082
FXUS61 KPHI 131846
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
246 PM EDT Sun Jul 13 2025

.SYNOPSIS...
Very warm and humid air will be over the region this week. A
cold front will move eastward into the region late Monday, and
then become stationary in our area on Tuesday and Wednesday. It
will move northward as a warm front on Thursday. Another cold
front approaches toward the end of week.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
The biggest concern through this period is the potential for heavy
rain and flash flooding, particularly with the storms late Monday
into Monday night.

Radar showing a north to south band of convection from the lower
Susquehanna Valley into the southern Poconos, grazing Berks and
Carbon counties. Latest hires guidance has convection moving
slowly eastward for the rest of the afternoon but it should
weaken by the time it reaches the Delaware Valley area by early
to mid evening.

With light winds and surface dew points in the lower 70s tonight,
low clouds and patchy fog will develop again. Best chance for
lower visibilities in fog are in southern New Jersey, the
Poconos, and Lehigh Valley.

On Monday, a front will approach the area at the surface at the
same time a short wave trough in the mid and upper levels
crosses our area. Models have trended slightly later with the
arrival of the front. Storms will happen well ahead of the
front, but it may mean especially for places like Delmarva and
South Jersey that storms are much later to arrive.

Heavy Rain/Flash flooding risk: More detail of the heavy
rain/flash flooding risk is below in the hydrology section.
However, this remains the main concern with any showers and
thunderstorms on Monday, particularly in the afternoon and
evening. There is enough of a risk that a flood watch for flash
flooding was issued for southeastern PA and in New Jersey from
the I-195 to I-80 corridors. Depending on what guidance depicts
with the 00Z model runs, the watch may need to be expanded to
include far NW NJ and the southern Poconos. To the southeast of
the watch (including Delmarva and South Jersey), given the
slightly later trend, not as confident that storms will be as
prolific rain producers by the time they reach those areas.

Other hazards: Aside from lightning, the only other risk to talk
about with the storms tomorrow is a small (5 to 15%) chance for
gusty winds. Overall, DCAPE values are very low, but there is
potential for precip loading to develop into a wet downburst
with stronger storms.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...

The previously mentioned front is expected to stall over our
region through mid week. A mid to upper level short wave ridge
will try to build in from the southwest, which could work to
suppress coverage of convection despite the presence of the
decaying frontal boundary. However, there is uncertainty in how
quickly this ridge will build east.

Scattered showers and storms are probable Tuesday and Wednesday,
primarily in the afternoon and evening, and especially along
and south of where ever the frontal boundary ends up.
Precipitable water values will remain well above average, so
locally heavy downpours will remain possible. At this point, the
risk for severe hazards is low.

Seasonable temperatures with humid conditions can be expected
through this period. High temperatures will be mainly in the mid
to upper 80s, with muggy nighttime low temperatures in the low
to mid 70s. Fog formation is possible for areas during the late
nighttime and early morning periods, but this will be dependent
on precipitation occurrence and mixing.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
This period will start off with a focus of dangerously hot
conditions, before another cold front approaches the region late
in the week.

Humid air will remain in place, and with continued southwesterly
flow (before the next cold front arrives), warm air advection
will continue. As such, heat index values near or above 100F
will be possible across most of the area (excluding higher
terrain in the Poconos and NW NJ) on Thursday. Depending on the
timing of the cold front, similar hot and muggy conditions could
continue on Friday.

This pattern supports a continuation of the showery and stormy
summertime pattern. Expect mostly diurnally driven
afternoon/evening showers and thunderstorms, that will be
limited in coverage. However, the next cold front will probably
end up being a focus for more widespread rain. As for severe
hazards, no strong signal either way; if the front comes in
during peak heating (which is unlikely at this point), then the
risk for severe storms could increase. Heavy downpours will
remain possible through the entire week. The severe thunderstorm
potentially will probably be more mesoscale drive than
synoptic, typical of July.

&&

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

This afternoon...MVFR ceilings becoming VFR. Thunderstorms
possible west of the Delaware valley. Light Southeast winds.

Tonight...Scattered thunderstorms this evening west of the
Delaware valley, otherwise VFR early. MVFR to IFR in low
ceilings after midnight. Light south wind.

Monday...VFR. MVFR in scattered afternoon thunderstorms. South
wind 5 to 10 knots.

Outlook...

Monday night through Friday...Overall, prevailing VFR
conditions. However, afternoon and evening SHRA/TSRA may result
in brief periods of sub-VFR conditions daily. Sub-VFR conditions
are also possible overnights/early mornings due to low clouds
and fog, but uncertainty remains on this potential, so
confidence is low.

&&

.MARINE...
Winds and seas should generally stay below Small Craft Advisory
criteria through Monday. gusty winds could be possible in the
vicinity of any thunderstorms late tomorrow.

Outlook...

Monday night through Thursday...Winds and seas should stay below
Small Craft Advisory criteria through this period. Showers and
thunderstorms are possible daily, primarily in the late
afternoon and evening hours.

Rip Currents...

Today, winds will be out of the east at around 10 mph with
breaking waves around 1 to 2 feet. This combined with a 2 foot
southeast swell every 7 seconds results in a LOW risk for the
development of dangerous and life threatening rip currents at
the Jersey Shore and at Delaware Beaches.

Monday, winds will be out of the south at around 10 mph with
breaking waves around 1 to 2 feet. This combined with a 2 foot
southeast swell every 6 seconds results in a LOW risk for the
development of dangerous and life threatening rip currents at
the Jersey Shore and at Delaware Beaches.

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...
As mentioned above, there is a risk for heavy rain leading to
flash flooding with any showers and storms Monday. A flood
watch for flash flooding was issued for southeastern
Pennsylvania, and the I-195 to I-80 corridor in New Jersey.

As mentioned by the previous shift, there are a lot of factors
that are increasing our risk for flash flooding. To start, the
pattern shows some similarities to the Maddox Synoptic Event
pattern, with the front becoming quasi stationary and limited
wind shear between the low and upper levels. Model soundings
indicate a tall, skinny CAPE profile typical of a heavy rain
pattern. Expect precipitable water values well above the 90th
percentile for this time of year, and possibly close to daily
records. Additionally, the warm cloud layer should be quite
deep, and storm motions, although slightly faster than what we
have seen Friday and Saturday, will still be less than 20mph.

The only factors not present that typically are with heavy rain
events is that wind shear will be weaker than typical (near or
below 10 kt), and there doesn`t look like there will be much of
a low level jet for moisture transport. This could limit how
long individual cells last before dissipating. Additionally,
confidence is lower than normal on the placement and amount of
precip given how poorly high resolution models have depicted the
showers and thunderstorms today.

At this point, the biggest concern is for flash flooding on
roadways, in urban areas, and for small streams and creeks.
What areas have flash flooding will be highly dependent on where
the heaviest downpours set up.

Significant main stem river flooding isn`t expected.


&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from Monday afternoon through Monday evening for
     PAZ060>062-070-071-101>106.
NJ...Flood Watch from Monday afternoon through Monday evening for
     NJZ007>010-012-015.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Franklin
NEAR TERM...Franklin/Johnson
SHORT TERM...Johnson/Staarmann
LONG TERM...Johnson/Staarmann
AVIATION...Franklin/Johnson/RCM
MARINE...Franklin/Johnson/RCM
HYDROLOGY...Johnson