Update: Flood impacts from Hurricane Matthew elevated to ‘extreme’

In the latest forecast, Hurricane Matthew still remains on track to ride up the South Carolina coast then make a dramatic curve out to sea, but weather authorities ramped up flood impacts to “extreme” Thursday afternoon.

More rainfall than previously expected Wednesday is now expected to hammer Grand Strand coastal regions and trees could easily topple from wind gusts.

Increased storm rainfall total amounts with a potential for more than 10 inches along coastal areas was announced as a possibility early Thursday morning, which could lead to road washouts and sinkholes, along with flooding at vulnerable structures in low-lying areas. That statement was echoed in an afternoon update as forecasters stressed extreme flooding was possible.

“Heavy rainfall and flooding is likely, especially during Saturday with rainfall exceeding 10 inches at the coast,” said Steve Pfaff, meteorologist with the National Weather Service in Wilmington, N.C. in a 2 p.m. threat assessment.

A morning update Thursday mostly mirrored previous updates from Wednesday evening with "no significant changes" made to the latest forecast storm track, but showed more rainfall could pound the coastline, Pfaff said.

“A Flash Flood Watch is now in effect for a portion of northeast SC and southeast NC. A Tropical Storm Watch is in effect for the coastal waters from Surf City to the South Santee River out to 20 nm,” said Pfaff Thursday afternoon.

Tropical storm watches may also be needed for land areas and upcoming advisories could be issued.

The update also stated 10 to 14 inches of rain was expected for Horry and Georgetown County coastlines, with 8 to 10 inches likely farther inland in the counties.

"Rainfall will begin during Friday, while direct rainfall associated with Matthew would occur Friday night through Saturday night. Rain may be heavy at times with the risk for flash flooding increasing," said Pfaff, who said the greatest risk of flash flooding would be Saturday night.

A large swath of tropical moisture not associated with Matthew is moving into the area, creating rainy conditions, then influence from Matthew is expected to fuel rainfall.

Tropical storm force winds are also more likely, Pfaff said in the Thursday afternoon assessment.

Moderate storm surge impacts could also occur with 2 to 4 feet inundation north of Cape Fear, N.C. to 4 to 6 feet south of Cape Fear, N.C. with the highest values from Myrtle Beach southward, with the surge’s brunt crashing in Saturday, Pfaff said.

Gusty winds near 60 mph could blow along the coasts with gusts in the 40-50 mph range felt farther inland. Pfaff warned some trees embedded in already saturated soil could easily topple. Downed trees and wind could create power outages and structural damage.

“Large waves for days on end” could result at area beaches as dangerous maritime conditions are likely to last into next week as the storm meanders off the coast, Pfaff said on an 8:30 a.m. conference call Thursday.

As far as Matthew’s path, the storm is still expected to ride along the S.C. coast then make a dramatic curve out to sea with impacts from the hurricane being felt along the Grand Strand late Friday into Saturday night, as the storm likely morphs into a Category 2 storm when it nears Grand Strand-area waters, forecasters said.

Pfaff said huge question marks exists for the storm’s path after it makes its dramatic loop south from the South Carolina coast.

The storm still churns within the cone of uncertainty for South Carolina.

"Do not let your guard down as any adjustment to the west would support greater impacts," said Pfaff in the threat assessment.

The powerful storm weakened some as it interacted with the Bahamas Wednesday, but began regaining some strength as it headed toward Florida Thursday afternoon at about 14 mph as a Category 4 storm with 140 mph, weather authorities said.

No hurricane watches or warnings have been issued yet for Horry or Georgetown counties, but a hurricane watch reached into South Carolina for the South Santee River area early Thursday morning.

Gov. Nikki Haley ordered evacuations for Zone A for Horry and Georgetown counties at noon Thursday. Zone A is the area east of Kings Highway and closest to the coast. An estimated 200,000 could be leaving the coast line Thursday, and officials said they were prepared to enact lane reversals on U.S. 501, but none had been ordered Thursday morning.

Elizabeth Townsend: 843-626-0217, @TSN_etownsend

This story was originally published October 6, 2016 at 6:16 AM with the headline "Update: Flood impacts from Hurricane Matthew elevated to ‘extreme’."