714
FXUS61 KPHI 101837
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
237 PM EDT Mon Aug 10 2026

.WHAT HAS CHANGED...
A severe thunderstorm watch has been issued for the entire CWA
until 9PM this evening.

&&

.KEY MESSAGES...
1. Daily chances for showers and thunderstorms will return
today and into the middle of the week. There is a risk for
strong to severe thunderstorms, 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.

3. There is potential for minor tidal flooding during the
evening high tides this week along the Atlantic coast, Delaware
Bay, and tidal Delaware River, especially on Tuesday and
Wednesday.

&&

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

A severe thunderstorm watch has been issued for the entire CWA
until 9PM this evening.

A mid-level shortwave trough is approaching the area as of the afternoon
and should transit through until the evening as mean flow shifts
more westerly and mid-level flow increases amid falling heights.
Model consensus suggest this will arrive right around peak
diurnal instability in the mid to late afternoon hours.

SPC has expanded the Slight Risk (level 2 out of 5) Risk for
severe thunderstorms farther east to include our entire region,
save for a small portion of southeastern Delaware. There remains
some uncertainty in exactly how convection will evolve this
afternoon, and thus which areas will be at greater risk for
severe storms, so we`ll have to monitor trends upstream closely
as the day progresses.

The primary risk with any thunderstorms today will be damaging
wind gusts, as there looks to be more of an upscale growth
potential into a line segment(s) as the activity approaches our
area. Instability of 2000-3000 J/kg and low-level lapse rates
upward of 8C/km are supportive of damaging wind gusts, and deep
layer shear in the 25-35 kt range will support organized
convection. The line of storms will likely be fairly fast
moving, say 40-50 mph, so this should be a quick hitting event.
The tornado threat, while still non-zero, will be very limited
as LCLs will be fairly high and low level shear is meager at
best. As for flash flooding, there is a Marginal (level 1 out
4) Risk for excessive rainfall for our entire area. PWATs do
look to increase again to upwards of 2 inches, so there is heavy
rain potential. However, with a quick moving linear storm mode
anticipated, this will limit the potential for flash flooding.

The trend for lower instability has continued for Tuesday given
the faster evolution of the synoptic features (cold front and
shortwave trough). Tuesday`s activity will be displaced to our
southwest. 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 lower 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. SPC expanded the Marginal Risk
(level 1 out of 5) farther northeast into the Philly metro area,
and the entire area remains in the Marginal Risk (level 1 out
of 4) for excessive rainfall.

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
Wednesday, and possible 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. This 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 into the middle of the
week, although slightly lower temperatures and dewpoints will
arrive for Wednesday. Dewpoints are anticipated to mix out into
the mid to upper 60s again this afternoon. 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 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 will continue to support slightly lower temperatures
and heat index values beginning Tuesday. High temperatures in
the mid 80s to low 90s degrees for most Tuesday through Thursday,
with heat indices mainly in the mid 80s to mid 90s. This is closer
to average for early to mid August.

By Friday and Saturday with the front finally having pushed through,
a much drier and more 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. Dewpoints look to start rebounding into the 60s again
by Sunday.


KEY MESSAGE 3...There is potential for minor tidal flooding
during the evening high tides this week along the Atlantic
coast, Delaware Bay, and tidal Delaware River, especially on
Tuesday and Wednesday.

As we approach the New Moon on Wednesday, astronomical tides for
the evening high tide cycles will increase to around a half foot
below minor flood stage in many areas this week along the
Atlantic coasts of New Jersey and Delware, Delaware Bay, and
the tidal Delaware River. With tide departures running around a
half foot above average, this will raise a threat of minor flood
stage being reached for these areas.

We will continue to monitor the tide departures in the coming
total water level forecasts. Coastal Flood Advisories may be
needed for a few zones if the departures become high enough,
but at least spotty minor tidal flooding should be anticipated
around the times of the evening high tides this week. The
highest astronomical tides will occur on Wednesday, though
Tuesday`s tides are of similar height. The threat of minor tidal
flooding may linger through Thursday or Friday as well.

Tidal flooding is not currently forecast for the Eastern Shore
of Chesapeake Bay.

&&

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

Rest of Today...Prevailing VFR. Chances for TSRA after 19Z with
brief restrictions possible. Southwest to west winds increasing
to near 10 kts by 19Z or so. High confidence in prevailing
conditions, low confidence on timing of thunderstorms.

Tonight...Prevailing VFR conditions. Any thunderstorms ending
prior to 02Z. Southwest winds 5-10 kts shifting west to
northwest after 06Z. High confidence in prevailing conditions.

Outlook...

Tuesday-Thursday... Prevailing VFR. Restrictions possible with
afternoon/evening showers and thunderstorms.

Friday-Saturday... VFR. No significant weather expected.

&&

.MARINE...
No prevailing marine hazards through tonight. Winds south to
southwest around 5-15 kts, increasing to 10-20 kts during the
afternoon. Seas 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 Friday.

Rip Currents...

For Today...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/po
AVIATION...AKL/Staarmann/po
MARINE...DeSilva/Staarmann/po