212
FXUS61 KPHI 060956
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
556 AM EDT Sun Jul 6 2025

.SYNOPSIS...
High pressure will begin to retreat offshore today, resulting
in increasing humidity. Bermuda high pressure will then remain
in place through the upcoming week. Chantal`s remnants will pass
to our south late Monday, then a few additional weak systems
will impact the region through the remainder of the week. This
will result in temperatures near to a few degrees above normal,
high humidity, and unsettled conditions, with daily chances for
showers and thunderstorms through much of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure has largely drifted offshore as southerly return
flow has setup across the region. This will continue to advect
in both warmer temperatures and more noticeably, humidity
through the morning. Highs today will be largely in the upper
80s to low 90s as a result. Significant moisture will also begin
to surge into the region with Tropical Storm Chantal moving
into the Carolinas. The main effect will be increasing dew
points. Lingering subsidence from the departing high should keep
most of the region dry but with the increase in surface
moisture, several high res members are suggesting that some
isolated afternoon convection will trigger across Delmarva.

The more tropical airmass continues to push in during the
overnight Sunday night into Monday morning with dew points
creeping into the low 70s. This will keep lows tonight above
average in the low to mid 70s across the region.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Turning unsettled with tropical humidity into the new week.
Monday and Tuesday both have a threat of scattered to numerous
thunderstorms with locally heavy rainfall that could lead to
flash flooding. There will also be a risk of locally damaging
wind gusts with any stronger storms.

Broad ridging across the region will retreat offshore into
Monday as shortwave troughing develops across the upper Midwest
and Great Lakes regions. This shortwave trough will eject
eastward to our north by late Tuesday. At the surface, high
pressure will be located offshore with return flow ramping up
through Monday as tropical cyclone Chantal`s remnants dissipate
across the Carolinas and southern Virginia. The remnants are
anticipated to slide offshore to our south late Monday. While we
are not expecting any direct impacts from Chantal`s remnants,
its presence very nearby will result in the tropical environment
that will be in place driving our locally heavy rainfall
threat. This setup will result in a slight warming trend in
temperatures, and a more significant increase in dewpoints and
humidity by Monday and Tuesday.

By Monday, an upper jet streak to our northeast will place our
region in a weak diffluence regime aloft. Thus with the
increasing humidity and diurnally driven instability, we should
experience scattered convection developing by midday. The
convective environment won`t be particularly favorable for
severe thunderstorms, however a few isolated severe storms
cannot be ruled out. Vertical shear is relatively weak, only
around 10-20 kts or so, and the instability profile is tall,
skinny CAPE on the order of 2000 J/kg. PWats will be on the rise
too, with the latest guidance indicating values ranging from
2.0-2.5" across much of the area. So a decidedly tropical
environment with light flow could result in some locally heavy
rainfall amounts and localized flash flood threat in addition to
the water loaded downdrafts and localized severe threat. We`ve
added a mention of heavy rain to the forecast generally
following where the Day 2 ERO Marginal Risk is outlined.

High temperatures will be similar to Sunday in the upper 80s to
low 90s, however dewpoints and humidity will be noticeably
higher compared to Sunday. This will result in heat indices in
the mid to upper 90s in most inland areas. Cloud cover will also
be noticeably increased compared to the weekend. Warm and muggy
conditions remaining at night with lows in the 70 to 75 degree
range.

Tuesday`s convective environment will be similar to Monday`s,
although coverage of convection is anticipated to be greater
than Monday given the forcing aloft. PWats in the 1.8-2.3"
range; tall, skinny CAPE on the order of 2000-3000 J/kg; and
relatively low unidirectional shear near 15-20 kts could support
training convection where any surface boundaries are in place.
So again, a marginal severe environment, but perhaps more
concerning is the heavy rainfall and flooding threat this setup
will present. We`ll continue to monitor this potential closely
in the coming days.

With the continued southwest flow, Tuesday should be a few
degrees warmer than Monday, but this will depend on cloud cover
and convection in the area. The temperature forecast has
increased a degree or two across the board, which will out heat
indices closer to Heat Advisory criteria, especially in the
urban corridor.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Troughing will remain across the Great Lakes Wednesday, which
will approach closer to our area Thursday and/or Friday. This
should result in the greatest chances for showers and storms
occurring Thursday and Friday, although broad diffluence aloft
will also support scattered convection on Wednesday as well.

Wednesday should see less coverage of convection given the more
pronounced shortwave trough pushing offshore late Tuesday, but
some isolated to scattered storms will certainly remain
possible. The next system approaching from the west by Thursday
and Friday will then yield greater chances for storms to close
out the week, but details on this remain unclear at the moment.

Expect temperatures to remain near to slightly above normal
with high humidity levels through the middle of the week. Highs
in the mid 80s to low 90s and lows in the mid 60s to mid 70s.
Weak low pressure developing to our west with the late week
shortwave should result in some onshore flow late in the week,
which should tend to moderate temperatures a bit. We could even
see a back door front Friday, which would moderate temperatures
even more.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...VFR. Light and variable wind becoming south-southwest
and increasing to 5-10 kt during the afternoon. High confidence.

Tonight...Sub-VFR developing as cigs lower to low MVFR or IFR.
South to southwesterly flow generally around 10kts or less.
Moderate Confidence.

Monday...MVFR/IFR ceilings gradually lift however showers and
thunderstorms will be possible around the terminals. Moderate
Confidence.

Outlook...

Monday through Thursday...Prevailing VFR with daily chances for
thunderstorms, especially in the afternoon and evening hours.
Areas of fog possible at night.

&&

.MARINE...
No marine headlines are in effect through Sunday night. Winds
mainly out of the south-southwest around 5-10 knots through
tonight, increasing to around 10-15 knots during the day today
with a few gusts up to 20 kts possible. Seas of 2-3 feet with
fair weather anticipated across the NJ Atlantic waters while
some afternoon convection may make it to the Delaware Bay this
afternoon.

Outlook...

Monday through Thursday...Wind and seas are forecast to remain
below advisory criteria. Daily chances of showers and
thunderstorms, otherwise fair weather.

Rip Currents...

For today, southerly winds will remain 5-10 mph. Breaking wave
heights of 1-2 feet with a primary SE swell around 2 feet and a
6-8 second period. There do appear to be some longer period
swells setting up at 44009 this morning, with obs showing the
dominant period as of 3am around 16 seconds. However the
dominate swell is between 1.5-2 feet so we`ll opt to stay with
LOW for dangerous rip currents for all beaches today.

For Monday, southerly winds will increase to 10-15 mph.
Breaking wave heights increase to 2-3 feet with a primary S
swell around 3 feet and a 6-8 second period. Given slightly
stronger winds and slightly higher waves with slightly higher
swell, went with MODERATE at the more southerly facing NJ
beaches of Cape May, Atlantic and Ocean, and LOW for the
easterly facing beaches of Monmouth and DE.

Rip currents occur often in the vicinities of jetties and piers
and the speed of the currents are generally maximized at low
tides.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...Deal
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...Deal/Staarmann
MARINE...Deal/Staarmann