Significant coastal flooding is likely early Saturday from a potent northeaster that is expected to develop and move northward, bringing blizzard conditions to parts of North Jersey and New England.

South Jersey may also see a period of potentially heavy snow starting late tonight.

The National Weather Service has issued a coastal flood watch for the entire New Jersey coast for late tonight and into Saturday. Minor flooding is expected this afternoon, but high tide Saturday morning could reach 7.8 feet in Atlantic City, or two-tenths of a foot shy of the major flooding threshold, according to forecasts.

That will translate to moderate to potentially major flooding, especially along the back bay areas, said Gary Szatkowski, meteorologist in charge at the National Weather Service’s Mount Holly office. High tide Saturday morning in Atlantic City comes in at 6:20 a.m., occurring up to two hours later in back bays.

A winter weather advisory also is in effect as of 5 p.m. today until 6 a.m. Saturday for all of South Jersey. Snow totals could be between 1 and 2 inches across much of the region, with a few pockets in western Atlantic County potentially getting four inches, according to weather service forecast maps.

Heavy rain and high winds are expected to affect the region for much of today, with the worst of the winds expected closest to the coast. The rain is likely to change over quickly to snow sometime after 9 p.m., Szatkowski said.

Some area municipalities are already preparing for the potential flooding. Atlantic City is warning residents who live in low-lying sections to move their cars ahead of Saturday morning’s high tide, said emergency management director Tom Foley.

Brigantine Mayor Phil Guenther said public works crews are working to test flood pumps and flood gates. “We’re in the process of filling in along the dune line where our beaches are the narrowest to reinforce the dunes and to close off the street ends that might be open,” he said.

Blizzard warnings are in effect for the New York metro area, including Bergen and Hudson counties in New Jersey, and much of New England. The weather service also has issued “hurricane force wind warnings” just offshore of Long Island and New England.

The storm that will form off the coast is caused by two major systems merging together and then rapidly intensifying, said David Robinson, state climatologist and Rutgers University professor. The storm is forming further to the south than forecasters expected earlier in the week, which will cause higher winds and tides and bring more cold air into the system and to South Jersey, he said.

Szatkowski warned that two impacts from the storm may be worse due to existing damage from Hurricane Sandy — moderate to major beach erosion along the entire oceanfront and back bay flooding in places that are more prone to it following Sandy. Waves during the day today are expected to be between 5 feet and 7 feet in the surf zone, but by Saturday morning’s high tide at about 6 a.m., those waves will be between 6 feet and 8 feet.

“As we know, Sandy rearranged a lot of stuff in the back bay areas,” Szatkowski said of the potential that flooding could occur in places it didn’t prior to Sandy.

As for the beaches, he said, “there’s less of it to be eroded in many cases and it could result in some major impacts because there’s just not as much (sand) there to block the heavy wave action.”

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