414
FXUS61 KPHI 210118
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
918 PM EDT Thu Aug 20 2026

.WHAT HAS CHANGED...
Severe thunderstorm and tornado watches have been cancelled.

Flood watch has been cancelled.

Small craft advisory is issued for this evening and overnight.

Made adjustments to the wind forecast for the evening and
overnight hours, along with updates to aviation and marine
forecasts.

&&

.KEY MESSAGES...
1. A cold front will cross the region this evening, resulting
in widespread showers and thunderstorms. Flash flooding,
damaging wind gusts and tornadoes are possible later today.

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...
Strong winds behind the convective activity appear to be in the
wake of the two surface waves moving along the front have keep
winds up out of the north and northeast. Have adjusted the
forecast for the gusts. Heavy precipitation materialized earlier
today with some impressive rainfall totals especially across
southern NJ. With the risk of additional flooding low, the flood
watch is cancelled. Remainder below is unchanged.


Broad troughing will be the main driving force in the sensible
weather into the early to middle part of next week across much
of the Eastern Seaboard. A shortwave will round the base of the
trough today into this evening providing some mid level synoptic
forcing. At the surface a warm front has lifted north into the
Philadelphia metro area with a cold front approaching from the
west.

The trend for increasing QPF and increasing severe weather
potential is being realized this afternoon. Severe thunderstorm,
tornado, and flood watches are in effect for most of the
forecast area.

Mesoanalysis fields this afternoon show moderate to strong
instability centered roughly around the Delmarva peninsula, but
extending north into southern NJ and southeast PA. Deep layer
shear of 40-60kt along with backed low level flow and strongly
curved hodographs will support a tornado risk, most notably from
the Philadelphia metro area and points south. Primary mode at
the moment is supercellular with all attendant risks, but more
multicell clusters may become the primary mode along the cold
front.

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.
The cold front crossing the area tonight will stall in the
offshore waters. waves of low pressure will ride along the
stalled front resulting in unsettled weather through the
weekend. The main periods to watch are early Saturday through
Saturday evening, with periods of rain increasingly likely, and
again on Sunday. The severe threat appears low at this time but
there could be additional flooding concerns, although no day
has more than a Marginal (1/5) Risk for excessive rainfall.

Temperatures will be seasonable, but humidity will be
uncomfortable.


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

Weak high pressure looks to bring quieter and drier weather in
the early part of the week, with more unsettled conditions
expected later in the week with seasonable temperatures.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Quick update to make wind adjustments in the wake of the front,
mostly VFR behind the precipitation but still some risk of MVFR
conditions for a few hours this evening. Remainder unchanged
below.

Tonight...Sub-VFR conditions probable at times with showers and
thunderstorms continuing into the evening hours. Fog and/or low
stratus possible at night after the precipitation moves out.
Conditions should lift back to VFR near or not long after
daybreak. North/northeast winds around 5 to 10 kt. Moderate
confidence.

Outlook...

Friday through Friday night...Primarily VFR.

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...
Have increased gusts in the Delaware Bay and Atlantic coastal
waters this evening to account for the strong winds around the
surface low moving along the front. The winds should diminish
toward morning. Have issued a small craft advisory for all of the
waters through daybreak. Remainder below unchanged.

A cold front will move through tonight, with winds becoming
more north/northeasterly around 10-15 kt. Seas of 2 to 3 feet.
Showers and thunderstorms expected on the waters this evening
into tonight.

Outlook...

Friday through Monday...No marine headlines expected. Showers
and thunderstorms possible during the day Friday through
Sunday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ430-431-
     450>455.

&&

$$

DISCUSSION...Manning
AVIATION...Manning/PW
MARINE...Manning