647
FXUS61 KPHI 152324
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
724 PM EDT Sat Aug 15 2026

.WHAT HAS CHANGED...
Increased confidence in two distinct rounds of showers and
thunderstorms tomorrow into tomorrow night. Increasing confidence
in a cold front crossing through the region Thursday into
Friday.

Updated the aviation section for the 00Z TAFs.

&&

.KEY MESSAGES...
1. High pressure builds offshore of New England tonight ahead
of an approaching frontal system that will move across the area
Sunday and Sunday night.

2. Rainy conditions Sunday into Sunday night with heavy
rainfall possible.

3. A trailing mid level short wave trough may result in another
round of showers and thunderstorms Monday Afternoon and Evening.

4. A cold front is expected to cross through the region Thursday
into Friday.

&&

.DISCUSSION...
KEY MESSAGE 1 ...High pressure builds offshore of New England
tonight ahead of an approaching frontal system that will move
across the area Sunday and Sunday night.

One more night of fair weather tonight as high pressure builds
offshore of New England tonight ahead of an approaching frontal
system. After dewpoints drop during the day today, they will creep
up again tonight into Sunday morning.

KEY MESSAGE 2...Rainy conditions Sunday into Sunday night with
heavy rainfall possible.

A warm front will lift into the region during the day Sunday, but
likely not make it past central/southern portions of Delmarva and
southern New Jersey, before a cold front and triple point low
approach the area late in the overnight. We expect a couple of
rounds of precipitation as these systems move into the area. The
first will begin late morning into the afternoon hours as a short
wave/vorticity impulse approaches from the west. This round will
likely be mostly showers with no thunder activity as we will be
north of the warm front and instability will be minimal to non
existent. Rainfall with this first batch will likely be mostly 0.25-
0.50 inches or less area-wide.

The next batch is expected to move into the area during the evening
and overnight hours as the second short wave/vorticity impulse moves
into the area ahead of the approaching cold front and possible
triple point low. PWATS continue to increase to 2-2.25 inches, so
there will remain the threat for heavy rainfall as this rainfall
moves across the area. It looks like the heavy rainfall will be
fairly progressive, so we are not planning on a Flash Flood Watch at
this time. However, there will may still be some localized flash
flooding if any training does occur, especially in urbanized and
poor drainage areas as 1-2 inches of rain, with locally higher
amounts, will be possible overnight

There is still not a lot of instability since we`ll still be north
of the warm front, so thunderstorms are not expected to be
widespread. They still can`t be ruled out however, and any severe
threat looks to be across portions of southern New Jersey and
central/southern portions of Delmarva which will be closer to the
warm front.

KEY MESSAGE 3...A trailing mid level short wave trough and weak cold
front may result in another round of showers and thunderstorms
Monday Afternoon and Evening.

The cold front associated with the low that approaches the region on
Sunday will finally progress through the region and move offshore
on Monday. Additionally, in the the mid-levels, a trailing
short wave trough will cross overhead. The net result is that
isolated to scattered showers and thunderstorms will be possible
during the day on Monday.

As for hazards, this round appears to have very limited threats for
both flash flooding and severe hazards. Convection on Monday will be
much more weakly forced (as compared to Sunday/Sunday Night), and
bulk shear values are depicted in the 20 to 25 kt range, which is
rather modest. This limits the severe threat. Model soundings depict
still relatively high precipitable water values, and warm cloud
layers above 10K ft, which results in some heavy rain threat.
However, with limited shear and coverage of convection, the threat
for any one area to get heavy rain for long enough to result in
flash flooding remains low.

For those hoping for a significant cool down in the wake of this
cold front, unfortunately the temperature gradient is very small. As
such highs on Tuesday will be at or just a degree or two lower than
Monday. That being said, the front should usher in drier air, so
regardless it should feel more comfortable on Tuesday.

KEY MESSAGE 4...A cold front is expected to cross through the region
Thursday into Friday.

The next main focus is another cold front arriving in the region
during the Thursday into Friday time period. There are some big
timing differences between models on when exactly the front will
arrive and when the mid level trough will cross offshore. As
such, there is considerable uncertainty with the potential
hazards as the severe and hydro threats will be dependent on
the prime time for any showers and thunderstorms.

In terms of temperatures, so far this appears to be a stronger cold
front than the early week cold front. As such, temperatures going
into the weekend should be around 5 degrees lower compared to
the midweek time period.

&&

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

Tonight...VFR conditions expected. Winds become more out of the
southeast overnight at 5 knots or less with periods of light and
variable.

Sunday...VFR conditions to start Sunday morning. By mid-morning
through the afternoon, ceilings lower to MVFR from west to
east with showers moving in. Winds remain out of the southeast
and increase to around 10 knots with gusts upwards of 20 knots
by the evening hours.

Sunday night...MVFR or IFR conditions expected with a period of
moderate to heavy showers during the evening and overnight hours.
Isolated thunderstorms are possible. South to southeast winds at
around 10 knots with gusts of 20 knots.

Outlook...

Monday...Isolated showers and thunderstorms may result in temporary
visibility and ceiling restrictions.

Tuesday and Wednesday...VFR conditions expected.

Thursday...Sub-VFR possible with the chance for showers and
thunderstorms.

&&

.MARINE...
Rest of today-Tonight...Conditions will remain below advisory levels
through tonight.

Sunday-Sunday night...Winds and seas are expected to increase to
advisory levels Sunday afternoon and continue through Sunday night.
Isolated thunderstorms are possible as well, mainly for Delaware Bay
and the Atlantic Ocean waters adjacent to Delaware and southern New
Jersey.

Outlook...

Monday through Wednesday...Once seas subside below 5 ft Monday
morning, winds and seas should stay below SCA criteria.

Wednesday night into Thursday...A brief period of SCA conditions are
possible Wednesday night into Thursday morning mainly due to
elevated seas. However, the latest models have trended down on wave
heights.

Rip Currents...

Sunday, southeast winds in the morning will turn south at 10 to
20 mph with gusts up to 25 mph during the afternoon. Breaking
waves will increase to 2 to 3 feet. There will be multiple swell
groups, but the dominant swell is expected to be onshore with a
period of 8- 9 seconds. With that said, all swell groups look
to be around a foot or less, so winds and breaking wave heights
will be the primary driver of rip current risk. With these
factors considered, have opted for a MODERATE risk for the
development of dangerous rip currents for the Jersey Shore from
Ocean County southward, and a LOW risk for Monmouth County
portions of the Jersey Shore and all Delaware beaches where
winds will be more shore-parallel.

Monday, southwest winds in the morning at 10-20 mph with gusts
near 25 mph will turn west in the afternoon and decrease to 5-10
mph. Breaking waves will decrease to 1 to 3 feet. Dominant
southeasterly swell around 3 feet with a period of 6-7 seconds.
For now have opted for a LOW risk for the development of
dangerous rip currents for all area beaches. If the timing of
the wind shift or decrease in wave heights is delayed from the
current forecast, certain areas could need upgrades in future
updates.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 2 PM Sunday to 4 AM EDT Monday for
     ANZ430-431.
     Small Craft Advisory from 4 PM Sunday to 11 AM EDT Monday for
     ANZ450>455.

&&

$$

DISCUSSION...Guzzo/Johnson/MPS/Robertson
AVIATION...Guzzo/Johnson/Robertson
MARINE...Cooper/Johnson/Robertson