Marine Weather and Tide Forecast for North Charleston, SC

KEY MESSAGES
- 1) Above normal temperatures and dry conditions are expected through this evening.

- 2) Below normal temperatures and gusty winds expected this weekend in the wake of a strong cold front.

DISCUSSION
KEY MESSAGE 1: Above normal temperatures and dry conditions are expected through this evening.

Today and Tonight: Aloft, the pattern will feature a broad high centered across the western Atlantic and a sharp/digging trough extending across the Great Lakes into the Central Plains. The trough will advance across the East CONUS during the day, helping force a strong cold front east-southeast toward the Southeast United States throughout the day and evening, before entering the local area during early morning hours Saturday. Ahead of the front, a somewhat breezy south-southwest sfc wind (gusts to 15-20 mph) will help support temperatures well above normal within the warm-sector, with afternoon highs generally in the mid-upper 80s locally. Daily record highs are at or above 90 at both CHS and SAV (see Climate section), so it remains unlikely that records will be tied or broken.

Mild temps (low-mid 70s) will persist ahead of the front this evening, but will quickly cool once fropa occurs late night, generally into the upper 50s inland to low-mid 60s near the coast before sunrise. Latest guidance continues to indicate a limited moisture supply near and shortly post fropa, supporting a few showers with light precip accumulation across northern areas after daybreak Saturday.

KEY MESSAGE 2: Below normal temperatures and gusty winds expected this weekend in the wake of a strong cold front.

A potent upper-level trough will drive a strong cold front off the coast early Saturday morning. In its wake, strong high pressure centered over the Central Plains will build eastward toward the Ohio Valley, tightening the pressure gradient. Strong cold air advection will begin to take hold Saturday afternoon, dropping temperatures below early-autumn normals. Daytime highs on Saturday will top out in the mid to upper 60s across most inland areas, with lower 70s confined to the far southern Georgia coast. Lows Saturday and Sunday nights will plummet into the 40s inland, with low to mid 50s along the immediate coastline. Sunday will be the coolest day of the stretch despite abundant sunshine, with highs struggling to reach the low to mid 60s. Temperatures will slowly rebound early to mid next week.

In addition to the cooler temperatures, breezy conditions will quickly develop behind the front. Winds will increase noticeably across the area Saturday morning as strong surface high pressure builds in from the west. Expect sustained winds of 15 to 20 mph with frequent gusts of 30 mph across the area Saturday into Sunday.
Slightly higher gusts are possible along the immediate coast and over elevated bridges and overpasses. While winds remains just shy of Wind Advisory criteria, conditions will remain quite gusty.
Across Lake Moultrie, cold air moving over the relatively warm lake waters will produce gusts of 25-30 kt and rough chop. A Lake Wind Advisory has been issued starting Saturday morning through Sunday evening.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
VFR conditions are expected at CHS/JZI through at least 10Z Saturday and likely prevail at SAV through 18Z Saturday. However, a cold front will shift across all terminals prior to/near daybreak Saturday, resulting in a sharp wind shift (south-southwest to northwest, then north) and increasingly breezy conditions (gusts 15- 25 kt) mid morning Saturday into early afternoon.

A few showers could accompany the front, impacting the CHS/JZI terminals between 10-16Z Saturday. MVFR cigs are expected to arrive behind the front at CHS/JZI, starting around 13Z Saturday and persisting through 18Z. VCSH has been added to CHS/JZI between 10- 13Z, followed by PROB30 groups with showers and low-end MVFR conditions between 13-16Z Saturday. Shower and flight restriction activity is not anticipated at SAV at this time.

Extended Aviation Outlook: Frequent gusts around 25 kt will occur at the terminals Saturday morning into Monday.

MARINE
Today through Tonight: A strong cold front will approach the Southeast United States today, before reaching the coast late tonight/near sunrise Saturday. Ahead of the front, southwest flow will increase to 10-15 kt through the afternoon with a few gusts around 20 kt possible, primarily across SC waters. Overnight, winds will continue to increase as the pressure gradient tightens near/along the approaching cold front, then sharply change direction to northwest/north by around sunrise. Strong cold air advection near and post fropa will set the stage for sustained 15-20 kt winds with gusts to around 25 kt. Seas will also build during the night, generally to 2-4 ft through sunrise.

Extended Marine: A strong cold front will push offshore early Saturday morning as high pressure builds eastward from the Central U.S. Marine conditions will deteriorate rapidly through Saturday as intense cold air advection streams over warm sea surface temperatures. A brief period of Small Craft Advisories Saturday morning will quickly escalate to widespread Gale Warnings for all our marine zones out to 60 nm by the afternoon. Strong north- northeast gales are anticipated Saturday night through Monday morning, featuring sustained winds of 25-35 kt with frequent gusts of 35-45 kt. Hazardous seas will build rapidly, peaking at 7 to 11 feet in the nearshore waters and 11 to 15 feet across the outer Georgia waters. Winds will begin to ease late Monday night, but elevated seas will necessitate extended Small Craft Advisories through at least mid-week.

High Surf: Prolonged gales and a continuous north-northeast fetch will generate large breaking waves of 5+ feet along area beaches Sunday into Monday, with the highest breakers along the southeast Georgia beaches. High Surf Advisories remain likely for the entire coast. Additionally, prolonged wave action could result in minor to moderate beach erosion.

Rip Currents: The combination of strong/persistent gales, elevated seas, and building long-period swell will support a Moderate Risk of rip currents at all area beaches Saturday. A High Risk is expected for all beaches on Sunday, with an elevated risk persisting well into next week as hazardous marine conditions continue.

CLIMATE
Record High Temperatures:

October 16: KCHS: 90/2018 KCXM: 88/2018 KSAV: 91/2018

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...Lake Wind Advisory from 6 AM Saturday to 2 AM EDT Monday for SCZ045.
MARINE...Small Craft Advisory from 6 AM Saturday to 2 PM EDT Monday for AMZ340.
Small Craft Advisory from 6 AM to noon EDT Saturday for AMZ360- 362-364-384.
Gale Warning from noon Saturday to 2 AM EDT Tuesday for AMZ360- 362-364-380-382-384.