‘Major flooding’ and high winds are possible this weekend in the Philly region

A “hybrid” coastal storm is all but certain to have significant impacts during the weekend throughout the Phillly region, with “major flooding” possible at the Shore along with wind gusts to 60 mph, forecasters are warning.

Areas along the I-95 corridor could experience heavy rains with gusts to 50 mph as the storm tracks ponderously along the Mid-Atlantic coast Sunday into Monday.

Jersey Shore towns already are getting a not-so-dry run this week of what’s expected this weekend. The National Weather Service in Mount Holly has issued coastal flood advisories in effect until 4 p.m. Saturday.

But that flooding would be the result of steady onshore winds and the tug of the waning “supermoon,” not the incipient coastal low, expected to have its biggest impacts Sunday into Monday.

Formerly disputatious computer models have come “into better agreement” on the future of what could be one of the more significant storms to affect the region in recent years, said Sarah Johnson, warning coordination meteorologist in the Mount Holly office.

Said Bob Larson, senior meteorologist with AccuWeather Inc., “This is the real deal.”

Winds and waves are going to rip sand off beaches, as flooding occurs during multiple high tide cycles, Larson said.

While flooding is likeliest in the beach towns and their back bays, which in August sloshed over from the waves generated by Hurricane Erin, NOAA’s Weather Prediction Center warned that inland flooding also was possible.

The storm, which was due to form off the coast of North Carolina, was forecast to intensify over the very warm waters of the Gulf Stream and move up the East Coast.

It will be a “hybrid” cyclone infused with tropical moisture — not a classic cool-season nor’easter, said Larson. AccuWeather is calling it a “tropical rainstorm.”

Larson expressed some surprise that the National Hurricane Center hasn’t considered making it a named storm.

Winds are due to pick up Saturday afternoon, with the strongest gusts from Sunday afternoon into early Monday. Rain is likely to begin late Saturday night or early Sunday and continue into Monday.

At the Shore, where the rains and winds likely will be more robust than on the mainland, a coastal flood watch is in effect from 10 a.m. Sunday through 8 p.m. Monday with “major” flooding forecast for high tide at 1 p.m. Sunday for the oceanfront and back bays.

The moon, which is making one of its closer approaches of the year, is waning, but it is still exerting its influence, Larson said. Plus, “this is going to be a slow-moving system that means we’re going to have several high tides affected.”

Larson said Thursday that the computer model solutions were becoming closer to each to other. The European forecast model had the center approaching Cape May.

Larson said he expected a general 2 to 4 inches of rain at the Shore, which would exacerbate any flooding, and 1 to 2 inches along I-95. Given how dry it has been, that likely would result in only some nuisance and poor-drainage flooding.

However, the American model had the storm center heading into the Chesapeake Bay, which likely would increase rain amount for the Philadelphia region and the potential for flooding along the Delaware River. “That’s a concern as well,” Larson said.

On that track the heaviest rains would fall right over Philly, “which would be more than poor-drainage flooding.”

In the meantime, the probability that the forecast details are going to change even as the winds and rains get underway is near 100%.