted Gale Watches for the Charleston County nearshore waters and outer Georgia waters. Some improvement is expected Wednesday night into Thursday, but conditions will still be supportive of Small Craft Advisories through Thursday. Winds and seas will then continue to improve Thursday night into Friday as winds turn more onshore in association with a coastal trough along the Southeast Coast. By Friday night, southerly flow returns across all waters in advance of a low pressure system advancing toward the coast from the west. A cold front is expected to shift offshore Saturday, before high pressure builds across the waters late. Conditions will become elevated post frontal passage. but should remain below Small Craft Advisory levels across all waters.
Tides / Coastal Flooding
Cold high pressure will build across the area mid-week while low pressure deepens offshore. Strong north-northeast winds between these two features will help produce elevated tide levels a few days before the upcoming new moon (Jan 24). Tide levels could reach 7.0-7.3 FT MLLW along the Southeast South Carolina coast during the Wednesday and Thursday morning high tides and a Coastal Flood Advisory could eventually be needed.
NOAA Charleston SC Office: Watches - Warnings - Advisories
Small Craft Advisory from 10am Tuesday to 7pm EST Thursday for AMZ352-354. Gale Watch from Tuesday afternoon through Wednesday afternoon for AMZ374. Small Craft Advisory until 4pm EST Tuesday for AMZ374. Gale Watch from Tuesday evening through Wednesday afternoon for AMZ350. Small Craft Advisory from 7am to 7pm EST Tuesday for AMZ350.