774 FXUS61 KPHI 170758 AFDPHIArea Forecast Discussion National Weather Service Mount Holly NJ 358 AM EDT Wed Sep 17 2025
.SYNOPSIS... A coastal low located over the mouth of the Chesapeake will remain nearly stationary today while weakening before tracking slowly northeastward off the coast by Thursday. A cold front will pass through the area on Friday, followed by strong high pressure which will be in control through the weekend and into early next week.
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.NEAR TERM /THROUGH TONIGHT/... A weakening coastal storm will linger across our region into tonight. This will result in cloudy skies, below normal temperatures, continuing northeast to east winds, and periods of showers for much of the day. The winds and showers will lessen into tonight with lingering low clouds and some fog possible.
A broad, closed upper trough will deamplify and open, eventually ejecting northeast into tonight. At the surface, weakening high pressure across New England will gradually push toward the Canadian Maritimes. Meanwhile, the coastal low will remain in the vicinity of our region while weakening, then eventually shift offshore into tonight.
Bands of showers will continue to impact the region today, generally moving inland and gradually lifting toward the north as the day progresses. The greatest chances of rain (60-80%) will be mainly along and south of I-78. The rain will be showery in nature, not really an "all day rain" type of situation, rather periods of light to moderate showers at times. Some elevated instability will be present, with MUCAPE values of a few hundred J/kg possible across the coastal plain especially. This could result in some thunder with an more robust convection that develops. No severe thunderstorms are expected, but the heavier showers or storms could help mix down briefly stronger wind gusts around 30 mph. Given the recent dryness and heavier rainfall occurring over the sandy coastal plain, no fresh water flood threat is expected.
QPF is around 0.5-1" of rain for the coastal plain southeast of I- 95. North and west of I-95, QPF is mainly 0.1-0.25" at most. The uncertainty lies in the middle right around the I-95 corridor, which should experience 0.25" or so, but some areas may see a little more or less than that.
Northeast winds will be near 10-20 mph through much of the day, with gusts near 25 mph possible. Temperatures will remain nearly steady in the upper 60s to low 70s. Lows tonight in the mid 50s to mid 60s. Low clouds will linger tonight and some fog development is possible. WInds will shift more northerly near 5-10 mph tonight.
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.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... By Thursday morning, the sub-tropical low will be nothing more than an open trough as it moves further out to sea. Some lingering showers may still occur near the coast in the morning, but overall should see drastic improvements for all areas by the afternoon with clearing skies. High temperatures will vary from the mid to upper 70s for coastal areas, with low to mid 80s across the I-95 corridor and points north and west. Clear skies and benign weather will continue into Thursday night where low temperatures are expected to fall into the mid 50s to low 60s.
Friday looks to be a pretty nice day overall with a brief return of summer-like temperatures. Highs are expected to top out in the low to mid 80s across the entire region, outside of the higher terrain which will be in the upper 70s. The is one feature to note though, which is a cold front that will approach the area from the north as the day progresses. Depending on forward progression of the front, areas north and west may end up a few degrees cooler than currently forecast. No precipitation is expected though as the atmospheric column lacks any moisture, so skies are anticipated to be mostly sunny on Friday. Behind the front though, there will be a strong push of cold air advection and drier air that will pour into the region by Friday night. This will lead to lows bottoming out in the 50s for most, 40s across the higher terrain and 60s near the coast.
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.LONG TERM /SATURDAY THROUGH TUESDAY/... The long term period for the weekend and into early next week will largely be dominated by strong high pressure originating from Canada. The center of this high will settle over Quebec on Saturday, shifting southeast into the Canadian Maritimes on Sunday, with ridging still extending west into the Mid-Atlantic into the beginning of next week. This will yield a very nice weekend overall, with mostly clear skies and light onshore flow.
By Monday and Tuesday, will begin to see southwesterly flow develop aloft as a deepening trough moves into the High Plains. While the area will still be under the influence of surface high pressure, we will begin to see a gradual warming trend and the return of above normal temperatures by the middle of the week. Will have to monitor a stalled boundary near the Carolina coast on Tuesday, which may result in a few isolated showers near the coast. However, the potential of this occurrence is low thanks to strong ridging remaining over much of the Mid-Atlantic.
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.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.
Through 12Z...Ceilings lowering to MVFR from south to north through daybreak. Some light to moderate showers may briefly cause MVFR visibility restrictions. NE winds around 10-15 kts with gusts near 20-25 kts possible from near I-95 and southeast to the coast. Moderate confidence on timing of MVFR restrictions.
Today..Generally prevailing low end MVFR ceilings, with IFR possible at times. Bands of showers will pass through the region, resulting in MVFR to IFR visibility at times. Some isolated thunderstorms possible, but probability is too low to include a TAF mention at this time. Some fog development is possible as well. NE winds 10-15 kts peaking this morning, then gradually lessening after 18Z. Gusts near 20-25 kts early, mainly from near I-95 and southeast toward the coast. Moderate confidence overall, but low confidence on the details outlined in the TAFs.
Tonight...IFR ceilings expected, with some improvement possible late. North to northeast winds near 5-10 kts. Low confidence.
Outlook...
Thursday...Lingering sub-VFR conditions expected in the morning with a chance of showers. All terminals should improve to VFR in the afternoon with clearing skies.
Thursday night through Sunday...VFR. No significant weather expected.
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.MARINE... The Gale Warning was extended until 7 AM, as gale force wind gusts continue within the warning area. These should gradually subside through daybreak. Elsewhere, a Small Craft Advisory is in effect through 2 PM for upper Delaware Bay and through midnight for the Atlantic coastal waters.
Northeast to east winds will gradually lessen through the remainder of the morning. Seas will also lessen through the remainder of the day, but will remain near 5 feet or more through midnight or so across the Atlantic coastal waters. Overnight, winds will shift northerly around 10-15 kts with seas continuing to diminish. Periods of showers and a few thunderstorms through this afternoon. Some fog may also cause some visibility restrictions at times.
Outlook...
Thursday through Friday...No marine headlines expected. Lingering showers expected on Thursday, otherwise fair weather.
Friday night through Saturday...SCA conditions possible mainly due to wind gusts up to 25 kt. Seas around 3-4 feet.
Saturday night through Sunday...No marine headlines expected. Fair weather.
Rip Currents...
For Wednesday, east-northeast winds around 10 to 15 mph with breaking waves of 3 to 5 feet. Easterly swell around 5 to 7 feet at 8 seconds. Given these factors, will maintain a HIGH risk for the development of dangerous rip currents at all beaches. The Rip Current Statement has been extended through 8 PM Wednesday due to this threat.
For Thursday, north-northeast wind around 10 mph. Breaking wave heights generally 2 to 3 feet. Easterly swell will subside some to 3-4 feet at around 8 seconds. Given the less favorable wind direction, decreasing breaking wave heights, and swell height, have elected to go with a MODERATE risk for the development of dangerous rip currents for all beaches.
For specific beach forecasts, visit weather.gov/beach/phi
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.TIDES/COASTAL FLOODING... Some minor tidal flooding was observed across the Delaware Bay and southern Delaware, though waters have receded as we get away from high tide and the Coastal Flood Advisory was allowed to expire. As the coastal low to the south weakens, and more northerly flow takes over, tidal levels should diminish and nothing more than spotty minor tidal flooding is expected along the southern NJ and Delaware coastline, with the Delaware Bay, and up the tidal Delaware River.
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.PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Risk for Rip Currents through this evening for NJZ014-024>026. DE...High Risk for Rip Currents through this evening for DEZ004. MD...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ430. Gale Warning until 7 AM EDT this morning for ANZ431-453>455. Small Craft Advisory until midnight EDT tonight for ANZ450>452.
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SYNOPSIS...DeSilva NEAR TERM...Staarmann SHORT TERM...Cooper/DeSilva LONG TERM...Cooper/DeSilva AVIATION...DeSilva/Staarmann MARINE...DeSilva/Staarmann TIDES/COASTAL FLOODING...PHI
NWS PHI Office Area Forecast Discussion