969
FXUS61 KPHI 280653
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
253 AM EDT Tue Jul 28 2026

.WHAT HAS CHANGED...
The Flood Watch from I-78 on north was extended to now go
through Wednesday Evening.

Moderate Risk for Excessive Rainfall (Level 3 of 4) was expanded
to now include the Philadelphia metro area and I-95 corridor.

&&

.KEY MESSAGES...
1. A significant system begins to impact the region today with
flash flooding and severe weather all on the table. The
flooding threat will continue into Wednesday. A Flood Watch is
in place for most of New Jersey, all of eastern Pennsylvania,
and northern Delaware.

&&

.DISCUSSION...
KEY MESSAGE 1...A significant system begins to impact the
region today with flash flooding and severe weather all on the
table. The flooding threat will continue into Wednesday. A
Flood Watch is in place for most of New Jersey, all of eastern
Pennsylvania, and northern Delaware.

Only one key message in the discussion this morning but impacts
are expected to be felt region-wide and over multiple days. The
most significant and impactful day will be today though as a
deepening area of low pressure moves toward New York, with a
warm front lifting through today and a strong cold front coming
in tonight. The front, aided by strong jet dynamics, will
provide ample lift for widespread showers and thunderstorms and
perhaps multiple rounds today and into tonight.

We will break out the hazards and threats by starting with the
flash flooding threat over the next two days. A lifting warm
front will only strengthen southerly flow through today,
ushering in a very moist airmass. PWATs will approach two
inches which is over the 90th percentile even for late July. A
warm cloud layer over 10k feet will also aid in producing very
efficient rainfall rates. Rates of 1-3" per hour are expected
later this afternoon and evening. This, combined with the
potential for multiple rounds of precipitation will result in a
pretty significant flash flood threat. And the new WPC Excessive
Rainfall Outlook reflects that, expanding the MODERATE (3/4)
Risk for Excessive Rainfall into the Philly area and extending
along the I-95 corridor down into northern Delaware. These more
urban areas begin to see flash flooding generally around 1" per
hour and that seems very likely considering today`s setup
especially in the afternoon and evening. Some areas may also be
more flood prone, given yesterday`s rainfall where there were
some flooding reports.

No significant changes in the Flood Watch, which remains in
place for most of New Jersey, all of eastern Pennsylvania, and
northern Delaware. Lower rainfall amounts and areas more in need
of rainfall over far South Jersey and most of Delmarva will
result in a lesser flood threat and those areas staying outside
of the watch. Cannot rule out flash flooding entirely though in
these areas (as we saw yesterday in localized spots) and most of
South Jersy and Delmarva remains in either a Marginal (1/4) or
Slight (2/4) Risk for Excessive Rainfall.

The one minor change was extending the Flood Watch north of I-78
through Wednesday. As low pressure meanders, another front will
come through on Wednesday, capable of producing some heavy
downpours yet again for the northern third of the region. This
will move over some more urbanized areas in North Jersey that
should get a decent amount of rainfall today, potentially
causing more problems. While mainstem river flooding is not
currently forecast, some smaller creeks and streams within the
Passaic and Raritan basins could see some rises that result in
flooding.

When all is said and done, the current QPF forecast through
Wednesday has around 2 to 5 inches of rain north of I-78, with 1
to 3 inches elsewhere. As is usual in summer convective setups,
locally higher amounts are possible. HREF Max in northern New
Jersey has highly localized amounts up to 8" through Wednesday.
Have multiple ways to receive any flood alerts.

In terms of the severe threat, no significant changes were made
to the forecast. Unlike the hydro threat, the severe threat will
be more focused on the southern half of the area. SPC did nudge
the Slight Risk (2/5) a touch south, having far southeast PA,
South Jersey, and all of Delmarva in. The Marginal Risk (1/5) is
in place from Philadelphia on north. Instability will increase
quickly once the warm front passes. Delmarva and South Jersey
will have more time in the warm sector and have higher amounts
of shear to work with. The limiting factor further north towards
Philly and points north will be the amount of cloud cover. Main
timing window is from 2 PM through about 11 PM and damaging
wind gusts the primary threat. Cannot rule out a tornado, though
the tornado threat will be more focused over Delmarva. No area
is currently in any severe outlook category for Wednesday.

Guidance continues to have the surface low to the north
potentially lingering through Thursday, though impacts should
mainly be confined through tomorrow. High pressure nudges in
towards the end of the week and for the weekend, giving us a
break from the active pattern.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Tonight...VFR for the next few hours before some
MVFR/IFR stratus develops and moves over the region around
09z-10z. Cannot rule out some patchy fog either, mainly at KRDG
and KMIV. Winds generally out of the south around 5 kt or less.
Low confidence.

Today...Tricky forecast ahead as an active and unsettled day is
expected. MVFR/IFR stratus should be in place but could lift to
VFR as the morning goes on. Showers and thunderstorms develop
off to the west by the late morning, and should impact all
terminals, mainly in the afternoon and evening. Have added TEMPO
TSRA groups at all terminals, generally in the 18z-22z window
give or take an hour or two depending on the site. Gusty and
erratic winds are also possible within any convection. Periods
of rain and thunderstorms could continue beyond 00z, especially
from the I-95 corridor on east, but kept all thunder mention
prior to 00z. Confidence is very low in how things evolve. Winds
will generally be out of the south around 5-10 kt, with stronger
winds of 10-15 kt and gusts near 20 kt at KMIV/KACY. Low
confidence.

Tuesday Night...MVFR/IFR conditions expected for at least the
first half of the night with rain and thunderstorms moving out,
though some guidance has conditions improving for the second
half of the night. Low confidence.

Outlook...

Wednesday through Thursday...Primarily VFR though an unsettled
pattern will result in some restrictions with showers, low
clouds, and isolated thunderstorms, especially from KPHL on
north.

Thursday Night through Saturday...VFR. No significant weather.

&&

.MARINE...
Sub-SCA conditions expected through the morning with southerly
winds around 10-20 kt and seas 2 to 4 feet.

The Small Craft Advisory remains, beginning at noon for all
marine zones as southerly wind gusts around 25 kt are expected
with seas around 5 feet. The SCA expires at 8 PM for Delaware
Bay but continues through tonight for all ocean zones as 5 foot
seas linger. Showers and thunderstorms expected on the waters
this afternoon through tonight.

Outlook...

Wednesday through Saturday...No marine headlines anticipated.

Rip Currents...

For Tuesday, southerly flow will increase as the day progresses
causing winds to increase from around 10 to 15 mph to around 15
to 25 mph in the afternoon with gusts up to 30 mph possible.
Multiple swell groups generally around 2 to 4 feet are expected.
With only 1 day prior to the full moon phase and average swell
periods around 5-7 seconds, opted to continue with a MODERATE
risk for dangerous rip currents for both the Jersey Shore and
Delaware Beaches.

For Wednesday, winds will vary depending on the beaches where
the southern Jersey Shore and Delaware Beaches will generally
have west winds around 10 to 15 mph where northern Jersey Shore
beaches will have south winds around 10 to 20 mph. Breaking wave
heights will average between 1 to 3 feet. With the Full Moon
Phase occuring on Wednesday, have opted to go with a MODERATE
risk for dangerous rip currents at all beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from 8 AM EDT this morning through Wednesday
     afternoon for PAZ060-070-071-101>106.
     Flood Watch from 8 AM EDT this morning through Wednesday
     evening for PAZ054-055-061-062.
NJ...Flood Watch from 8 AM EDT this morning through Wednesday
     afternoon for NJZ013>020-026-027.
     Flood Watch from 8 AM EDT this morning through Wednesday
     evening for NJZ001-007>010-012.
DE...Flood Watch from 8 AM EDT this morning through Wednesday
     afternoon for DEZ001.
MD...None.
MARINE...Small Craft Advisory from noon today to 8 PM EDT this evening
     for ANZ430-431.
     Small Craft Advisory from noon today to 6 AM EDT Wednesday for
     ANZ450>455.

&&

$$

DISCUSSION...Hoeflich
AVIATION...Hoeflich
MARINE...Hoeflich