Marine Weather Net

Charleston Harbor Marine Forecast


TONIGHT

S
WINDS
10 - 15
KNOTS

THU

SW
WINDS
20 - 25
KNOTS

THU NIGHT

NW
WINDS
5 - 10
KNOTS

FRI

NW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
AMZ330 Forecast Issued: 620 PM EST Wed Jan 23 2019

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY AFTERNOON
Tonight...S Winds 10 To 15 Kt, Increasing To 20 Kt With Gusts To 30 Kt After Midnight. Waves Building 1 To 2 Ft. A Chance Of Showers This Evening, Then Rain With A Slight Chance Of Tstms After Midnight. Rain May Be Heavy At Times After Midnight With Vsby 1 Nm Or Less.
Thu...Sw Winds 20 To 25 Kt With Gusts To 30 Kt, Becoming W 15 Kt With Gusts To 20 Kt In The Afternoon. Waves 2 To 3 Ft In The Morning, Subsiding To 1 To 2 Ft. Rain With A Slight Chance Of Tstms In The Morning. Rain May Be Heavy At Times Early With Vsby 1 Nm Or Less.
Thu Night...Nw Winds 5 To 10 Kt.
Fri...Nw Winds 5 To 10 Kt.
Fri Night...Nw Winds 5 To 10 Kt.
Sat...Nw Winds 5 Kt.
Sat Night...Nw Winds 5 Kt.
Sun...N Winds 5 Kt.
Sun Night...N Winds 5 To 10 Kt.
Mon...Ne Winds 5 To 10 Kt.
Mon Night...N Winds 5 To 10 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 54 Degrees.
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Area Forecast Discussion
National Weather Service Charleston SC
706pm EST Wednesday Jan 23 2019

Synopsis: A strong cold front will sweep through the region late tonight and move offshore Thursday morning. High pressure will then return through the weekend. Another cold front could impact the region by Tuesday.

Near Term - Until 6am Thursday Morning
A band of light showers embedded within a broad region of enhanced surface moisture convergence and weak sentropic assent will move eastern portions of Berkeley County as well as central and upper Charleston County through 9 PM. This area of rain could drop a few hundredths and a few rumbles of thunder can not be completely ruled out with some elevated instability noted just offshore. Otherwise, dry conditions will prevail for much of the evening hours as a cold front approaches from the west.

A large area of moderate to locally heavy rainfall extends from southern Kentucky into the north-central Gulf of Mexico ahead of a strong cold front early this evening. This activity is being supported by a strong southern stream trough digging across eastern Texas and an impressive advection of moisture from off the Gulf of Mexico via a strong pre-frontal low-level jet. The large frontal band will move steadily east across the remainder of the Deep South and into the Southeast U.S. overnight as the supporting upper trough begins to eject northeast and the pre- frontal low-level jet continues to pump deep, gulf moisture, characterized by PWATS in excess of 1.5 inches, into the region. Current data suggest the eastern edge of the rain shield will reach an hour or so after midnight and extend east to the coast prior to daybreak. Pops around 100% look on track.

Guidance shows an impressive coupling of the right entrance region of the upper jet with a region of mid-level instability that is forecast to move out of the northeast Gulf of Mexico and into the local area late. This setup should support a line of strongly forced embedded convection within the larger rain shield with the potential for a few elevated tstms. While severe weather does not appear likely at this time given the lack of meaningful surface-based instability, a few strong, convectively induced wind gusts of 45-55 mph could occur given the impressive wind fields that are in place. These could down an isolated tree or two. Even strong low-level jetting ahead of the rain shield itself could yield wind gusts 30-40 mph at times, especially along the coastal counties. The need for a Wind Advisory can not be completely ruled out.

Temperatures will hold steady and/or slowly rise overnight, then begin to fall across the far west as the cold front enters the forecast area. Lows will range from the upper 50s west of I-95 to the lower 60s at the coast, but these values will occur at various periods through the night.

Lake Winds: A marginal Lake Wind Advisory is in place for Lake Moultrie. Cold lake waters should keep conditions largely below 20 kt, but gusty conditions appears likely around the lakeshore. This will change Thursday morning as cold air advection initiates with the passage of the cold front.

.SHORT TERM /6am THURSDAY MORNING THROUGH SATURDAY/... Thursday and Thursday night: All of the active weather in the short term period will take place Thursday morning as a strong cold front pushes off the coast. Model guidance is in good agreement with the cold front and its line of showers and isolated thunderstorms aligned directly across the middle of the forecast area just after sunrise. The line of showers and embedded isolated thunderstorms will quickly move off the coast and land areas should be completely precipitation free by noon. The window for any strong to marginally severe storms will be only a couple of hours long, primarily for the Charleston Tri-County region. Given the time of day and lack of instability, the threat will be low. However, the background wind field is quite impressive and strong gusty winds are expected along and just ahead of the line. In fact, we could end up needing a Wind Advisory along the coast for a few hours to account for wind gusts up to 40 mph. Overall, the front and general setup looks quite similar to this past Saturday night and Sunday morning. Skies will clear through the afternoon hours and temperatures will hold nearly steady from about mid morning onward. Highs will occur around or just after sunrise ahead of the front with temperatures topping out in the mid 60s. Winds will remain gusty through the afternoon, with westerly winds topping out in the 20-25 mph range. Overnight, clear and cold with lows falling into the low 30s inland to the mid/upper 30s at the coast.

Friday through Saturday: High pressure will prevail across the region through Saturday. The forecast is dry thanks to precipitable water values falling to as low as 0.10" during the period. Temperatures will be below normal, with highs in the low to mid 50s and lows falling into the 20s for much of the area Friday night

Long Term - Saturday Night Through Wednesday
Dry weather and moderating temperatures expected Saturday night through Tuesday as high pressure gradually shifts east. A mostly dry cold front will sweep through Tuesday night, followed by a considerable cool down.

Marine Discussion
Tonight: Hazardous conditions expected as a strong low-level jet moves across the area ahead of a cold front which will be nearing the coast toward daybreak. We think the the best prospects for gale force gusts near 35 knots will be near the warmest waters of the Gulf Stream and thus have Gale Warnings for a portion of the waters with solid Small Craft Advisories elsewhere. However, all waters could see gale force wind gusts, especially associated with strong showers and thunderstorms late tonight. Lastly, there is a small risk of sea fog this evening ahead of the front as low-level moisture increases but before winds increase substantially.

Thursday through Monday: Strong winds and dangerous marine conditions are expected for the first part of Thursday morning as a strong cold front moves through the local waters. Gale Warnings are in effect everywhere other than the nearshore Georgia waters and the Charleston Harbor. Once the front moves through, conditions should quickly improve by late morning such that the warnings will expire and be replaced with Small Craft Advisories. Westerly winds will remain elevated Thursday afternoon and night, and seas will steadily decrease as well. The Small Craft Advisory could linger in the outer Georgia waters into Friday morning, but all others should come to an end Thursday night. Thereafter, high pressure will build in and prevail through the weekend. Winds and seas are expected to remain below critical thresholds through that time

NOAA Charleston SC Office: Watches - Warnings - Advisories
GA...None. SC...Lake Wind Advisory from 4am to 10am EST Thursday for SCZ045.
MARINE...
Gale Warning until 10am EST Thursday for AMZ350-352-374.
Small Craft Advisory until 4pm EST Thursday for AMZ330-354

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