textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) A cold front will push across southeast Georgia and southeast South Carolina today, bringing a line of showers across the region as well as gusty winds.

- 2) Minor coastal flooding is expected this morning across coastal portions of Charleston and Colleton counties.

- 3) There is a High Risk for rip currents along the Charleston County beaches today.

DISCUSSION

KEY MESSAGE 1: A cold front will push across southeast Georgia and southeast South Carolina today, bringing a line of showers across the region as well as gusty winds.

Early this morning, surface analysis shows the main front sits just to our west and runs north/south across central GA. There is good model agreement that the front will steadily push eastward this morning, entering our interior GA counties around 4 am then exiting east of Charleston by around 12-1 pm. In the pre-frontal environment, precipitable water values are quite high and will continue to run in excess of 2.25 inches. Forcing along the front and in the low-level jetting ahead of it will be sufficient to drive a band of passing showers with the front. In the pre-dawn hours, there will be some embedded elements of moderate to even heavy rainfall but shower motion should be fast enough to keep the flooding threat quite low. Also, there shouldn't be sufficient instability for anything other than showers.

At sunrise, the front and associated band of showers is progged to be near the Savannah area and the along the Savannah River. This would put the band of showers into the Charleston area around 10-11 am and exiting east after noon. Based on this timing, there likely won't be enough time to allow instability to get too high, but there could still be 500-1,000 J/kg. So, there could be a few rumbles of thunder. Model soundings also show a decent uni-directional wind field, with 30-40 knots centered around 850-900 mb. Therefore, these showers and embedded thunderstorms could be capable of producing some gusty winds but will likely remain sub-severe. Behind the front, winds will turn west-southwest and could produce some gusts into the 25-30 mph range through the afternoon.

KEY MESSAGE 2: Minor coastal flooding is expected this morning across coastal portions of Charleston and Colleton counties.

Minor coastal flooding is expected to occur with the upcoming high tide (~9:15 am) across coastal Colleton and Charleston counties. The astronomical high tide is 6.56 ft MLLW and as we approach low tide (~3 am) the tidal departure is running over 1 ft. Winds will become less supportive of large tidal departures as they turn more southerly and eventually southwesterly over the next few hours. But, we should still see enough departure to produce minor coastal flooding and a Coastal Flood Advisory is in effect.

KEY MESSAGE 3: There is a High Risk for rip currents along the Charleston County beaches today.

The combination of lingering elevated swell combined with breezy southwesterly flow will support a High Risk for rip currents through the evening along the Charleston County beaches. Otherwise, there is a Moderate Risk of rip currents for all other beaches.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

The 12z TAF period begins with MVFR ceilings either impacting or nearby KCHS, KJZI, and KSAV. The main forecast challenge will be timing in the passage of a front and associated showers from the west. This feature has already pushed through KSAV. Current timing would suggest the line will reach KCHS and KJZI around 13z and will exit to the east by around 15z. Most of this activity is just showers, though there have been a few lightning strikes noted, so we might have to amend to add in thunder. Southwest winds will strengthen and become breezy ahead of the front, then turn more west-southwesterly behind the front with gusts up to around 25 knots possible. Gusts will end around sunset and VFR conditions will prevail behind the front through the end of the TAF period.

Extended Aviation Outlook: VFR.

MARINE

Today: Breezy west-southwesterly flow at 15 to 20 kts with gusts up to 25 to 30 kts will continue throughout the day as the remnants of Post-Tropical Cyclone Isaias pass well to the west of the region. Therefore, Small Craft Advisories remain in effect from the for the nearshore waters and outer Georgia waters for the majority of the day. In addition, a cold front is forecast to sweep across the local waters this afternoon/evening leading to a more westerly flow for the remainder of the day. There is a chance of showers and thunderstorms ahead of this aforementioned front in the early to mid- morning hours. Also, west-southwesterly swell will briefly surge into the local waters in the early morning and seas will range from 4 to 7 ft across the South Carolina waters and 4 to 6 ft in the Georgia waters. Thereafter, the swell will slowly taper back and seas will decrease to 3 to 5 ft overnight.

Monday into Thursday: High pressure will build in from behind the passage of the cold front and will be the dominant forecast feature over the next several days. Expect wind speeds to remain relatively breezy on Monday morning, before tapering off through the afternoon and remaining around 5 to 10 kts for the rest of the forecast period. Seas will range from 2 to 3 ft.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Coastal Flood Advisory until 11 AM EDT this morning for SCZ149- 150. High Risk for Rip Currents through this evening for SCZ150. MARINE...Small Craft Advisory until 11 PM EDT this evening for AMZ360- 362. Small Craft Advisory until 2 PM EDT this afternoon for AMZ364. Small Craft Advisory until 8 PM EDT this evening for AMZ384.