489 FXUS61 KPHI 170546 AFDPHIArea Forecast Discussion National Weather Service Mount Holly NJ 146 AM EDT Wed Sep 17 2025
.SYNOPSIS... A surface low located near the Mid-Atlantic coast today will track slowly northeastward towards the area through Wednesday night, brining unsettled weather. Thursday and beyond, the low is expected to track northeast away from the area while weakening. A cold front will move through the area on Friday, with strong high pressure in its wake remaining in control through the weekend and into early next week.
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.NEAR TERM /THROUGH TODAY/... High pressure centered over the Province of Quebec north of New York State will slide towards the Canadian Maritimes overnight and then will move offshore and over the western Atlantic Ocean on Wednesday. Meanwhile, low pressure off the Virginia/North Carolina Coast will slowly retrograde inland and northward overnight through Wednesday, where it will meander.
Waves of showers will continue overnight and into Wednesday, especially for the southern half of the area during the morning hours.
The highest QPF will be over Delmarva and southern New Jersey up to the I-95 corridor, where 1/2 inch to 1 inch of rain will fall during this time. North and west of the I-95 corridor, up to 1/4 inch of rain is expected.
A tight pressure gradient will form between the two systems. East to north winds will range from 10 to 20 mph north and west of the I-95 corridor, and from 15 to 25 mph with gusts up to 35 mph south and east of the I-95 corridor, with the strongest winds right along the coast.
Some shortwave energy may provide enough instability to trigger a couple of thunderstorms, some of which could result in locally heavy downpours with enhanced rainfall in those areas, and brief wind gusts as high as 45 mph. Best chances for convection will be over Delmarva, southern New Jersey, and the Delaware Valley.
Lows tonight will generally be in the upper 50s to low 60s and highs on Wednesday will be in the upper 60s to low 70s, though possibly as warm as the mid 70s in southern Delmarva.
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.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... By Wednesday night, the coastal low will be weakening substantially to the southwest of the area. It will continue to move east to northeast away from the area while weakening into Thursday afternoon. Lingering showers are expected Wednesday night, primarily across southeastern portions of NJ and the eastern Delmarva. A few isolated showers are possible across the rest of the area as well, but coverage will be much less widespread. With low clouds and showers, low temperatures will generally be in the low 60s. Across the Poconos and into far northern NJ, some clearing is possible, which would allow temperatures to drop into the mid-upper 50s.
Any remaining showers will depart the area by Thursday afternoon, with cloud cover decreasing from northwest to southeast throughout the day. Afternoon highs look to be in the mid-upper 70s. Thursday night, under partly to mostly clear skies, slightly cooler temperatures are expected, ranging from the mid-upper 50s across eastern PA and northern NJ to the low 60s across southeastern PA, southern NJ, and the Delmarva.
Friday looks to be a nice, warm day across the area. Under mostly clear skies, temperatures should rise into the low 80s for most locations. A cold front will begin to approach from the northwest, and depending on timing, it is possible that it could limit warming across northern parts of the area if it moves in a little faster than currently anticipated. The cold front will move through the entire area through Friday night. No precipitation is expected, but this front will usher in cooler temperatures. Lows Friday night will generally be in the mid- upper 50s, with upper 40s across the Poconos and far northern NJ.
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.LONG TERM /SATURDAY THROUGH TUESDAY/... After the passage of Friday`s cold front, strong high pressure centered over portions of Ontario, Quebec, and northern New England will shift southeast into the area. This will lead to comfortable temperatures with benign weather through the weekend, with a slow warming trend. Saturday and Sunday should feature high temperatures in the low-mid 70s areawide, with lows generally in the mid 50s.
Monday and Tuesday look to be slightly warmer, with highs in the mid- upper 70s and lows in the upper 50s to lower 60s. Low pressure off the East Coast will approach the area Monday into Monday night, this will lead to some increase in cloud cover and perhaps a shower or two along the immediate coast, but that should be the extent of the impacts.
It continues to look like the upper-pattern will become slightly more unsettled towards Tuesday and beyond, but for now it looks like any more active weather will hold off until just beyond the forecast timeframe.
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.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.
Through 12Z...Conditions lower to MVFR/IFR throughout in low clouds and showers, though conditions may not lower to sub-VFR at KRDG/KABE until daybreak. Guidance has slightly delayed lower CIGs overspreading the region. The MVFR stratus deck should arrive at the I-95 corridor by 08z. Generally MVFR conditions, with some IFR possible at MIV/ACY. NE winds 5 to 10 kt at KRDG/KABE, and 10 to 15 kt with gusts up to 20 kt elsewhere. Winds 15 to 20 kt with gusts around 25 kt possible at KMIV/KACY. A few embedded thunderstorms may impact KMIV/KACY. Moderate confidence.
Wednesday...Primarily MVFR with periods of showers. THunder is possible, but chances are too low to include a TAF mention at this time. Showers may cause visibility and ceilings may drop to IFR at times. Winds east/northeast around 10-15 kts with gusts near 20 kts. Moderate confidence.
Wednesday Night...Primarily IFR with low clouds, scattered showers, and patchy fog. NNE winds 5-10 kt. Low confidence.
Outlook...
Thursday...Conditions should improve through Thursday, but lingering periods of sub- VFR conditions can`t be ruled out.
Thursday night through Sunday...VFR. No significant weather.
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.MARINE... A coastal low will affect the waters tonight through at least Wednesday.
The Gale Warning was extend through 4 AM for coastal waters south of Great Egg Inlet and for lower Delaware Bay as coastal mesonet sites and buoys continue to report Gale Force gusts.
East to northeast winds 15 to 25 kt with 35 kt gusts where the Gale Warnings are in effect and gusts up to 30 kt elsewhere. Seas 6 to 10 feet will subside to 5 to 8 feet overnight, and then to 4 to 6 feet on Wednesday.
Visibility restrictions in showers and fog. A few embedded thunderstorms may affect the waters tonight through Wednesday.
Outlook...
Wednesday night through Friday night...Winds and seas are expected to have diminished below SCA criteria by Wednesday night, and should remain so through Friday night. No marine headlines are expected.
Saturday through Saturday night...A period of enhanced northerly winds and elevated seas are possible behind a cold front. Currently, it appears that winds should remain below 25 kt and seas below 5 feet, but this will need to be monitored as it gets closer in time.
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 10 AM EDT this morning for ANZ430. Gale Warning until 4 AM EDT early this morning for ANZ431- 453>455. Small Craft Advisory until midnight EDT tonight for ANZ450>452.
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SYNOPSIS...Cooper NEAR TERM...Hoeflich/MPS/Staarmann SHORT TERM...Cooper LONG TERM...Cooper AVIATION...Cooper/Hoeflich/MPS/Staarmann MARINE...Cooper/Hoeflich/MPS/Staarmann TIDES/COASTAL FLOODING...Cooper
NWS PHI Office Area Forecast Discussion