textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Below normal temperatures and gusty winds expected this weekend as a powerful nor'easter develops off the North Carolina Outer Banks and high pressure prevails inland. - 2) High surf and dangerous rip currents possible into early next week.

DISCUSSION

KEY MESSAGE 1: Below normal temperatures and gusty winds expected this weekend as a powerful nor'easter develops off the North Carolina Outer Banks and high pressure prevails inland.

Through Tonight: Currently observing some isolated and weak showers/sprinkles primarily across the SC Lowcountry this afternoon, likely tied to the lift of the approaching upper level trough. As the trough swings through this afternoon, the very light rainfall will end. Otherwise, behind the cold front that passed through earlier this morning, breezy northerly winds will persist throughout the rest of the afternoon hours. Wind gusts of 25-35 mph are expected across majority of the area, highest across the SC Lowcountry. In addition, can't rule out wind gusts approaching 40 mph over elevated bridges and overpasses along the coast, leading to difficult driving conditions for high profile vehicles. Throughout the afternoon hours and evening hours, cold air advection will be increasing as cold air pours in, which will also help to keep breezy conditions going into the overnight hours. Expect crisp overnight lows to dip down into the mid to upper 40s across the area, perhaps lower 50s for those along the immediate coastline. Combined with the breezy winds, wind chills in the upper 30s to lower 40s are possible away from the immediate coast before the sun rises, so be sure dress appropriately if you're heading out early Sunday morning.

Sunday: Behind the exiting trough axis, upper level ridging will lead to a strengthening surface high pressure over the Mid-Atlantic states, with the southern extent making its way into the Southeast. As the aforementioned trough axis moved off into the Atlantic, a strong Nor'easter is expected to develop, resulting in the enhanced surface pressure gradient continuing across the region. Thus, north- northeasterly winds will be gusty in the 20-25 mph range across the region, closer to 30 mph along the coastline. With h925 temperatures peaking in the 8-10 deg C range, temperatures will remain well below normal in the mid to upper 60s across the region. On the plus side, much drier air moves in overhead, so ample sunshine will be present amidst the cooler and gusty conditions.

Next week: The region remains under the influence of the surface high pressure to our north, with the nor'easter slowly moving to the northeast away from the area through mid-week. This will result in warming temperatures through Tuesday, though some weak gusty winds will persist. Afternoon highs on Monday in the mid 60s to lower 70s, warming into the lower to mid 70s on Tuesday and Wednesday. Dry conditions are expected to

Lake Winds: Winds on Lake Moultrie have been sustained 20-25 kt with gusts to 30 kt today, with these hazardous conditions expected to persist into the overnight into Sunday. Waves of 2-3 ft are possible with isolated higher sets possible. Some minor lakeshore erosion and overwash induced by significant wave action could along occur along the south end of the lake, including Pinopolis, Lions Beach and Short Stay. Winds will diminish at for Sunday, but will remain elevated with gusts to 25 kt. A Lake Wind Advisory remains in effect through early Monday morning.

KEY MESSAGE 2: High surf and dangerous rip currents possible into early next week.

High Surf: Prolonged gale force winds with a continuous north- northeast fetch in place will generate large breaking waves along the SC/GA beaches Sunday into Monday. The largest breakers are expected along GA beaches due to a more favorable onshore flow. Although latest guidance has come in slightly weaker in regards to wind speeds, the prolonged/favorable fetch continues to support +5 ft breakers along GA beaches on Sunday. A High Surf Advisory has been issued for this area from midnight tonight through noon Monday as a result. Additionally, minor beach erosion is possible along the coast, perhaps with some local enhancement during high tide cycles Sunday and Monday.

Rip Currents: Strong/gusty winds, building waves, and long period swell associated with a favorable north-northeast fetch along the Southeast Coast will support a Moderate Risk for rip currents along all beaches today, followed by a High Risk for rip currents Sunday. An enhanced period of rip currents is likely to continue through early next week.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Scattered MVFR cigs are observed this afternoon roughly along and east of I-95, with some nuisance sprinkles possible for a few more hours across the South Carolina Lowcountry. Breezy northerly winds will continue throughout the afternoon hours, weakening a little during the late evening and overnight hours. Dry on Sunday, with gusty to breezy northeasterly winds.

Extended Aviation Outlook: After breezy conditions dissipate Sunday into Monday, no high confidence extended aviation concerns..

MARINE

Through Tonight: Dangerous marine conditions will persist across local waters this afternoon and through the night as strong cold air advection occurs with building high pressure in wake of a cold front advancing further offshore. Strong/gusty north-northwest winds will gradually turn north-northeast this afternoon, generally between 25- 30 kt with gusts upwards to 35-40 kt expected across all waters outside the Charleston Harbor. However, a few gusts to gale force are possible across the Charleston Harbor late day/tonight as peak wind gusts for the event arrive when cold air advection is strongest and helps tap into 40-50 kt 1000mb lvl geostrophic winds. Seas will also build throughout the day, increasing to 6-9 ft across nearshore waters and 9-12 ft offshore overnight. Seas could even build up to 2- 4 ft across the Charleston Harbor tonight. Given ongoing conditions and expected trends, Gale Warnings will remain in effect for all nearshore and offshore SC/GA waters through the night while a Small Craft Advisory remains in effect for the Charleston Harbor.

Sunday through Wednesday: Dangerous marine conditions will be ongoing to start off next week with Gale Warnings in effect into Monday for nearshore and offshore SC/GA waters while a Small Craft Advisory remains in the Charleston Harbor. Latest guidance has come in a bit weaker in regards to the strength and duration of gusty north/northeast winds early next week, which could result in a shortening of these hazards early Monday. However, low pressure forming well of the coast of the Outer Banks of NC early week should help maintain a period of Small Craft Advisory level conditions across local waters into Tuesday, while lingering 6-7 ft seas across GA waters could result in longer duration Small Craft Advisories through mid week.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Surf Advisory from midnight tonight to noon EDT Monday for GAZ217-219-239-241. SC...Lake Wind Advisory until 2 AM EDT Monday for SCZ045. MARINE...Small Craft Advisory until 8 AM EDT Monday for AMZ340. Gale Warning until 8 AM EDT Monday for AMZ360-362-364. Gale Warning until 8 PM EDT Monday for AMZ380-382-384.