803
FXUS61 KPHI 130036
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
836 PM EDT Sat Sep 12 2026

.WHAT HAS CHANGED...
Aviation section updated for 00Z TAFs but no major changes to
the forecast.

&&

.KEY MESSAGES...
1. Low pressure lifting through the region tonight through Sunday
morning will produce showers and thunderstorms with the potential
for flash flooding across portions of the forecast area.

2. A cold front Thursday into Friday may bring some showers and
thunderstorms.

&&

.DISCUSSION...
KEY MESSAGE 1...Low pressure lifting through the region tonight
through Sunday morning will produce showers and thunderstorms with
the potential for flash flooding across portions of the forecast
area.

High pressure has moved offshore with a return flow beginning to
take shape across the area. As this continues to occur, low level
moisture will increase over the area. Meanwhile, low pressure will
organize and develop over the Mid-Atlantic. A warm front associated
with that low will lift north through the region later this evening
into the overnight , and then southerly flow will allow dew points
to rise well into the 60s and low 70s. PWATs will rise to 2-2.25
inches.

Low pressure then follows north through the region late tonight
through Sunday morning. This system will be fairly progressive,
lifting from Delmarva around midnight tonight to Long Island by
around midday Sunday. However, due to the high moisture content in
the atmosphere, there will be a 6-8 hour window during the early
morning hours on Sunday where as much as 1-2 inches of convective
rain will fall. The primary area of concern is the I-95 corridor and
surrounding urban areas and small streams where flash flooding is
more possible given any rapid runoff. It is these areas that are
under a Flood Watch for flash flooding that begins at midnight
tonight running until Noon Sunday.

Precipitation tapers off Sunday morning as low pressure departs. A
weak cold front swings through Sunday afternoon behind the low
followed by a secondary cold front Sunday night.


KEY MESSAGE 2...A cold front Thursday into Friday may bring some
showers and thunderstorms.

An upper-level trough across central into eastern Canada is forecast
to push a cold front into our area at the end of next week. While
the guidance, including ensembles, are in decent agreement showing
this trough, there are significant differences with the
amplification and therefore speed of the trough. This will have
impacts to the cold front itself. If the main energy slides far
enough north of our area, the front may tend to be slower moving.
This scenario would open the door for a greater chance for a round
of convection. A faster movement to the front would lessen the
length of convection over our area. The front may then stall to our
south into next weekend, with one or more possible waves of low
pressure tracking along it with time. A plume of deeper moisture
looks to get drawn northward ahead of this front, therefore some
heavy rain potential may exist with it and this also depends on
whether it stalls or not. Confidence remains low during this time
frame.

&&

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

Tonight...Clouds lowering and thickening with showers and some
embedded storms moving in mainly for the overnight period. MVFR
cigs beginning as early as 02-03z with IFR expected overnight.
Moderate confidence.

Sunday...Sub-VFR in SHRA in the morning, then becoming VFR by
20/21z or shortly after that as clouds scatter out. W-NW winds
generally around 5-10 knots. Moderate confidence.

Outlook...

Sunday night...Mainly VFR. A few showers possible.

Monday...VFR. North-northwest winds gusts 20-25 knots possible
during the day.

Tuesday and Wednesday...VFR.

Thursday...Mostly VFR. A few showers possible.

&&

.MARINE...
Sub-Small Craft Advisory conditions today, tonight, and Sunday.
E-SE winds 10 to 15 kt with gusts up to 20 kt today and tonight,
then W-SW winds on Sunday. Seas 2 to 4 ft.

VSBY restrictions in showers, scattered thunderstorms, and fog
late tonight through early Sunday afternoon.

Outlook...

Sunday night and Monday...A period of Small Craft Advisory wind
gusts (25 knots) are possible, mainly Monday into Monday night.

Tuesday through Thursday...The conditions are anticipated to be
below Small Craft Advisory criteria.

Rip Currents...

Sunday...Southwest winds around 10-15 mph in the morning
diminish to around 5-10 mph from the west in the afternoon.
Breaking wave heights will range between 1 to 3 feet. An
underlying 1 foot southeast swell around 8 to 10 seconds will
continue. Given these conditions, have opted to go with a
LOW risk for rip currents for all beaches.

Monday...West-northwest winds will be around 15-20 mph with seas
will remaining at 1-2 feet. The underlying 1 foot 8 to 10 second
southeasterly swell remains. Given these conditions, currently
forecasting a LOW risk for rip currents for all beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from midnight EDT tonight through Sunday morning
     for PAZ070-071-103>106.
NJ...Flood Watch from midnight EDT tonight through Sunday morning
     for NJZ008>010-012>020-026-027.
DE...Flood Watch from midnight EDT tonight through Sunday morning
     for DEZ001.
MD...None.
MARINE...None.

&&

$$

DISCUSSION...Fitzsimmons/Gorse/MPS
AVIATION...Fitzsimmons/Gorse/MPS/po
MARINE...DeSilva/Fitzsimmons/Gorse/MJL/MPS