833 FXUS61 KPHI 060636 AFDPHIArea Forecast Discussion National Weather Service Mount Holly NJ 236 AM EDT Sat Sep 6 2025
.SYNOPSIS... High pressure offshore dominates most of today, then a strong cold front approaches this afternoon and crosses the region tonight. This front will become nearly stationary over New Jersey and Delmarva through Sunday, and weak low pressure may track on this boundary Sunday afternoon. The front departs Sunday night as high pressure builds in from the west for the start of the new week. Low pressure may track along the coast on Wednesday. A cold front will then cross the region Thursday into Friday.
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.NEAR TERM /THROUGH TONIGHT/... Scattered strong to severe thunderstorms are expected this afternoon and evening, with damaging wind gusts as the primary threat. Some urban and poor drainage flooding is possible as well.
A relatively quiet morning is ongoing, and that will generally remain the case as a cold front currently over western Pennsylvania is modestly progressing towards our area, and will be the focus for the development of showers and thunderstorms in the afternoon and evening. Some patchy fog is possible this morning as well, though mainly in valleys and more rural and sheltered regions.
As the front and incoming shortwave aloft get closer this afternoon, coverage of showers and thunderstorms quickly increases as we get towards the PM hours. Ahead of the front, skies will be mostly sunny to partly cloudy, allowing for destabilization. Temperatures get into mid to upper 80s along and south/east of the I-95 corridor, with lower temperatures north and west as the front moving in during the afternoon will limit heating. With ample instability ahead of the front, and 0-6 km bulk shear around 30-40 kt, sufficient conditions exist for clusters of storms (and perhaps a few supercells) to quickly develop in the afternoon. Convection starts to fire around noon in the Lehigh Valley and Poconos and slowly pushes east, getting to the I-95 corridor by the mid to late afternoon. Storms continue to push east and should be at the coast by the late afternoon/early evening. While the severe threat diminishes quickly after 8 PM, some backbuilding and anafrontal precipitation could result in scattered showers and pockets of heavier rain hanging around through the first half of the night. Conditions slowly improve as the night goes on and drier air works in behind the departing front.
Overall, the main threat will be damaging wind gusts through the afternoon and evening. No real changes to the convective outlook with a SLIGHT (2/5) Risk in effect for the I-95 area and surrounding suburbs. Towards the outer western edges of the CWA in the Poconos and Lehigh Valley, a MARGINAL (1/5) risk is in place as the front coming in earlier in the day may limit the severe potential. The front coming in later near the coast and across southern Delmarva will also reduce some of the risk for damaging winds, where a MRGL risk is in place.
In addition to the severe threat, there is a threat for some flash flooding. Main area to watch will be the urban corridor as rainfall rates over 1" per hour are certainly possible with the heaviest storms. SLIGHT (2/4) risk is in place for excessive rainfall for the I-95 corridor, with a MARGINAL (1/4) elsewhere. Rainfall amounts generally around 0.5-1" with locally higher amounts likely. Highest chance to see higher amounts will be from the I-95 corridor on east.
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.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... The cold front will be hung up over coastal New Jersey and down into Delmarva. Some weak low pressure may track along this front, keeping showers in the forecast, mainly for Delmarva and New Jersey, into Sunday afternoon, and then showers taper off by sunset. It will be much cooler on Sunday. Clouds and showers will keep temperatures in the 60s to around 70 for New Jersey and Delaware, while highs will get into the low to mid 70s in southeast Pennsylvania and the eastern shores of Maryland.
Skies clear out Sunday night. Turning much cooler with lows in the upper 40s in the southern Poconos, Lehigh Valley, and northern New Jersey, and in the low to mid 50s elsewhere.
Sunny and mild on Monday with highs in the 70s, and then lows Monday night will be similar to Sunday night.
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.LONG TERM /TUESDAY THROUGH FRIDAY/... High pressure builds in from the west, and the center of the high will pass north of the area Tuesday. Low pressure develops over the Southeast, and clouds associated with this low will build to the north. While Tuesday will start out mostly sunny, skies become partly to mostly cloudy late in the day. Mild with highs in the low to mid 70s.
Low pressure then tracks along the coast, but mostly offshore. This looks to bring scattered showers, mainly over Delaware and New Jersey, Tuesday night through Wednesday night. This will keep temperatures cooler along the coast as compared to southeast Pennsylvania, with highs generally in the low to mid 70s.
Weak high pressure builds trough the region Wednesday night through Thursday morning. Another cold front crosses the region Thursday night through Friday, but at this time, it looks to be a dry frontal passage. Turning warmer on Thursday with highs in the upper 70s to lower 80s, then cooler on Friday with highs in the low to mid 70s.
Generally followed the NBM during this time.
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.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.
Through 12z...VFR. Southerly winds around 5 kt. Slight chance of patchy fog (15-20%) but did not include restrictions at any terminal. Moderate confidence.
Today...VFR bulk of day, but intervals of sub-VFR increasingly likely later in the day as showers and storms develop, some of which could produce strong wind gusts. Outside of storms, winds generally southwesterly around 10 kts, with a few gusts up to 20 kts possible ahead of developing storms. Included VCTS at all TAF sites for portions of the afternoon and evening. Moderate confidence.
Tonight...Some shower activity lingers through the first half of the night resulting in MVFR/IFR restrictions, primarily for the I-95 and South Jersey terminals. An improvement to VFR is possible late. Winds become northwesterly right around 00z, and stay around 5-10 kt through the night. Low confidence.
Outlook...
Sunday...Lingering sub-VFR conditions, mainly at KMIV/KACY, in stratus/SHRA. Improving conditions otherwise.
Sunday night through Tuesday...VFR. NSW.
Tuesday night through Wednesday...Generally VFR, but sub-VFR conditions possible at KMIV/KACY in SHRA.
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.MARINE... No marine headlines expected through the morning. Southerly winds around 10-20 kt with seas 2 to 4 feet.
For this afternoon, a Small Craft Advisory is in effect for coastal zones north of Cape Henlopen as southerly winds increase to 20 to 25 kt. Lower winds expected south of Cape Henlopen and within Delaware Bay as gusts remain around 20 kt. Thunderstorms possible on the Delaware Bay after 18z and the ocean after 21z may result in some Special Marine Warnings being issued.
For tonight, winds diminish as a cold front comes through, bringing winds out of the northwest around 10-20 kt. Seas 2 to 4 feet. Scattered showers and thunderstorms expected on the water through most of the night.
Outlook...
Sunday through Monday night...Sub-SCA conditions. N winds generally 10 to 15 kt, turning E Monday night.
Tuesday through Wednesday...SCA conditions possible. E winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 feet.
Rip Currents...
Saturday...Southerly onshore/shore parallel winds on Saturday will be 15-20 mph by the afternoon. Wave period is 6-7 seconds but could be down to 4-5 seconds by the late afternoon as wind driven waves become more dominant. Breaking wave heights of 2-3 feet are forecast for the beaches of New Jersey. As a result, a MODERATE risk for the development of rip currents is forecast for all NJ beaches. For the Delaware Beaches, winds will be more shore parallel/slightly offshore. Breaking waves of 1-2 feet are forecast and as a result a LOW risk for the development of rip currents is forecast for the Delaware Beaches.
Sunday...Winds turn offshore on Sunday which should decrease the risk for the development of rip currents. Breaking waves look to be around 1-2 feet with a 6-8 second period. Therefore, a LOW risk for the development of rip currents is forecast for all beaches on Sunday.
For specific beach forecasts, visit weather.gov/beach/phi
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.TIDES/COASTAL FLOODING... Some spotty minor tidal flooding was observed with the high tide last night and more of the same is expected tonight and perhaps Saturday Night within the upper Delaware Bay, tidal Delaware River, and northeastern shore of Chesapeake Bay. Not expecting the need for Coastal Flood Advisories at this point, but some standing water may be seen in low lying areas within these communities near tidal areas.
No tidal flooding is expected along the Atlantic Ocean front.
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.PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from noon today to 6 PM EDT this evening for ANZ450>454.
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SYNOPSIS...MPS NEAR TERM...Hoeflich SHORT TERM...MPS LONG TERM...MPS AVIATION...Hoeflich/MPS MARINE...Hoeflich/MPS TIDES/COASTAL FLOODING...
NWS PHI Office Area Forecast Discussion