Flood advisory for Philly, Jersey Shore due to supermoon

A flood advisory is in place through Saturday for the Jersey Shore and along the Delaware River from the mouth of Delaware Bay to central Bucks County, and you can blame one of the astronomical highlights of the year for any inconvenience.

The moon, which approaches Earth and is knighted as a “supermoon” when it reaches fullness at 4:21 p.m. Friday, seven minutes before sunrise, has added an extra boost to water levels along the Atlantic coast and the Delaware tidewater, with help from onshore wind.

The flooding is expected to be at the “sunny day level” — a type that NOAA says has been increasing. The National Weather Service says that could result in “some partial or complete road closures.”

However, it is possible that some areas of Cape May County’s beach towns could experience more severe “moderate” flooding, said Lee Robertson, a senior meteorologist at the weather service office in Mount Holly.

What times can flooding be expected in Philly and on the coast?

The weather service advisory expects minor flooding around high tide times along the Delaware, Atlantic Ocean and Barnegat Bay.

High tide on the Delaware in Philly occurs at 1 p.m. Friday and Saturday. High tide at sea is at 6 both Friday and Saturday.

Along the shores of the bay, high tide will be Friday at 06.00 and 19.00 and Saturday at 7.00.

Robertson said he was putting air in his tires Wednesday night, deflated to say the least from the recent chill, when it dawned on him, “I don’t really need my flashlight.”

When the full moon is this close — it will be within 225,000 miles of Earth when it reaches that moment of fullness on Friday — it looks about 30% brighter than it does when it’s furthest away.

Plus it’s about as high in the sky as it gets: Its career is the mirror opposite of that of the Sun, which sinks ever lower on its way to the winter solstice.

This is the last supermoon of 2024, and it will still be 99% full when it rises at 17.04 on Saturday, and 96% at moonrise on Sunday at 17.57

A perhaps unfortunate byproduct of the show is that the proximity to Earth also adjoins that of the moon the force of gravity to pull the tide.

Global warming and nuisance flooding in Philly and on the coast

Global warming has also contributed to nuisance flooding, and a NOAA report published in 2022 said the Northeast experienced twice as many days of high-water flooding compared to 2000.

In part, that would be the result of rising water levels worldwide from rising global temperatures and melting glaciers.

When could the Philly region see flooding rains again?

That remains anyone’s guess.

New Jersey declared a drought warning Wednesday and called for voluntary water restrictions. Philadelphia and its neighboring counties are under a drought watch.

With its weekly update Thursday, the US Drought Monitor had nearly all of eastern Pennsylvania in “severe drought,” as did all of New Jersey, except for southeastern parts of the state, which were in “extreme drought.”

A rash of brush fires have broken out across the region, and the weather service says there are more possible Friday afternoon as humidity drops and winds pick up.

NOAA’s Climate Prediction Center sees the odds of normal precipitation for the period from Nov. 22 through Thanksgiving, and Robertson said rain is possible in the middle to late next week

But it’s going to take a deluge or two or three to wipe out the huge rainfall deficits in the region. Philly has received 8% of its normal rainfall in the past 60 days, according to the weather service’s Middle Atlantic River Forecast Center.

Robertson said he wouldn’t be shocked if Philly got two inches of snow before seeing two inches of rain. (But there is no snow in the forecast either.)

Staff writer Frank Kummer contributed to this article.