450 FXUS61 KPHI 130715 AFDPHIArea Forecast Discussion National Weather Service Mount Holly NJ 315 AM EDT Sat Sep 13 2025
.SYNOPSIS... High pressure will be in control through tonight. A decaying cold front will approach late Sunday. High pressure returns on Monday and Tuesday. A coastal low may develop off the Southeast US while slowly drifting northeast on Wednesday and Thursday. High pressure arrives again on Friday.
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.NEAR TERM /THROUGH TONIGHT/... A relatively quiet morning is ongoing, though some radiational fog is starting to develop, mainly within the higher elevations and the coastal plain. Fog will gradually expand in coverage through the morning but mix out not long after daybreak.
For today, high pressure over the Mid-Atlantic is in control, bringing a nice day. Highs will get into the upper 70s/low 80s with some diurnal cumulus development leading to mostly sunny to partly cloudy skies. Not much else of note, just a nice mid-September Saturday.
For tonight, relatively similar conditions expected, though a shortwave sliding through will bring some more upper level cloud cover. This should limit fog development, but areas that stay mostly clear overnight (coastal plain of NJ and Delmarva) could see patchy fog develop yet again. Overnight lows drop into the upper 50s/low 60s.
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.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... A late summer warm and humid airmass will be in place during the short term period. Aloft, an blocking pattern will set-up through Monday as surface high pressure largely remains in control with the exception of a weak boundary passing through on Sunday night.
Mostly sunny skies, seasonably warm temperatures and muggy conditions will be on the table for Sunday. Highs will reach into the low to mid 80s with dew points in the upper 50s to low 60s. While this won`t feel like the peak of summer heat, it`ll definitely be more noticeable compared to the weather we have encountered over the past several weeks. A cold front will approach from the northwest late in the day, but will be decaying as it nears our area. Shouldn`t observe anything in terms of precipitation as most forecast guidance lacks any moisture and skies remain mostly clear. So, other than a wind shift on Sunday night associated with the boundary, nothing out of the ordinary is expected. Lows will be seasonable in the mid 50s to low 60s.
For Monday, there will be a lack of cold and dry air behind the front with high pressure setting back up over New England. This will result in the relatively muggy airmass to linger into Monday as onshore flow recommences. Highs should be perhaps a degree or two lower than Sunday under partly cloudy skies. Tranquil weather will continue into Monday night, other than an increase in clouds with lows remaining near seasonable levels.
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.LONG TERM /TUESDAY THROUGH FRIDAY/... The blocking pattern aloft will continue through much of the long term period as upper level ridge will extend across the Great Lakes region as a cut-off upper level low will meander over the Southeast US / Mid-Atlantic region through Thursday. At the surface, high pressure will largely dominate much of the Mid-Atlantic, with potentially a coastal low developing off the coast of North Carolina around mid-week.
With the expected pattern set-up for mid-late week, should see more in the way of cloudy weather with the chance for showers returning to much of the area. Onshore flow should persist for much of the week as surface high pressure remains to our north and east. The greatest likelihood of precipitation will be further south and east, especially over the Delmarva where PoPs up to 40-50% are possible through mid-week. Further north and west, PoPs up to 20-30% are possible. The period with the highest threat for rain chances appear to be Wednesday night into Thursday as the potential coastal low makes its closest pass to the area. Any precipitation should remain rather light in nature, so not expecting a washout by any means. This system should depart the region by Thursday night giving way to the return of high pressure and clearer weather to end the week.
In terms of temperatures for the period, highs will likely remain a touch below normal, whereas lows will likely be a touch above normal thanks to the abundance of cloud cover expected through the period. All in all, close to average temperatures are expected.
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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 through most of the night though patchy fog develops over the coastal plain late, potentially bringing conditions down as low as IFR to KACY/KMIV. Lower chances for fog at other terminals, down around 10-20% probability, so left any fog out everywhere else. Low confidence in timing and extent in any restrictions. Winds light/variable.
Today...Locally sub-VFR conditions possible early morning due to some low clouds/fog, otherwise VFR. Any fog mixes out by 12z. Winds generally out of the southwest around 5-7 kt or so, going more southerly later in the day. Moderate confidence.
Tonight...Primarily VFR. Some patchy fog bringing MVFR/IFR restrictions cannot be ruled out, mainly for KACY/KMIV. Winds generally light less than 5 kt, favoring a southerly direction. Low confidence.
Outlook...
Sunday through Monday night...VFR expected during the day, with sub- VFR conditions with FG/BR possible at night.
Tuesday through Wednesday...Primarily VFR expected with sub-VFR conditions possible at times. A chance for rain showers beginning Tuesday night into Wednesday.
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.MARINE... No marine headlines expected through tonight. East/northeast winds become more southeasterly this afternoon into tonight, around 10 kt or less. Seas 2 to 3 feet.
Outlook...
Sunday through Tuesday...No marine headlines expected. Fair weather.
Tuesday night through Wednesday...SCA conditions possible due to seas near 5 feet. Rain showers possible.
Rip Currents...
For Saturday, northeast to eventually southeast winds later in the day increasing to 10-15 mph. Breaking waves in the surf zone of 2-3 feet with an easterly swell around 8 seconds are forecast. As a result, there is a MODERATE risk for development of dangerous rip currents at all beaches.
For Sunday, south to southeast winds around 10-15 mph throughout the day. Breaking waves in the surf zone of 2-3 feet with an easterly swell around 8 seconds are forecast. As a result, there is a MODERATE risk for development of dangerous rip currents at all beaches.
For specific beach forecasts, visit weather.gov/beach/phi
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.PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None.
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SYNOPSIS...DeSilva NEAR TERM...Hoeflich SHORT TERM...DeSilva LONG TERM...DeSilva AVIATION...DeSilva/Hoeflich MARINE...DeSilva/Hoeflich
NWS PHI Office Area Forecast Discussion