Public Information Statement
Issued by NWS Charleston, SC

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254 NOUS42 KCHS 010724 PNSCHS GAZ117-119-139-141-SCZ048>052-020730- Public Information Statement National Weather Service Charleston SC 324 AM EDT Thu Aug 1 2019 ...A REVIEW OF THE NATIONAL WEATHER SERVICE COASTAL FLOOD PROGRAM... The National Weather Service in Charleston is responsible for the dissemination of coastal flood watches, warnings and advisories as well as high surf advisories for all of south coastal South Carolina and north coastal Georgia. Forecasters use a variety of data sources to help monitor and forecast tidal levels along the coast. These sources include but are not limited to tide gages operated by NOAA`s National Ocean Service (NOS) at Charleston Harbor SC and Fort Pulaski Georgia. ...COASTAL FLOOD ADVISORY... Unique topography and large tidal ranges make south coastal South Carolina and north coastal Georgia highly susceptible to astronomical high tides associated with the lunar cycle. Forecasters will issue a coastal flood advisory whenever tide levels are expected to meet or exceed established thresholds for shallow coastal flooding. Shallow coastal flooding typically begins along the lower South Carolina coast when water levels reach 7.0 ft mean lower low water (MLLW) in the Charleston Harbor and across north coastal Georgia when levels reach 9.2 ft MLLW at Fort Pulaski. Impacts: only minor impacts can be expected during shallow coastal flooding events. Some minor inconveniences from standing sea water may occur particularly if rain falls during the high tide cycle. This is because storm drains that usually empty into marshes, rivers or harbors may become backed up with sea water. If heavy rains develop during this time, a more substantial flood threat could develop since storm drains will be full. Downtown Charleston is particularly vulnerable to flash flooding when heavy rains occur during an astronomical high tide. ...COASTAL FLOOD WATCH... Forecasters will issue a Coastal Flood Watch when significant damage from moderate to severe coastal flooding is possible within 12 to 36 hours, but the severity and timing of the highest tides are still somewhat uncertain. Significant flooding and damage typically begins across south coastal South Carolina when tide levels reach 8.0 ft MLLW in the Charleston Harbor and 10.0 ft MLLW at Fort Pulaski. These tides typically pose a significant risk to both life and property for those living along beach fronts as well as the adjacent marshes, rivers, sounds and harbors. ...COASTAL FLOOD WARNING... Forecasters will issue a Coastal Flood Warning when there is a high probability that damage from moderate to severe coastal flooding will occur, usually within 12 hours. A risk to both life and property exists. Impacts: Significant impacts can be expected. These include but are not limited to severe beach erosion, strong rip currents and significant ocean overwash which may result in damage to nearby structures and roads. Access roads to the beaches and barrier islands may become cut off for several hours prior to and after high tide. Highway 80 heading to Tybee Island from Savannah is particularly vulnerable to becoming inundated and impassable during coastal flood situations. ...HIGH SURF ADVISORY... A High Surf Advisory is issued by forecasters whenever seas of 8 ft or higher are expected to occur across the coastal waters or if breakers of 5 ft or greater are expected to occur within the surf zone. $$

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