Marine Weather and Tide Forecast for Barnwell, SC

NEAR TERM /THROUGH TONIGHT/
Key Message(s):

- Chance for afternoon and evening showers and thunderstorms

Upper low has moved over Tennessee this afternoon. A weak shortwave moving through South Carolina has sparked a few thunderstorms in the central to northern Midlands into the PeeDee. Expect these storms to move out of the area. Additional isolated showers and thunderstorms are possible later this afternoon into the evening. The severe threat is very low (<5%) for any new development the rest of the day. After sunset, the shower and thunderstorm activity is expected to wane as we lose the daytime heating. The upper low begins to move away from the area overnight, also aiding in the reduction of shower and thunderstorm activity. Temperatures overnight are expected to be on the mild side, mainly in the mid 60s.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
Key Message(s):

- Isolated to scattered showers and thunderstorms Wednesday, especially across the Pee Dee and eastern Midlands.

- Warmer and dry on Thursday.

Wednesday and Wednesday Night: The upper trough to our northwest at the start of the day heads northeast in response to building upper ridging moving in from the west. This timing is faster than in previous model runs. With the best forcing moving away earlier than anticipated, CAMs have decreased coverage across our forecast area. PoPs have been lowered on Wednesday in response to this, with the highest values across the Pee Dee which will be closest to the best upper lift in the afternoon.
Convection is likely to peak in the early afternoon, with rain chances decreasing from southwest to northeast Wednesday evening and into the overnight hours. The SPC has also made changes to their Day 2 SWO, moving the Marginal (1/5) severe risk further northeast but still across the Pee Dee and eastern Midlands.
Daytime temperatures should be similar to today with forecast highs in the upper 70s to lower 80s, falling into the mid-60s at night.

Thursday and Thursday Night: Upper ridging continues its eastward movement on Thursday, while surface high pressure strengthens in the eastern Gulf. The ridging should create enough subsidence to prevent convective development, though with PWATs around 1.5 inches, scattered cumulus will likely develop in the afternoon. Daytime temperatures will be warmer with near to above normal values expected. It will likely be balmy outside during peak heating with forecast dewpoints in the upper 60s and heat index values around 90 degrees.

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

- Hot and humid conditions likely Friday, continuing into the upcoming weekend. Heat index values could approach 100 degrees during peak heating on Friday.

- Diurnally driven shower and thunderstorms chances each day.

Axis of upper ridge will be in our vicinity at the start of the extended, flattening out in response to trough passing along the US-Canadian border through Sunday. This should result in above normal temperatures across our forecast area through the period. Friday currently appears to be the hottest day of the the long term and will combine with high dewpoints to create heat index values around 100 degrees during peak heating. This will be the first period of summer-like conditions in our area this year, therefore caution should be exercised should these conditions manifest and you have outdoor plans Friday afternoon.
A cold front is expected to move into our FA Saturday night, potentially stalling near/over the region. This boundary could serve as a lifting mechanism for daily shower and thunderstorm chances. Uncertainty is higher than usual, therefore PoPs are generally at or below 20 percent through the extended.

AVIATION /18Z TUESDAY THROUGH SUNDAY/
Generally VFR conditions anticipated throughout the TAF period.

A cumulus field is being noted across the area with some scattered showers and storms northeast of the terminals.
Additional isolated activity is anticipated to develop through about 01z, there is uncertainty whether the terminals will be affected. Confidence is "highest" at CAE/CUB, so kept the PROB30 there and dropped it at the other terminals. Latest guidance is indicating some mid to high level cloud cover, which should reduce the chance for stratus and fog. However, if skies do clear, there is a chance for lower cigs or vis. Winds out of the south-southwest this afternoon of 5-10 kts expected, becoming light and variable after 01z. Winds increase out of the southwest once again after about 14z.

EXTENDED AVIATION OUTLOOK...Periods of rain and thunderstorms continue through tomorrow evening as moisture feeds into the region. The threat for restrictions decreases for the end of the week.

HYDROLOGY
Recent heavy rainfall has produced widespread amounts of 3 inches over the past 5 days, with amounts of up to 6-7 inches in some locations. As a result, river flooding along the Congaree River from Columbia to Gadsen is expected. In addition, Lake Greenwood increased their releases, cause the Saluda River at Chappells to go into flooding today as well. River flooding is also possible along the Edisto River at Orangeburg, PeeDee River at Cheraw, and the Wateree River just below the Lake Wateree Dam. Will continue to monitor these locations for the need of additional flood warnings.

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