567
FXUS61 KPHI 302042
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
442 PM EDT Mon Jun 30 2025

.SYNOPSIS...
The stalled front across the southern half of the region will
slowly return northward as a warm front through tonight
followed by a cold front later Tuesday. High pressure builds
closer later Wednesday into Thursday before settling over our
area on Friday and into the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Ongoing thunderstorms will continue to bring an isolated severe threat
for damaging wind gusts and localized flash flooding. The main
line of convection stretches across the I-195 corridor in New
Jersey into the Lehigh Valley and Poconos. This line continues
to slowly move northward towards an advancing warm front across
the I-80 corridor. Storms overall have been very slow-moving,
contributing to the localized flash flooding concerns.
Additionally, residual outflow boundaries have been resulting in
further convective development south of the main line of storms
where some backbuilding has been occurring as well. The current
forecast thinking is that these storms will persist through the
rest of the afternoon and into the early evening. This initial
round of storms is expected to diminish with the loss of daytime
heating, but a second, less impactful round of showers and
thunderstorms may arrive overnight as a weak shortwave trough
moves overhead tonight, providing weak forcing to help sustain
convection. This second round would carry a lower severe threat,
but still could see some localized flooding in areas already
soaked from the storms earlier in the afternoon. Second round of
convection may continue into early Wednesday morning, but there
remains a bit of uncertainty with that.

The silver-lining is that the rain-cooled air from the
afternoon storms have allowed us to cancel the Heat Advisory
that was previously in effect across the urban corridor. Lows
tonight will be in the upper 60s to upper 70s.

For Tuesday, with the warm front well north of the region and
the entire forecast area in the warm sector, another round of
severe thunderstorms and flash flooding is expected. In the
upper levels, an upper-level trough is forecast to shift
eastward and amplify some as it overspreads the Northeast and
Mid-Atlantic. This will drive a cold front across our region
later Tuesday.

In terms of the set-up for the second half of Tuesday, shear
will be more notable, around 30 kts of deep layer shear (0-6km).
Also, highs in the upper 80s to low 90s with dew points in the
low to mid 70s will provide an environment for growing
instability ahead of the cold front, with MUCAPE values likely reaching
3000J/kg. At this time, there is still some uncertainty on how
well the shear and areas of higher CAPE overlap along with the
timing of the cold front. Another uncertainty is the
possibility of morning convection. If lingering early morning
convection remains more widespread and takes longer to dissipate
and clouds linger longer, this will have impacts on how well we
destabilize before the cold front. Right now, the morning
activity looks to be done by the mid-morning hours of Tuesday
with enough time to get moderate instability. The latest severe
weather outlook continues with a Slight (2/5) risk for most of
our area with the remainder of the area (Poconos and coastal
strip) in a Marginal (1/5) risk. The primary threat will be
damaging wind gusts.

One other key impact point for Tuesday is a flash flooding threat.
Most of the area is in a Slight (2/4) Risk for excessive
rainfall with the Poconos and high elevations of northwest NJ in
a Marginal (1/4) Risk. PWAT values will rise
to 2-2.5 inches with warm cloud depth of 10-12 kft, so the
signal is there for the convection to be sufficient rainfall
producers. The good news is that the convection will be moving
but any training of showers or thunderstorms could lead to
increased concern for localized flash flooding. There is also a
signal for some frontogenetic forcing with the cold front which
could also enhance the precipitation rates with the convection.

While heat index values will be in the upper 90s Tuesday across
the Philly Metro, the criteria for a Heat Advisory changes on
July 1st to a heat index of 100 to 104 degrees for two
consecutive hours. A few locations near Philly may touch a 100
heat index, but it is not forecast to be widespread enough at
this time to warrant a heat advisory.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
The severe threat looks to come to an end around 00Z-03Z Wednesday,
but given the front slowing down Tuesday night, it is still near the
coastal areas by Wednesday morning. This will continue to lead to
the potential for lingering coverage of some showers or an isolated
rumble of thunder through Tuesday night into Wednesday morning. Lows
Tuesday night are in the mid 60s to low 70s.

Heading into Wednesday, our Tuesday cold front should be south and
east of our area by midday, and while temperatures do not look to
drop much, the dew points are forecast to lower some in the wake of
the cold front. Despite the presence of the upper-level trough, less
in the way of deeper moisture should keep the instability lower as
well. Given surface high pressure building closer to our area with
time, the chance for any showers and thunderstorms at this time is
little to none for the remainder of Wednesday into Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The upper level trough looks to become reinforced as it remains
across much of the Northeast through the end of the work week before
moving offshore over the weekend. At the surface, a high pressure
system continues to build in Thursday before settling over our area
on Friday and Saturday and moving offshore on Sunday.

While high pressure will be increasingly in control, a weak cold
front looks to sink southward during the afternoon and evening on
Thursday. This cold front looks to set off some showers and maybe an
isolated thunderstorm for areas near and NW of I-78. The remainder
of the forecast looks dry until Sunday when the high moves offshore.

Daytime temperatures in the 80s for most through Saturday, with
temperatures look to warm closer to 90 on Sunday. Dew points are
forecast to be in the low to mid 60s before increasing to around 70
on Sunday. Overall, the most pleasant day does look to be Friday
which should make for a nice forecast for the 4th of July.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of today...Mostly VFR, but ongoing scattered showers and
thunderstorms (40-60%) could bring periods of restrictions to
all terminals. Storms will be scattered, but slow-moving, thus
restrictions may last a bit longer than a standard thunderstorm
should there be one. Moderate confidence.

Tonight...Primarily VFR. Restrictions possible though with
scattered showers and thunderstorms (40-60%). Winds remaining
out of the south around 5-10 knots. Moderate confidence.

Tuesday...VFR to start. Restrictions likely with thunderstorms
in the afternoon (60-80%). Winds from the southwest around 10
kts gusting to 15 kts. Higher gusts possible in thunderstorms.
Moderate confidence.

Outlook...

Tuesday Night...Restrictions likely (40-60%) with showers and
thunderstorms moving through.

Wednesday through Saturday...VFR. No significant weather.

&&

.MARINE...
SCA conditions build overnight and into Tuesday. Seas 3-4 feet
tonight build to 3-5 feet early Tuesday morning across the
southern waters and spread north. Seas expected to be 4-6 feet
by Tuesday afternoon. South-southwest winds 15-20 kts tonight
build to 20-25 kts in the afternoon.

Outlook...

Tuesday night...SCA conditions continue through 06Z.

Wednesday into Saturday...Sub-SCA conditions expected.

Rip Currents...

Today, winds have become more onshore and will increase to around 10
knots by afternoon. The wave periods will remain around 8 to 9 sec.
with breaking waves around 2 to 3 feet. Thus, we`ll keep a MODERATE
risk for the development of dangerous rip currents for the NJ Shore
and  LOW risk for Delaware Beaches.

On Tuesday, winds turn more south-southwest and the period
will be around 7 seconds with breaking waves around 2 to 3
feet. Thus, we will continue with the MODERATE risk for the
development of dangerous rip currents for the NJ Shore and
LOW risk for Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 11 AM Tuesday to 2 AM EDT Wednesday
     for ANZ450.
     Small Craft Advisory from 5 AM Tuesday to 2 AM EDT Wednesday
     for ANZ451>455.

&&

$$

SYNOPSIS...AKL/Guzzo/Hoeflich
NEAR TERM...AKL/MJL
SHORT TERM...AKL/Guzzo
LONG TERM...AKL/Guzzo
AVIATION...Guzzo/MJL
MARINE...Guzzo/MJL