Marine Weather and Tide Forecast for Henderson, GA

KEY MESSAGES
- 1) A cold front will pass through southeast South Carolina and southeast Georgia from the north late afternoon into the evening bringing showers and breezy conditions to the area.

- 2) A more impactful system arrives late this weekend, resulting in additional chances for precipitation and perhaps a few thunderstorms.

DISCUSSION
KEY MESSAGE 1: A cold front will pass through southeast South Carolina and southeast Georgia from the north late afternoon into the evening bringing showers and breezy conditions to the area.

Aloft, h5 shortwave energy associated with a broad mid-lvl trough will ripple across the Southeast United States this afternoon, helping produce light rain/showers locally ahead of a cold front arriving from the north late day into early evening hours. Latest radar trends continue to indicate light returns with precip likely struggling to reach the sfc due to substantially air depicted in model soundings from the sfc to 700mb level. However, west-southwest flow ahead of the arriving front should eventually moisten the atmospheric column, supporting measurable rainfall in the form of light to moderate showers across the Tri-County Area and far inland areas of Southeast South Carolina and inland Southeast Georgia early- mid afternoon, followed by activity becoming more focused across coastal areas and Southeast Georgia late day into evening hours as the cold front progresses south with time. Although persistent cloud cover and light rain/showers are expected at times today, warm air advection into the region will still support afternoon highs in the low-mid 70s during peak diurnal heating (warmest across Southeast Georgia into southern Southeast South Carolina). Warming could lead to marginal levels of instability (250-500 J/kg SBCAPE), and when combined with forcing/increasing moisture could even produce a few rumbles of thunder across Southeast Georgia and perhaps as far north into southern Southeast South Carolina late afternoon into early evening. Convection along the front will have the potential for short-lived periods of higher rainfall rates prior to activity shifting offshore and/or south of the Altamaha River by around midnight tonight. Total rainfall amounts should mostly be in the 0.10-0.20" range, but locations that experience a thunderstorm could see amounts in the 0.25-0.50" range.

Ahead of the approaching front, a tightening pressure gradient will yield elevated west-southwest flow across the region, which sets the stage for breezy conditions to continue through afternoon hours while warmer temps promote low-lvl mixing.
Frequent gusts in the 20- 25 mph range can be expected for most areas, with stronger gusts possible during showers and/or an isolated thunderstorm late afternoon into early evening hours.

KEY MESSAGE 2: A more impactful system arrives late this weekend, resulting in additional chances for precipitation and perhaps a few thunderstorms.

Turning the attention towards this weekend, a substantial southern stream shortwave will track into the southeast as a surface low tries to develop off the Mid-Atlantic coastline.
Quite a bit uncertainty remains with this system as it depends on how quickly phasing occurs with this shortwave and the northern stream energy. This significant uncertainty is reflected in the 00Z.LREF cluster analysis where Cluster 1 contains roughly 50% of the ENS members and about 10% of the GEFS members, emphasizing the diversity of ensemble solutions and the lack of a dominant scenario. While, Cluster 2 contains almost the complete opposite scenario with roughly 50% GEFS members and about 10% of the ENS members. Cluster 2 analysis would be supportive with the 06Z.GFS as it displaces the southern stream shortwave farther south and exhibits less phasing relative to the ensemble guidance. This solution would yield a much drier system for the weekend, however as this is just one solution, not much weight has been placed on this scenario quite yet.

Not surprisingly, the 13Z.NBM leans more towards the Cluster 1 analysis and the forecast has been maintained to reflect this.
As the region becomes warm-sectored ahead of an advancing cold front on Sunday, expect precipitation to begin early Sunday and persist into Monday. Regarding rainfall amounts, there continues to be a 80-90% chance of rainfall > 0.5" and a 60-70% chance of rainfall > 1" within a 24-hr period. There is even a possibility of a few weak thunderstorms developing on Sunday afternoon/evening as a little bit of instability appears to be present. These thunderstorms could produce localized pockets of higher accumulations in some areas. As stated before, a lot of uncertainty remains with this system and trends will continue to monitored over the next couple days.

AVIATION /00Z THURSDAY THROUGH MONDAY/
12/00z TAF Discussion: KCHS/KJZI/KSAV: A risk for a brief showers will linger until about 04z at KCHS and KJZI and 06z at KSAV as a cold front drops south through the area. Impacts, if any, will be brief.
Otherwise, VFR will prevail through 13/00z.

Extended Aviation Outlook: VFR prevails through the end of the work week, however flight restrictions are possible this weekend as a system tracks across the region.

MARINE
Tonight: A cold front will push across local waters from north to south this evening. Ahead of this feature, the pressure gradient remains enhanced with low-lvl wind fields and modest mixing supportive of 15-20 kt winds from the southwest this afternoon. Seas range between 2-5 ft, largest across outer Georgia waters.

Guidance continues to support winds veering to the west and weakening into early evening while seas subside and remain below Small Craft Advisory levels through the night. However, northerly winds should eventually surge with cold air advection post FROPA late night, and could briefly result in gusts near 25 kt across outer Georgia waters for a few hours around daybreak Thursday morning. Given the short duration and marginal complexity of the event Thursday morning, have opted to hold off on a Small Craft Advisory across outer Georgia waters with the latest forecast package.

Thursday through Sunday: Breezy northeasterly winds will dial back on Thursday afternoon and tranquil marine conditions should persist through Saturday. Some east-northeastlery swell will linger in the local waters through Saturday as well with seas ranging from 2 to 3 ft. Attention will switch towards a pronounced system heading towards the region late this weekend and south-southeasterly winds will become quite blustery on Sunday. Along with these winds, a good amount of south- southeasterly swell energy should also build into the local waters on Sunday with seas 4 to 7 ft in the nearshore waters and 6 to 8 ft in the outer Georgia waters by Sunday evening.
Therefore, Small Craft Advisories look very likely for late this weekend.

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