798
FXUS61 KPHI 092259
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
659 PM EDT Sun Aug 9 2026

.WHAT HAS CHANGED...
Aviation section updated for the 00Z TAFs.

Updated Rip Current forecast for Monday and Tuesday.

&&

.KEY MESSAGES...
1. Daily chances for showers and thunderstorms will return
Monday and into the middle of the week. There is a risk for
strong to severe thunderstorms during the week, as well as a
marginal risk for localized heavy rainfall leading to flash
flooding.

2. Hot and humid conditions will persist into the middle of the
week, but humidity will not be as oppressive as recent days.

&&

.DISCUSSION...
KEY MESSAGE 1...Daily chances for showers and thunderstorms
will return Monday and into the middle of the week. There is a
risk for strong to severe thunderstorms during the week, as well
as a marginal risk for localized heavy rainfall leading to
flash flooding.

A mid-level shortwave trough will approach the area Monday
afternoon into the evening as mean flow shifts more westerly and
mid-level flow increases amid falling heights. The timing of
this synoptic evolution has continued to be a bit earlier with
the recent guidance for Monday. This mid-level shortwave trough
will be moving in from the west which means it will initiate
showers and thunderstorms off to our west Monday morning.
Currently, model guidance decays this activity before it reaches
our area and keeps it off to the west. Monday`s convection
potential will at least partially depend on what occurs upstream
of our area through the day.

For this update, SPC has maintained the Marginal (level 1 out
of 5) Risk for severe thunderstorms for much of our forecast
area for Monday. The Slight (level 2 out of 5) Risk was expanded
east today right to our forecast area border. There remains
uncertainty around Monday, but an additional expansion further
east into our forecast area is possible if trends continue to
hold. Given the recent trends among CAM guidance and model
soundings, the primary risk is damaging wind gusts as there
looks to be more of an upscale growth potential into a line
segment as the activity approaches our area. Instability and
low-level lapse rates are supportive of severe weather along
with increasing bulk shear values for storm organization.
Another note, there could also be a non-zero tornado threat as
well as model guidance shows low- level shear increasing during
the afternoon and evening. However, there remains a bit of
uncertainty around how some of thermodynamics evolve through
Monday afternoon and evening.

In terms of flash flooding, there is a Marginal (level 1 out 4)
Risk for excessive rainfall for areas mainly near and northwest
of the I- 95 corridor. PWATs do look to increase again to
upwards of 2 inches, so there is the heavy rain potential.
However, with a more linear storm mode being possible, this will
lead to a more progressive storm motion as the mid-level flow
increases Monday. One takeaway with this forecast update is
there remains uncertainty around the timing of the convection.
Variations remain among model guidance and what happens for our
forecast area will also depend on what happens upstream to our
north and west with that convective development.

Recent forecast trends have resulted in lower instability
compared to previous runs on Tuesday given the faster evolution
of the synoptic features (cold front and shortwave trough).
Essentially, it looks like Tuesday`s activity will be shunted to
our southwest compared to previous forecasts based on the
latest synoptic trends. With that said, we could still see some
convection potential or even get the remnants of whatever occurs
upstream later in the evening. So while the threat of severe
storms now appears to be lessening for Tuesday, we could still
get showers and storms in some form. Details for Tuesday are
even more uncertain than Monday, and Monday`s activity will
probably play some role in what exactly happens Tuesday.

A cold front looks to stall to our northwest Tuesday into
Wednesday. Multiple waves look to ride along the stalled
boundary which will support diurnally driven convection
continuing at least through Thursday. The front looks to push
through by late Thursday and a much drier and cooler airmass
will arrive by Friday and Saturday as a result, which will bring
us a more pronounced break in convective potential and more
pleasant weather conditions.


KEY MESSAGE 2...Hot and humid conditions will persist into the
middle of the week, but humidity will not be as oppressive as recent
days.

A relatively stagnant synoptic pattern will remain in place across
our region. Quasi zonal mid and upper level flow will be in place
through the middle of the week as Bermuda high pressure persists
offshore. This will keep a very warm and moist airmass in place
across the region through the period.

Hot and humid conditions will continue for the next several days. A
weak cold front passing through the area today will continue to
usher in slightly drier air and allow dewpoints to mix out some
during the afternoon hours both today and Monday. This will give
some slight reprieve from the excessive humidity we`ve experienced
in recent days, though highs will still be in the upper 80s to low
or even mid 90s. The lower dewpoints will result in maximum heat
indices mainly in the mid to upper 90s, though could get near 100
degrees in Delmarva and near the coast in New Jersey. Since the
forecast is decidedly below criteria, we have opted to continue
without a new Heat Advisory, though it will still be hot and humid.

The faster synoptic pattern evolution described in the first section
above has resulted in a slightly lower forecast for temperatures and
heat index values for Tuesday. High temperatures in the mid 80s to
low 90s for most, and heat index values are now forecast to peak
below Heat Advisory criteria. Though the front looks to stall to
the northwest, west to northwest flow aloft will allow for a
continued reduction in temperatures into Wednesday and Thursday.
Highs Wednesday and Thursday are mostly in the mid to upper
80s, which will be closer to average for early to mid August.

By Friday and Saturday with the front finally having pushed
through, a much drier and cooler airmass will arrive, which will
bring much more pleasant weather conditions. Dewpoints may drop
into the 50s again for many areas with highs forecast to be in
the low to mid 80s.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. LGT/VRB to nearly calm winds. High confidence.

Monday...Overall VFR. Chances for TSRA after 18Z with brief
MVFR or lower conds. W-SW winds 5 to 10 kt. Moderate confidence.

Monday night...Lingering MVFR or lower conds in TSRA in the
evening, then VFR. W winds 5 to 10 kt. Moderate confidence.

Outlook...

Tuesday-Thursday...Prevailing VFR, except restrictions possible
with afternoon/evening showers and thunderstorms.

Friday...VFR. No significant weather expected.

&&

.MARINE...
No prevailing marine hazards through tonight. An isolated
shower/storm possible along the sea and/or bay breeze, which
could briefly impact the back bays or nearshore waters. South to
southwest winds generally around 10-20 kt with seas around 2-4
feet. Aside from the isolated shower/storm potential, fair
weather expected.

For tonight, winds become more west to southwest at 5-10 kt with
seas of 2-3 feet. On Monday, winds increase to 10-20 kt out of
the south to southwest with seas of 2-3 feet. Thunderstorms are
possible during the afternoon and evening hours on Monday.

Outlook...

Tuesday through Friday...No prevailing marine hazards expected.
Thunderstorms possible each afternoon and evening through
Thursday.

Rip Currents...

For Monday...Light winds in the morning will increase and settle
out of the south-southwest around 10 to 20 mph in the afternoon.
Breaking wave heights of 1 to 2 feet are expected with multiple
swell groups and periods, generally ranging around 5 to 7
seconds. Given these conditions, have opted to continue with a
LOW risk for the development of dangerous rip currents at all
beaches.

For Tuesday...Light winds in the morning will settle out of the
west-southwest in the afternoon between 5 to 15 mph. Breaking
wave heights will remain around 1 to 2 feet with a southerly 2
foot swell around 5 to 7 seconds. With little changes in overall
conditions, will go with a LOW risk for dangerous rip currents
at all beaches.

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

&&

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

&&

$$

DISCUSSION...AKL/Guzzo/Staarmann
AVIATION...AKL/Guzzo/MPS
MARINE...AKL/DeSilva/Guzzo