145
FXUS61 KPHI 192345
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
Issued by National Weather Service New York NY
745 PM EDT Wed Aug 19 2026

.WHAT HAS CHANGED...
A Flash Flood Watch has been issued for portions of southeast
PA, northern DE and New Jersey from 12 PM Thursday through 2 AM
Friday.

The Slight Risk (2/4) for Excessive Rainfall has been expanded
further north into portions of northern NJ.

A Slight Risk (2/5) for Severe Weather has been introduced
across portions of southeast PA, southern NJ, and the Delmarva.

Aviation section updated for 00Z TAFs.

&&

.KEY MESSAGES...
1. A strong cold front is expected to cross through the region
on Thursday, resulting in widespread showers and thunderstorms.
Flash flooding and severe weather, including all hazards are
possible.

2. Conditions look to remain unsettled through the weekend,
with daily chances of showers and storms each day.

3. Fair weather is expected to return for early next week.

&&

.DISCUSSION...
KEY MESSAGE 1...A strong cold front is expected to cross
through the region on Thursday, resulting in widespread showers
and thunderstorms. Flash flooding and severe weather, including
all hazards are possible.

To the south of a closed upper low over eastern Canada, broad
troughing will be in place across much of the Northeast and Mid-
Atlantic. An embedded mid-level shortwave will pass through the
base of the trough on Thursday. At the surface, a warm front
will move into portions of the area tonight as a cold front will
begin to approach the area on Thursday.

With guidance coming into better agreement with the timing and
placement of frontal boundaries in our area, there has been an
uptick in confidence in what the evolution could be on Thursday.
For now, multiple rounds of widespread showers and storms are
expected. With the cold front approaching from the west, and a
warm front expected to set-up across the southern half of the
area across the Delmarva and into southern New Jersey, we will
have to watch these areas for severe weather Thursday afternoon
and evening. In fact, SPC has upgraded portions of the area to a
SLIGHT risk for severe weather (Level 2/5) with a MARGINAL risk
elsewhere. Bulk shear values up to 30-40 kt support organized
clusters where locally damaging wind gusts are possible. With
the warm front draped over portions of the area, there will be a
localized corridor of a tornado threat, especially where any
storm is able to latch onto the boundary. The best guess of
where this may occur is somewhere in the Delmarva to southern
New Jersey corridor where SPC has introduced a 2% tornado risk
with locally backed flow at the surface. Cannot rule out
isolated large hail as well as temperatures aloft are rather
cool for this time of year. There should be an abundance of
clouds in place on Thursday, so this could hinder the magnitude
of the severe threat to some degree.

The other, and possibly more concerning threat may be the risk
and potential for flash flooding across portions of the area.
Most guidance continues to depict a very moisture rich airmass
surging northward on Thursday where PWAT values are expected to
top out around 2.2-2.6 inches. Model forecast soundings also
show tall, skinny CAPE profiles and a relatively deep warm cloud
layer. The one saving grace is that the overall shear vectors
indicate that storms should be `relatively` quick moving.
However, any given storm will be capable of producing highly
efficient rain rates, at times around 2 to 3+ inches per hour.
With this being said, WPC has maintained a SLIGHT risk (Level
2/4) for excessive rainfall on Thursday, but has expanded the
risk further north to incorporate northern New Jersey. In
general, expecting anywhere between 1 to 2 inches of rain to
fall, with localized higher amounts up to 3 to 5 inches. This is
supported by most of the 12Z guidance suite today, especially
where the HREF LPMM show localized bullseyes of higher rainfall.
Given the increased confidence in flooding potential, have
opted to issue a Flash Flood Watch for portions of southeast PA,
northern Delaware, and New Jersey from 12 PM Thursday through 2
AM Friday.

The severe and flooding rain threat should diminish overnight
into Friday morning.


KEY MESSAGE 2...Conditions look to remain unsettled through the
weekend, with daily chances of showers and storms each day.

Mid to long range NWP and AI guidance suggests that the pattern
could become unsettled Friday night and into the weekend.
Depending on how the frontal boundary evolution pans out on
Thursday, will impact the weather over the weekend. Most
guidance does suggest that the frontal boundary will stall over
or in close proximity of the area where several areas of low
pressure may ride along the stalled boundary through the
weekend. PoPs are currently in the 40-80% range on Saturday and
30-60% range on Sunday. Given the present uncertainties in
timing and placement of the frontal features and progression in
the long wave pattern, have opted to keep very close to the NBM.

In terms of temps, highs and lows will both be quite seasonable
for late August, but humidity levels may be uncomfortable at
times.


KEY MESSAGE 3...Fair weather is expected to return for early
next week.

High pressure looks to bring fair and tranquil weather to start
next week. The pattern potentially becomes more active again
towards the middle to end of next week.

&&

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

Tonight...VFR with increasing high clouds. West-southwest winds
around 5 kt or less early, becoming light and variable
overnight. Moderate-high confidence.

Thursday...VFR in the morning with restrictions likely
developing in the afternoon (primarily after 16Z), as
widespread showers and thunderstorms are likely at all
terminals. Any storms will be capable of producing very heavy
rainfall and LIFR conditions. Winds will vary depending on
location, with northern terminals experiencing east- northeast
winds around 5 kt where southern terminals will encounter
southeasterly winds around 5-10 kt. Winds may locally become
gusty and erratic near any storm. Showers and storms ending by
00Z. Moderate confidence overall, but low confidence on exact
timing details.

Outlook...

Thursday night...Sub-VFR conditions probable at times with
showers and thunderstorms continuing into the evening hours,
before diminishing overnight. Fog and/or low stratus possible
at night.

Friday through Friday night...Primarily VFR, though cannot rule
out isolated showers/thunderstorms for southern terminals which
could result in some restrictions.

Saturday through Sunday...Periods of VFR and sub-VFR at times.
Restrictions expected with daily chances for showers and
thunderstorms.

Monday...VFR. No significant weather expected.

&&

.MARINE...
No marine headlines expected through Thursday. South-southwest
winds around 10-15 kt with seas around 1 to 2 feet.

Fair weather expected through Thursday morning, before
widespread showers and thunderstorms develop in the afternoon
and evening hours. Locally gusty and erratic winds will be
possible near/in any thunderstorm. Waterspouts are also
possible.

Outlook...

Friday through Monday...No marine headlines anticipated. Daily
showers and storms possible on all waters Friday through Sunday.
Fair weather returns on Monday.

Rip Currents...

For Thursday, south to southeast winds increasing to near 10 mph.
Breaking waves will average around 1 to 2 feet. There will
continue to be a southeasterly swell with a 6 to 8 second
period. The result of these conditions is a LOW risk for the
development of dangerous and life threatening rip currents for
the Jersey Shore and Delaware Beaches.

For Friday, north to northeast winds will be near 10 to 15 mph.
Breaking waves will average around 1 to 2 feet. There will
continue to be a southeasterly swell with a 6 to 9 second
period. The result of these conditions is a LOW risk for the
development of dangerous and life threatening rip currents for
the Jersey Shore and Delaware Beaches.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch from Thursday afternoon through late Thursday
     night for PAZ070-071-101>106.
NJ...Flood Watch from Thursday afternoon through late Thursday
     night for NJZ009-010-012>022-025>027.
DE...Flood Watch from Thursday afternoon through late Thursday
     night for DEZ001.
MD...None.
MARINE...None.

&&

$$

DISCUSSION...DeSilva/Fitzsimmons/Staarmann
AVIATION...DeSilva/Staarmann
MARINE...DeSilva/Staarmann