166
FXUS61 KPHI 131737
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
137 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/...
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.

A cold front to our west on Monday will be slow to move eastward
and it looks like convection associated with it will impact our
region after 18Z. With tropical levels of moisture and light
winds aloft, torrential rainfall will be likely with afternoon
and evening thunderstorms. A Flash Flood Watch will be in effect
beginning at 18Z Monday for southeastern Pennsylvania and the
I-195 corridor in New Jersey. Severe potential in the form of
isolated water loaded downdrafts is possible especially from
the Delaware Valley westward.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
A cold front will approach our region from the west Monday
while slowing down and undergoing frontolysis. Very slowly, this
front makes its way through the region Monday into Tuesday
before eventually stalling over/near the region for the
remainder of the term. Diffluence will be present aloft on
Monday as this front approaches, which will help support
widespread convection. Upper ridging will begin to build in from
the south into Tuesday, which should work to suppress coverage
of convection somewhat despite the presence of the decaying
frontal boundary.

PoPs have increased slightly across the board for Tuesday to
around 40-60%. This is primarily due to a slightly slower
progression of the decaying frontal boundary, however as
previously mentioned, the ridge building in from the south
should work to suppress coverage of convection compared to
Monday. In any case, scattered showers and storms are probable
Tuesday afternoon and evening again, especially along and south
of where ever the frontal boundary ends up. PWats south of the
front will still be near 2", so locally heavy downpours will
remain possible. As with Monday, the severe thunderstorm threat
will be 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 THROUGH SUNDAY/...
The stationary frontal boundary looks to plague the region
before an approaching low pressure systems lifts it through as a
weak warm front Wednesday/Thursday. Thereafter, another cold
front approaches, looking to pass through sometime near/during
the weekend (e.g, late Friday/early Saturday). The upper ridge
will retreat southward some with time from the middle to end of
the week, yielding a west/northwest flow aloft and southwesterly
return flow ahead of the late week cold front.

Unfortunately, this synoptic pattern supports a continuation of
the showery and stormy summertime pattern. Chances for showers
and thunderstorms Wednesday/Thursday/Friday, mainly during the
afternoon and evening time frames with diurnal heating in place.
End of the week/weekend cold front will probably end up being a
focus for severe thunderstorm potential, but as of now, there
are no particular days that stand out among the others regard
severe or flash flood potential. PWats will remain high, so
heavy downpours will remain possible through the entire week.
The severe thunderstorm potentially will probably be more
mesoscale drive than synoptic, typical of July.

Another hazard to monitor will be the building heat and
humidity toward the middle and end of the week with the
southwesterly return flow. This won`t be a pattern for extreme
temperatures, however highs in the low 90s with high humidity
(dewpoints in the low to mid 70s) will result in heat indices
near 100 degrees Wednesday through Friday. The hottest day
currently appears to be Thursday, but this is subject to change
based on how the pattern and convection evolve.

&&

.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
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 thundertorms 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 Thursday...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 stay below Small Craft Advisory criteria
through Monday.

Outlook...

Monday night through Thursday...No marine headlines expected.
Winds generally remain 15 kt or less with seas around 2-4 feet.
Showers and thunderstorms are possible daily, primarily in the
late afternoon and evening hours, with the greatest probability
of showers and storms being on Monday.

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

&&

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

&&

$$

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