519
FXUS61 KPHI 071731
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
131 PM EDT Mon Jul 7 2025

.SYNOPSIS...
Bermuda high pressure will remain in place offshore through the
week. Chantal`s remnants will pass offshore of Delmarva this
evening, then a few additional weak systems and a slow moving
frontal boundary will impact the region through the remainder of
the week. This will result unsettled conditions, with daily
chances for showers and thunderstorms through much of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
A Flood Watch has been issued for the potential for flash flood
across portions of the forecast area this afternoon.

The well advertised tropical airmass has pushed into the region
as the CIRA Advected PW plots show that the deep moisture plume
is currently moving across New Jersey this morning. HIRES
guidance is still struggling this morning dealing with the
convection as the HRRR is about 3 hours late on the DelMarVa
showers. Given the struggle overnight last night and the current
underperforming of guidance, I anticipate were still on track to
see the potential for flash flooding later today.

The surge of moisture is expected to continue through the
morning as the remnants of Chantal move into the region this
afternoon. HREF LPMM guidance highlights the potential for
DelMarVa and portions of central Jersey to see as much as 5+
inches of rain this afternoon. With PWATs forecast to be above
the 90th percentile of climo, warm cloud depths quite high,
light steering flow, and favourable upper level jet dynamics the
potential for flash flooding is concerning. Hires guidance has
been under performing on the convection from Chantal this
morning across NC leading to the concern that guidance may even
be underdone with respect to qpf totals for our areas. For the
reasons mentioned above, WPC has also increase the ERO potential
to a SLGT risk for flash flooding.

With the increase in humidity and cloud cover, temps will be a
few degrees cooler than yesterday however heat index values will
be much higher with apparent temps getting close to 100 for the
urban corridor this afternoon.

Heading towards the evening hours, we`ll see an upper level
trough start to dig into the region shunting the remnants of
Chantal offshore. The surface front wont actually reach the area
until Tuesday but it should act to bring the rain threat to an
end this evening by around 10pm. The net impact will be another
evening of overnight lows in the low to mid 70s in very muggy
conditions.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Unsettled and active weather with tropical humidity will
persist Tuesday through Wednesday. Tuesday still has the
greatest potential for the most widespread showers and
thunderstorms, although Wednesday will also see scattered
showers and thunderstorms developing again. The showers and
thunderstorms will be capable of producing locally heavy
rainfall that could lead to flash flooding. The threat for
flooding could be exacerbated by multiple rounds of rainfall
over multiple consecutive days. There will also be a risk of
locally damaging wind gusts with any stronger storms both days.
Details follow below.

Shortwave troughing will settle across the upper Midwest and
Great Lakes regions Tuesday then slowly push closer toward the
east coast through Wednesday night. This combined with a broad
jet streak downstream will place our region locally in a
persistent region of broad upper diffluence, which will be
favorable for supporting multiple rounds of convection. At the
surface, high pressure will be located offshore with south to
southwest flow persisting through the period. The remnants of
Chantal will be offshore by Tuesday, however its tropical
environmental conditions will linger Tuesday and Wednesday
thanks to the persistent warm/moist advection sourced from the
Gulf. A slowly moving frontal boundary will settle into the area
late Tuesday, then linger through Wednesday. This could act as
a focusing mechanism for convection leading to flooding and
severe threats.

Tuesday and Wednesday will feature similar convective
environments, although coverage of convection is anticipated to
be greater on Tuesday. Cloud cover on Wednesday should help
suppress coverage of convection somewhat, especially toward the
north of where ever the subtle frontal boundary stalls out.
PWats in the 1.8-2.3" range; tall, skinny CAPE on the order of
1500-3000 J/kg; and relatively low unidirectional effective
shear near 15-20 kts could support training convection where any
surface boundaries are in place. There won`t be much dry air to
speak of for increased DCAPE, however steep low level lapse
rates combined with water loaded downdrafts will yield a
localized damaging wind threat with any stronger or more
organized cells.

So to summarize, a marginal severe environment, but more
concerning is the heavy rainfall and flash flooding threat this
setup will present. We`ll continue to monitor this potential
closely in the coming forecast updates, but the main take away
here is that we`re growing concerned about the potential impacts
of multiple consecutive days of locally heavy rainfall and
maringal severe risks. It will be a busy and active stretch of
weather ahead this week.

As for temperatures, Tuesday will be the hottest day of the
short term period and hottest day of the entire week ahead with
forecast high temperatures in the upper 80s to mid 90s in most
areas. Dewpoints will be in the low to mid 70s, resulting in
heat indices in the mid 90s (north) to mid 100s (south). Given
the forecast and increasing confidence for heat indices around
100 degrees for the urban corridor and adjacent areas of central
New Jersey and southeastern Pennsylvania, we`ve gone ahead with
a Heat Advisory to highlight this threat for Tuesday. This
advisory could need to be expanded south into far southern New
Jersey and Delmarva (where criteria is 105 degrees) if
confidence increases for heat indices near 105 degrees to occur.

Wednesday will experience similarly oppressive humidity,
especially south of the frontal boundary, however the cloud
cover and coverage of convection should moderate temperatures
compared to Tuesday with highs in the mid to upper 80s for most
areas. The should keep heat indices below advisory criteria,
however it will still be quite muggy and tropical feeling out
there. Low temperatures will be in the upper 60s to mid 70s both
nights and humid.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The early week troughing to our west will push into our region
and linger nearby to close out the week Thursday and Friday.
This should yield below normal temperatures, though still with
high humidity, and a continuation of daily chances of showers
and thunderstorms. There is greater uncertainty regarding any
impacts and threats from this activity though. At the surface, a
backdoor cold front could push into the area as surface ridging
tries to build across coastal New England Thursday, and
especially by Friday. However, a lack of any real dry air
advection will still leave humid and moist conditions in place
during this period.

Ultimately, this pattern will still support scattered showers
and some thunderstorm potential, but details on any impacts
remain unclear. What we do know is that temperatures will
moderate some, with high temperatures in the upper 70s to mid
80s in most areas and lows in the 60s to low 70s.

Even greater uncertainty for the forecast into next weekend as
guidance begins to diverge significantly in solutions. Stuck
with the NBM given the uncertainty, which includes chances of
convection each day. However, confidence in this period is very
low.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Today...VFR conditions expected for the remainder of
the afternoon. Showers and isolated thunderstorms expected
mainly between 19Z-00Z for all terminals, included in TEMPO
groups. VSBY/CIGS restrictions down to MVFR possible. Souhterly
winds around 10 kt, with gusts up to 20 kt at KMIV/KACY.
Moderate confidence.

Tonight...Primarily VFR. Scattered mid-high clouds with a few
low clouds possible. Southwest winds around 3-5 kt, becoming
VRB/calm at times. High confidence.

Tuesday...VFR expected for much of the day with sub-VFR
conditions possible late in the afternoon as scattered
thunderstorms move into the region after 19Z. Southwest winds
around 5-10 kt with gusts up to 15 kt possible. Moderate
confidence.

Outlook...

Tuesday night through Friday...VFR should generally prevail
during the daytime periods with daily chances for thunderstorms,
especially in the afternoon and evening hours. Areas of fog and
low clouds with restrictions more probable at night.

&&

.MARINE...
No marine headlines in effect though this evening. Winds
generally southerly 15-20 kt with seas increasing to 3-4 feet.
Isolated showers and thunderstorms will be in an around the
Delaware Bay during the morning and afternoon with the showers
and thunderstorms eventually dragging east over the Atlantic
waters this evening. Locally strong winds and seas will be
possible in and around any thunderstorms. Winds and seas should
be sub SCA criteria heading into the overnight hours.

Outlook...

Tuesday through Friday...Winds and seas are forecast to remain
below advisory criteria. Daily chances of showers and
thunderstorms. Some areas of fog possible at times.

Rip Currents...

For today, southerly winds will increase to 10-15 mph. Breaking
wave heights increase to 3-4 feet with a primary SE swell
around 1-3 feet and an 8 second period increasing to around
12-14 seconds during the afternoon. With the winds looking more
onshore, have opted to increase the rip current risk to HIGH for
dangerous rip currents from Cape May to LBI. Will maintain
MODERATE for the easterly facing beaches across Delaware and
Monmouth in NJ.

For Tuesday, winds shift southwesterly becoming more alongshore
flow around 5-10 mph in the morning increasing to 10-15mph in
the afternoon. Breaking wave heights should be in the 2-4 foot
range depending on beach orientation with a primary SE swell
increasing to 4 feet at a 6-8 second period. Given the tides
will be around low tide in the morning with the increase in
swell, will maintain a HIGH risk for rip currents for the
easterly facing beaches and MODERATE elsewhere.

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

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

&&

.HYDROLOGY...
A Flood watch is in effect for Monday. A tropical airmass with
precipitable waters in excess of 2" will persist over the
region today. Slow moving steering flow and a tropical moisture
will lead to highly efficient rainfall across the region. Basin
wide rainfall totals are anticipated to be in the 1 to 2 inch
range with the potential for up to 5 inches in heavier
thunderstorms. Main stem river flooding is not anticipated but
flash flooding of smaller streams/creeks and areas of poor
drainage will be possible. Please heed any road closures and law
enforcement instructions in case of flooding.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 10 PM EDT this evening for PAZ070-071-
     101>106.
     Heat Advisory from 10 AM to 8 PM EDT Tuesday for PAZ070-071-
     101>106.
NJ...Flood Watch until 10 PM EDT this evening for NJZ009-010-012-
     013-015>019-021.
     Heat Advisory from 10 AM to 8 PM EDT Tuesday for NJZ009-010-
     012>023-027.
     High Risk for Rip Currents until 8 PM EDT this evening for
     NJZ024>026.
DE...Flood Watch until 10 PM EDT this evening for DEZ001>003.
     Heat Advisory from 10 AM to 8 PM EDT Tuesday for DEZ001>003.
MD...Flood Watch until 10 PM EDT this evening for MDZ012-015-019-
     020.
     Heat Advisory from 10 AM to 8 PM EDT Tuesday for MDZ012-015-
     019-020.
MARINE...None.

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...Deal/DeSilva
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...Deal/DeSilva/Staarmann
MARINE...Deal/Staarmann
HYDROLOGY...PHI