Bethlehem, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

255
FXUS61 KPHI 130737
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
337 AM EDT Sun Jul 13 2025

.SYNOPSIS...
An extended period of very warm, humid, and unsettled weather
conditions is expected for the upcoming week. A cold front
approaches the region today into Monday before slowly crossing
through later Monday into Tuesday. Thereafter, the front stalls
near/over the region before lifting back north as a warm front
later Wednesday into Thursday. Another cold front approaches
towards the end of week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today looks mostly like a repeat of yesterday as easterly flow
continues to dominate. This means more low clouds and patchy fog
to start, with sun breaking through towards midday/early
afternoon. Also it means that convection will be mostly confined
to well inland/higher terrain locales, with I-95 and points
southeast seeing just slight chance of a shower or storm. Highs
well into the 80s with heat indices in the 90s.

Tonight, things start to change as a front approaches. Better
chance that some weakening convection from the west reaches our
western lower elevation zones than the last few days during the
evening, then remnant showers may cross the entire area
overnight. Otherwise, looks like another round of low
clouds/patchy fog by late at night. Lows mostly near or above
70.

&&

.SHORT TERM /MONDAY 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.

Some spotty showers leftover from tonight could linger for
areas during the Monday morning time frame, depending on the
timing of frontal movement. The main show will be a round of
widespread showers and thunderstorms expected for the region
Monday afternoon into the nighttime period, as the front only
sags ever so sightly to the southeast with time. PoPs for the
inland areas are around 50-80%, and lower toward the coast where
instability and forcing will be more limited.

As for the convective environment details, we will have a
tropical setup with tall, skinny CAPE profiles and low shear.
Low to mid level wind fields will be quite light, only around
10-15 kts at most, so deep layer shear will be low. This will
support a disorganized, pulsy nature to convection, which will
be influenced by meso to microscale factors such as terrain and
outflow boundaries. With PWats on the order of 2.0-2.5" across
the entire area and SBCAPE near 1500-2500 J/kg, we should see
scattered tropical downpours with frequent lightning developing
into the afternoon and evening. Given the weak flow, low shear,
and low DCAPE, severe thunderstorms are unlikely. However, an
isolated damaging wind gust cannot be ruled out due to water
loaded downdrafts and weakened tree root systems.

WPC has increased the Excessive Rainfall Outlook to a Slight
Risk for much of southeast PA, Philly metro and adjacent NJ
areas, and portions of Delmarva. This will be the area with the
greatest risk for heavy rainfall leading to flash flooding,
especially considering recent localized heavy rainfall events. A
Flood Watch will need to be considered in a future update, but
details on timing, convective evolution, and rainfall amounts
remain a little unclear at the moment.

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 SATURDAY/...
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 /08Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Thru 12Z...Low clouds developing generally with most areas
seeing cigs drop to IFR or lower. The set up looks more
favorable for low clouds than fog, except near the coast,
including KACY, where both the lowest ceilings and lowest
visibilities are likely to occur. By 09Z, expect most locations
to have IFR conditions. Winds remain light (5 kt or less),
generally favoring the southeasterly direction, but could be
variable at times. High confidence in overall pattern, low
confidence in timing/placement of development of fog and
visibility restrictions.

Today...Once low clouds and fog dissipate, will see a return to
VFR conditions. Storms will begin to approach the area from the
northwest by 00Z, but impacts mostly confined to KRDG/KABE.
Moderate confidence,

Tonight...VFR with a few t-storms near KRDG/KABE to start, then
cigs drop to IFR again most terminals. A few showers could make
their way across the rest of the terminals after 6Z. Low
confidence.

Outlook...

Monday 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 tonight.

Outlook...

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