Marine Weather and Tide Forecast for Bluffton, SC

NEAR TERM /THROUGH TONIGHT/
The upper-level flow across the region will remain fairly zonal through tonight with the area placed between a shortwave ridge passing by to the north and a southern stream system meandering over the Gulf. Surface high pressure to the north will continue to wedge south through tonight inducing a weak coastal trough just offshore. The surface high looks to remain fairly transient given the zonal flow aloft and is forecast to shift offshore of the Virgina Tidewater by daybreak Tuesday. Lows from the 06/13z NBM range from the upper 40s well inland to the lower-mid 60s at the beaches; however, these are likely a tad too high away from the coastal corridor where some boundary layer decoupling and better radiational cooling should occur. Despite this, the official forecast did not deviate from the NBM as national "Break the Glass" criteria is not being met and local adjustments are prohibited in these instances.

Shallow ground fog and stratus will likely develop early Friday morning, similar that was observed this morning. Model 1000 hPa condensation pressure deficits are forecast to remain high, so any fog that forms will likely remain fairly shallow, although possibly locally dense. The risk for dense, shallow ground fog will be highest across interior Southeast Georgia and along the Altamaha River, but widespread, significant impacts are unlikely.

SHORT TERM /FRIDAY THROUGH SUNDAY/
Friday and Saturday: Aloft will feature zonal flow, with a shortwave trough rippling across the Mid-Atlantic states Saturday morning. At the surface high pressure will dominate into the weekend. Apart from a slight chance of rainfall far inland early Saturday morning, the forecast remains dry across the region. Temperatures will be 5 to 7 degrees above normal, with highs reaching into the upper 70s to low 80s across SE GA.
Overnight lows will similarly be above normal, only dropping into the upper 50s to low 60s.

Sunday: The pattern begins to shift on Sunday as an anomalously deep upper level trough digs across the CONUS. At the surface a strong cold front will approach the region. Warm air advection ahead of the approaching cold front will allow temperatures to reach into the upper 70s to low 80s once again. A line of showers and maybe some thunderstorms is forecast to push through the region ahead of the cold front. Forecast soundings show PWATs around 1.1-1.3" and CAPE values 500-800 J/kg, however forecast soundings remain very dry. Therefore, PoPs remain quite meager with this front with only isolated to maybe scattered showers and thunderstorms forecast and meaningful rainfall hard to come by.

LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
The aforementioned strong cold front will push through the region Sunday night. Any lingering showers will push offshore quickly, with a dry forecast beginning just after midnight. The big highlight of this front will be the cold temperatures.
Overnight lows on Sunday night will dip into the low 40s inland and around 50 along the coastline. Heading into Monday these temperatures will warm very little, with Monday highs only forecast to reach into the low to mid 50s. Gusty NW winds are also expected Monday, with gusts approaching 25 knots on Lake Moultrie. A Lake Wind Advisory may be required.

Low temperatures on Monday night heading into Tuesday morning will be the coldest of the season, and likely the first widespread freeze across the region. Temperatures are forecast to reach the mid to upper 20s inland, with freezing temperatures extending into the coastal counties (away from the immediate beaches). A Freeze Watch/Warning will likely be required for most, if not all, counties. These low temperatures could approach the record at all three climate sites in the area.

Tuesday's high temperatures will be a few degrees warmer than Monday, however still significantly below normal, only reaching into the 50s once again. Tuesday night features temperatures around freezing far inland, with upper 30s to low 40s along the coast. Frost/Freeze could be required, unless Monday night's widespread freeze ends the growing season across the region.

Zonal flow develops aloft mid-week with high pressure dominating at the surface, allowing temperatures to moderate closer to November normals by the end of the period.

AVIATION /15Z THURSDAY THROUGH MONDAY/
06/18z TAF Discussion: KCHS/KJZI/KSAV: VFR will prevail for much of the 18z TAF period.
Shallow ground fog development is possible at mainly KJZI and KSAV prior to daybreak Friday. There may be a brief period of MVFR vsbys if the shallow fog layers can become deep enough, but confidence on this is only medium at best. TEMPO groups for 4SM MIFG were highlighted 10-13z for now to account for this possibility. Adjustments may be needed for later TAF cycles.

Extended Aviation Outlook: VFR conditions expected to prevail.

MARINE
Through Tonight: Northeast winds will generally prevail through tonight as a wedge of high pressure lingers inland and a coastal trough develops just offshore. Although a brief surge as high as 15-20 kt could occur for a few hours this afternoon along parts of the South Carolina nearshore waters, winds should generally average 10-15 kt with seas 3 ft or less.

Friday through Monday: Generally quiet marine conditions are forecast Friday and Saturday as high pressure dominates, with winds generally less than 10 knots and seas averaging 2 to 3 ft.
A strong cold front will push through the region Sunday night into Monday, with a surge in NW winds and building seas forecast. Winds Monday into Tuesday are forecast to reach 25 to 30 knots across all waters, outside of the Charleston Harbor where gusts could approach 25 knots. Additionally, there is the potential for the Charleston County nearshore waters and the 20 to 60 nm offshore GA waters to see gale force gusts. Small Craft Advisories are likely for all waters, with a Gale Watch/Warning not out of the question for a portion of the waters. Seas are forecast to peak Monday night into Tuesday with 4 to 6 ft across the nearshore waters and 7 to 8 ft in the 20 to 60 nm offshore GA waters.

TIDES/COASTAL FLOODING
Charleston and Coastal Colleton (Charleston Harbor Tide Gage): The next chance for coastal flooding will be with the Friday morning high tide around 9 am. Anomalies were running negative earlier today due to offshore winds, but the brief switch to northeast winds should cause tide levels to rise back above astronomical values later today. Given that the forecast astronomical tide for Friday morning is 7.1 ft MLLW, even a zero anomaly would produce minor coastal flooding.

Beyond Friday we don't expect any further flooding issues as the astronomical values drop off about 0.2 ft each day and wind directions will become offshore.

CHS WATCHES/WARNINGS/ADVISORIES
GA...None.
SC...None.
MARINE...None.