Wachovia Spectrum, Pennsylvania Weather Forecast Discussion

574
FXUS61 KPHI 202336
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
736 PM EDT Sat Sep 20 2025
.SYNOPSIS...
High pressure will be in control through Sunday before shifting
offshore on Monday. A warm front will pass through the region on
Monday as well, before a cold front gradually tracks through the
area on Wednesday. This front will then stall over the Mid-Atlantic
region through the end of the week into next weekend, causing a
period of unsettled weather.
&&
.NEAR TERM /THROUGH SUNDAY/...
Tonight, high pressure to the north will continue to influence
our weather with fair weather. Clouds will probably expand
across south NJ and Delmarva overnight as the onshore flow
causes low level humidity to increase. We will add more
cloudiness to the grids for these areas attm. Not expecting fog,
but probably more stratus at times. Low temps will remain mild
S/E with upper 50s to low 60s but cooler N/W with fewer clouds.
In theses N/W areas, low will favor the upper 40s to low 50s.
East winds 5 to 10 mph this evening then less than 5 mph
overnight.
On Sunday, the high pressure will remain across the offshore
waters of New England. A subtle shortwave moves across PA and up
into NY later during the afternoon. The east surface flow will
continue across our region resulting in varying amounts of low
clouds during the morning. these clouds should thin out and
bring a mostly sunny day across the region. There is some
possibility of low clouds remaining across the shore areas late
into the day however. Another pleasant day generally with highs
in the low/mid 70s expected. East winds increasing to around 10
mph.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Surface high pressure over New England will shift south of Nova
Scotia on Sunday night before moving further east into the North
Atlantic on Monday. Ridging from this high will continue to extend
into the Mid-Atlantic region though, so aside for a weak warm
frontal passage occurring on Monday, relatively benign weather is
expected through the short term period.
In terms of benign weather, mostly clear skies are expected for
Sunday night as high pressure remains in control. We`ll likely
encounter one more night of strong radiational cooling, where lows
will fall into the 40s/50s under light northerly flow. The pattern
does begin to change on Monday though as surface flow gradually
shifts to more southerly as a warm front passes to our north. This
will be the beginning of warm air advection regime as highs on
Monday will warm back into the mid to upper 70s to around 80 degrees
under mostly sunny skies. By Monday night, a shortwave to the west
will begin to approach the region leading to an increase in clouds
with a slight chance of a shower in the Poconos overnight. Temps
will be much milder compared to the night before with lows only in
the upper 50s to low 60s.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The long term period as a whole looks to be largely unsettled with
several opportunities for showers and storms. Starting out with
Tuesday, this may end up being one of the more active weather days
in the long term period as a cold front approaches. The region will
be located well within the warm sector as highs will top out in the
low to mid 80s with dew points in the mid to upper 60s. As we are
now within range of some of the CAMs and machine learning guidance,
there is indication of a pre-frontal advancing out ahead of actual
cold front, which may end up being the primary culprit for showers
and thunderstorms developing by the afternoon and evening. Too early
to tell if these storms may end up being severe, but can expect a
few locally strong storms possible given the overall environment.
Showers and storms will progress through the area on Tuesday night
before beginning to subside with the loss of diurnal heating. The
actual front then looks to cross through on Wednesday before the
front stalls south of the area by Wednesday night.
With the front remaining in close proximity to the area through the
end of the week and into next weekend, several opportunities for
additional showers and storms will be possible. However, there is
quite a bit of uncertainty with respect to the large scale weather
pattern into next weekend as deep upper level trough will dig into
the Deep South. There is quite a bit of variability amongst model
guidance in terms of whether this trough cuts off and meanders
around the Southeast US or not. So for now, have simply kept the NBM
output which carries a slight chance to a chance of showers and
thunderstorms for the Thursday through Saturday period. Temperatures
though look to be seasonable for late September.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.
Tonight...VFR, except MVFR CIGs at KRDG/KABE/KMIV/KACY. E to SE
winds less than 10 kt. Moderate confidence.
Sunday...MVFR CIGs at KMIV/KACY in the morning, then VFR. VFR
elsewhere. E to SE winds 5 to 10 kt. Moderate confidence.
Outlook...
Sunday night through Monday night...VFR. No significant weather
expected.
Tuesday through Thursday...Primarily VFR, with occasional periods of
sub-VFR conditions. A chance of showers and a slight chance of
thunderstorms possible with patchy fog/mist possible.
&&
.MARINE...
Will go ahead and cancel the Small Craft Advisory that was in
effect for lower Delaware Bay as wind gusts are less than 25 kt.
Otherwise, SCA flags will remain up across ANZ454 (between Cape
May NJ and Cape Henlopen DE) with gusts in the mid 20s kts
continuing. These gusts will subside tonight. SCA flags will
continue elsewhere (on the ocean) with seas reaching 5ft and
continuing into Sunday. Fair weather tonight and Sunday.
Outlook...
Sunday night through Monday...Lingering SCA conditions possible due
to seas around 5 feet. Fair weather outside of SCA conditions.
Monday night through Thursday...No marine headlines expected. Fair
weather expected for Monday night with showers and thunderstorms
possible for Tuesday through Thursday.
Rip Currents...
For Sunday, east-northeast winds are around 15 to 25 mph.
Breaking wave heights increase to around 3 to 4 feet. Slightly
larger easterly swell increasing to around 2 feet at 6-7 seconds
in length. Some wave guidance has a secondary long period (10
to 12 second) swell arriving tomorrow. With greater wave
heights, onshore flow, and multiple swell groups (one of which
being a long period swell), a HIGH risk of rip currents are in
effect for Sunday. Given that we are late in the season, and not
many beaches are guarded this time of year, please exercise
caution if at the beaches tomorrow.
For Monday, winds turn more southeasterly and be much lighter,
only around 10 MPH. The longer period swell remains with 2 to 4
foot breaking waves. Given lighter flow onshore and calmer
conditions, elected for a MODERATE risk for rip currents at all
beaches over a high risk.
For specific beach forecasts, visit weather.gov/beach/phi
&&
.TIDES/COASTAL FLOODING...
With multiple days of onshore flow, and a New Moon tomorrow,
some spotty minor tidal flooding is expected with tonight`s high
tide. Locations that could see some standing water in low lying
areas include the New Jersey and Delaware ocean coastline and
communities near Delaware Bay.
No tidal flooding is expected within the tidal Delaware River,
Raritan Bay, or Chesapeake Bay. Onshore flow weakens tomorrow,
with no further tidal flooding expected outside of tonight`s
high tide.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Risk for Rip Currents from Sunday morning through Sunday
     evening for NJZ014-024>026.
DE...High Risk for Rip Currents from Sunday morning through Sunday
     evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Sunday for ANZ450-454.
     Small Craft Advisory until 2 PM EDT Monday for ANZ451>453.
     Small Craft Advisory from 2 PM Sunday to 2 PM EDT Monday for
     ANZ454-455.
&&
$$
SYNOPSIS...DeSilva
NEAR TERM...MPS/OHara
SHORT TERM...DeSilva
LONG TERM...DeSilva/Guzzo
AVIATION...DeSilva/MPS/OHara
MARINE...DeSilva/Hoeflich/MPS/OHara
TIDES/COASTAL FLOODING...

NWS PHI Office Area Forecast Discussion