Key Points:
- Helene is now a Category 2 hurricane over the Gulf of Mexico. The National Hurricane Center expects it to become a Category 3 storm before landfall in Florida. The forecast track has shifted back to the east overnight, and a further eastward shift is possible.
- A Tropical Storm Warning remains in effect for all of South Carolina. Parts of the state are under Flood Watches and Warnings, and a Tornado Watch is in effect for most of the state until 9 p.m.
- The more eastward track increases the risk for damaging winds to affect more of South Carolina, with peak gusts over 70 mph possible in the Upstate, Central Savannah River Area, and western Midlands.
- Flooding rainfall remains a high threat to the Upstate and vicinity, as heavy rainfall has already occurred in this area, and several inches of additional rain will fall. Isolated to scattered instances of flash flooding will affect the rest of the state.
- The potential exists for several tornadoes to occur in South Carolina through tonight as Helene moves through the region. The greatest risk is in the Lowcountry and vicinity, but most of the state is subject to seeing isolated tornadoes.
- A storm surge of 1-3 feet is likely along our coast, highest along the Lowcountry coast. The timing of the worst surge relative to high tide will be the key to the coastal flooding impacts.
Flooding rain and tornado risks are already present in South Carolina well ahead of Helene's arrival tonight. A flood watch is in effect for the Upstate and Central Savannah River Area (CSRA). Here's the current tornado watch outline, in effect until 9 p.m. It will not be our last tornado watch.
Powerful and super-sized Helene will make landfall in Florida this evening and impact the Palmetto State through Friday morning. The storm will weaken slowly as it pushes north across Florida, Georgia, and the Carolinas, so impacts will be widespread across our region.
Extreme rainfall and flooding remain a big concern, particularly across the Upstate and vicinity. There is little change with respect to expected rain and flooding impacts from Wednesday.
'High Risk' areas on the Weather Prediction Center's outlook products are a big deal; about 80% of flood-related property damage and about 40% of flash flooding fatalities occur in areas where they have this outlined. Flooding is and will remain life-threatening in this area. The 'Moderate Risk' areas see a significant amount of damage and deaths as well. So, if you're in these areas, be prepared for flooding, and expect it if you're in a prone area. Remember to never drive through flooded areas. Don't be featured on the local TV news this evening; turn around, don't drown. The heavy rainfall may lead to landslides in the higher ground northwest of I-85.
A change since Wednesday is that the threat of wind damage tonight into early Friday has increased. High winds with peak gusts over 70 mph are possible for the Upstate, CSRA, and western Midlands. If you're trying to read between the lines, I'll be more explicit: the hurricane force range starts at 74 mph, and wind gusts this strong may occur in a few spots. 60 mph gusts may occur along the I-77 Corridor, the rest of the Midlands and Lowcountry; the southern coastal Lowcountry has a chance for gusts over 70 mph. That increases the threat of wind damage; tree and power line damage has the potential to be more widespread for western parts of the state. The concern for wind is less farther east into the Pee Dee region, but that area may still see isolated tree and power line damage from gusts over 40 mph. Be ready for power outages, and there is a chance we see some prolonged outages where these higher winds will strike tonight if restoration crews become overwhelmed.
The tornado risk has also been upped a bit. I showed you the current tornado watch above, below is the Storm Prediction Center's outlook through tonight.
The more serious 'enhanced risk' area, level 3 of 5, has been expanded to cover the entire Lowcountry and some surrounding areas. Please be on your toes and alert for tornado warnings in this area through tonight. Have a plan to move to your best shelter in your home or workplace; you might not have time to think about what to do when a warning comes out. Have multiple ways to receive warnings tonight; have your phone or a weather radio (why not both?) set to alert you if a tornado warning comes out for your area when you're trying to sleep (you might not get much sleep tonight). Remember to go to shelter instead of looking for a tornado when you get a warning; any tornadoes we have through tonight will likely be heavily obscured by rain, anyway.
The storm surge forecast hasn't changed. Water levels will remain elevated with onshore winds through Friday morning along our coast. If the worst of the surge lines up with a high tide, then there could be minor to moderate coastal flooding; should heavy rainfall occur at the same time as well, that would make the flooding even worse.
That about covers it. There are other goings-on in the tropics; there is newly-formed Isaac northeast of Bermuda, and we're about to have a Joyce over the tropical Atlantic, but I think that neither will directly affect us, though we might have beach and boating concerns. We'll worry more about the long-range when we don't have a much bigger largemouth bass filet to bread and fry.