Clouds and milder air roll into Philadelphia on Saturday morning, with temperatures starting out in the upper 50s. The calm start will not last long. A Coastal Flood Advisory is posted for the city and nearby counties for the high-tide window early Sunday, when onshore winds could push up to about a foot of water into the usual low-lying riverfront trouble spots. Higher-than-normal astronomical tides after Friday's New Moon are adding to the risk. Showers are expected late Saturday night into Sunday as a cold front swings through, and Sunday will feel noticeably cooler than Saturday. Boaters, shoreline residents and anyone traveling near the Delaware River should plan for ponding and possible temporary road closures around the high-tide cycle.
Timing And Rain
The main round of showers is expected late Saturday night into Sunday morning as a strong cold front crosses the region. According to the National Weather Service, the best chance for measurable rain comes overnight into the early hours of Sunday, although amounts look light, generally only a few hundredths to a few tenths of an inch. Behind the front, winds shift to the northwest and pull temperatures down across the area, trimming inland highs into the upper 50s to around 60. Low clouds and pockets of reduced visibility overnight could briefly complicate early Sunday commutes and flights.
Tides, Roadways And Boaters
The Coastal Flood Advisory calls for up to about one foot of inundation above ground level at the most vulnerable tide-prone locations during the early Sunday high tide. That is enough to cover low-lying roads and riverside walkways. A Small Craft Advisory is also in effect for coastal waters from 8 a.m. to 6 p.m. Sunday as winds shift and seas turn choppy for smaller vessels. Before heading to marinas or planning shoreline travel, check local tide gauges and forecast water levels through NOAA.
Colder Week Ahead
Colder air settles in behind the front. Highs on Monday and Tuesday drop into the 40s and 50s, and overnight lows take a sharp dip. Forecasters say widespread frost or even a freeze is likely early Tuesday morning, especially in suburban and inland areas away from the immediate river and coast, with some spots near or below freezing. If you already moved tender plants outside during the recent warm spell, it is time to cover them or bring them in before Monday night. Temperatures are expected to rebound later in the week as a southerly flow returns.
How To Prepare
If you live in low-lying riverside areas, move vehicles off the street and steer clear of driving through standing water. Mariners and small-craft operators should delay nonessential trips during Sunday’s advisory window, and gardeners should protect sensitive plants before Monday night. Keep devices charged and weather alerts enabled overnight so you can respond quickly if water begins to pond on local streets.
