Marine Weather and Tide Forecast for Barnwell, SC

NEAR TERM /UNTIL 7 AM SATURDAY MORNING/
Key Message(s):

- A few showers or thunderstorms are possible towards daybreak across our northern and western counties.

Temperatures have slowly begun to fall as the sun lowers to near the horizon. The fall should accelerate for a couple of hours immediately after sunset with the loss of daytime heating.

We then turn our attention toward the severe convection over the lower Ohio Valley. The thunderstorms should make steady progress toward the southeast late tonight and start to approach the upstate during the early morning hours. However, mid level support for thunderstorms is much lower in our area by sunrise, so expect just remnants to approach the northwestern CWA with possibly a few showers and an isolated thunderstorm by daybreak.



SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/
Key Message(s):

- An approaching cold front could spark a few showers or thunderstorms Saturday morning and again Sunday afternoon.

- Winds may be breezy at times on Saturday, especially over area lakes.

- Continued warm and humid through the weekend.

Guidance continues to show a weak cold front passing through the region on Saturday. Rain chances continue to decrease and will be highest in the morning across our northwestern counties and the CSRA associated with the aforementioned decaying convection. The 12Z HRRR in particular shows a complex of thunderstorms moving into the CSRA from the west so maintained Slight Chance PoPs there while decreasing them below 15 percent elsewhere. SPC maintains a Marginal (1/5) risk for severe weather in their latest Day 2 SWO so will continue to monitor new guidance and update the forecast as needed. However, at the moment any severe threat should be isolated. It will be breezy at times across the forecast area on Saturday, especially on area lakes. Latest guidance shows some lakes, especially Lake Murray, near Lake Wind Advisory criteria. Since its is only marginal at this time, will hold off on issuing a LWA with this forecast package. With more clouds around, temperatures should be slightly cooler than today albeit still above seasonal values.

The front may stall near the region on Sunday keeping clouds in place. In addition, our Georgia counties are in a Marginal (1/5) risk for severe weather in the SPC Day 3 SWO. This is where Slight Chance PoPs are maintained for Sunday afternoon.
Many locations could remain rain free through the weekend but everyone should stay weather aware in case an isolated thunderstorm approaches your area. Temperatures Sunday should be a degree or two lower than on Saturday but once again above average.

LONG TERM /MONDAY THROUGH FRIDAY/
Key Message(s):

- Warm and humid conditions continue, with showers and thunderstorms possible each afternoon through mid-week.

Upper ridge axis will shift across the CWA on Monday. Low pressure in the central Plains and Mississippi Valley will reactivate the stalled front over GA/SC that day; it will advect NE'ward from then through Wednesday. There remains some disagreement among models how quickly this occurs. A gradient of instability from SW to NE across the CWA is likely Monday, but the strength of any cap appears uncertain at this time, and other than the general weak forcing associated with the front, we may be for want of a triggering mechanism. There remains some indication from the global models that a convectively generated shortwave will round the ridge Monday which could promote initiation.
For now a mostly slight-chance to chance PoP appears appropriate. By Tuesday chances shift mainly from Columbia northeast nearer the front, with profiles drying aloft from the southwest making convection less likely. Temperatures will trend warmer over these two days, with much of the area within a couple degrees either side of 90. Enough 0-6km shear will be present those days that if any convection does fire some damaging wind or large hail are not out of the question; confidence remains low partly due to the spread in depicted CAPE.

Pattern change will begin by Wednesday as central CONUS trough pushes into the East. Guidance has come into better agreement in how this pans out, notably the Canadian GDPS/GEPS having trended faster and less supportive of an upper low cutting off. PoPs rise to likely Wed as the shortwave and sfc reflection pass by to our north. Severe threat likely will be greatest that day as cold front moves in and 0-6km shear peaks at 50-60 kt. Temps will fall back into the mid 80s Wed under cloud cover, and then at or below normal Thursday with less humidity.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/
Mainly VFR Conditions Expected through the TAF Period.

Plenty of high level cloudiness will be streaming across the region overnight and through much of the day on Saturday. This should be the primary cloud group for much of the period at all taf locations. Exception may be at ags/dnl sites Saturday morning shortly after sunrise, where a brief ceiling around 5kft may be found as diminishing area of showers moves in from the northwest ahead of an approaching cold front. Most guidance is indicating that showers will be all but gone as these clouds push through the CSRA, and will no longer include any vcsh at those locations due to low confidence. Otherwise, southwesterly winds should be stronger at the TAF sites on Saturday as the front passes through the region, with some wind gusts around 25 knots at all taf locations during the afternoon hours.

EXTENDED AVIATION OUTLOOK... Mainly VFR conditions expected through the period barring low end chances for showers and thunderstorm each afternoon which could cause brief restrictions.

HYDROLOGY
Most rivers are either near crest, or have already crested and are falling. River flooding remains along the the Congaree River, and long both the North and South forks of the Edisto River. River levels will continue to fall through the weekend.

CAE WATCHES/WARNINGS/ADVISORIES
SC...None.
GA...None.