NWS: Periods of Heavy Rain Continues Overnight With Ongoing Flash Flood Threat.

The flood threat will continue through the overnight hours across the eastern slopes of the southern Appalachians, including the South Carolina Upstate, western North Carolina, and southwest Virginia. Several areas have already received between 5 and 7 inches of rain, while many others have picked up 3 inches or more in just a few hours. Additional heavy rainfall is expected before daybreak.

The reason this setup has become so concerning is that storms continue to redevelop along the eastern side of the Blue Ridge. Moist air flowing into the mountains is being forced upward, producing repeated rounds of heavy rain over many of the same locations. Instead of quickly moving through, some of these storms have lingered long enough to produce significant rainfall totals.

Earlier forecast guidance suggested the storms might gradually weaken overnight, but that simply hasn’t happened. We continue to see plenty of moisture feeding into the region, and there is still enough energy in the atmosphere to keep showers and thunderstorms producing very heavy rainfall. In fact, satellite and radar trends suggest storm coverage has actually expanded in parts of western North Carolina during the past few hours.

The atmosphere remains extremely efficient at producing heavy rain. With abundant moisture in place and a steady upslope wind, rainfall rates of 2 to 3 inches per hour remain possible in the heaviest storms. It won’t take long for additional flooding to develop where those rates occur.

The most significant flooding so far has been reported near the Mount Airy and Pilot Mountain areas, but heavy rain has become increasingly widespread along the Blue Ridge. Some locations across western North Carolina have already picked up 2 to 3 inches, and additional rainfall of 2 to 4 inches remains possible through early morning. Any community that sees storms repeatedly move over the same area could receive even higher totals.

If you live in a flood-prone area, remain weather aware overnight. Creeks and streams can rise quickly, especially in the mountains where water runs off steep terrain much faster than in flatter areas. Conditions can change rapidly while most people are asleep, so make sure you have a way to receive Flash Flood Warnings overnight.

While not everyone will experience flooding, the areas that do could see water rise very quickly. Never drive through a flooded roadway, especially after dark when it’s difficult to judge how deep the water really is. Overnight flooding can be especially dangerous because it’s often harder to recognize the threat until it’s too late.