Tredyffrin, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

804
FXUS61 KPHI 201428
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1028 AM EDT Sun Jul 20 2025

.SYNOPSIS...
A cold front approaches later today and passes through the
region tonight. Canadian high pressure builds in from the north
and west for the start of the new work week, eventually moving
offshore by Thursday. A cold front approaches late this week and
next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Leftover low clouds will dissipate by 16Z. Increasing southwest
flow will usher a warmer and more humid airmass into the
region. Highs today will top off in the upper 80s to around 90.
Surface dew points will generally be in the low to mid 70s, but
afternoon mixing should keep dew points from getting into the
upper 70s. Max heat index values will be in the mid to upper
90s, and near 100 in Delmarva.

The cold front approaches this afternoon. Surface-based CAPE
values will be up around 2000 J/kg, and 0-6 km Bulk Shear will
be around 35 kt. Thunderstorms that develop may contain strong
to damaging wind gusts, some hail, and torrential downpours.
Storm coverage will not be widespread, but the main focus will
be on northern New Jersey, as well as portions of the Lehigh
Valley and Poconos, as these areas will be closer to the base of
an upper level trough. In these areas there is a Slight Risk (2
out of 5) for severe weather. A Marginal Risk (1 out of 5) for
severe weather lies mainly north of a Wilmington, DE to Atlantic
City, NJ line.

The cold front moves through tonight, and cooler and much drier
air builds into the region. Surface dew points will drop from
the low to mid 70s into the mid and upper 60s. Lows tonight will
be in the 60s to low 70s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Behind the cold front, a much more pleasant airmass builds into
the region as Canadian high pressure builds into the Great
Lakes, and cold air advection will be underway due to northerly
winds ahead of the high. Surface dew points will drop into the
50s and low 60s on Monday, and then into the mid and upper 50s
for most of the area, and into the low 60s in Delmarva and
extreme southern New Jersey on Tuesday. Highs on Monday will be
low to mid 80s on Monday, and then a few degrees cooler on
Tuesday. Comfortable nights on tap with lows in the 50s to low
60s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
High pressure will be in control for most of the week. The
center of the high will be over New England Wednesday, and then
offshore by Thursday. Conditions will be dry and mild, though
return flow setting up behind the high will result in increasing
humidity and temperatures. Highs will be back up in the upper
80s to near 90 on Thursday.

A cold front approaches Friday and does not look to cross the
area until Friday night. Another front approaches on Saturday.
This will bring the next chances for showers and thunderstorms
to the area.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Low clouds should continue to dissipate, and VFR
conditions return by 15Z the latest. Widely scattered afternoon
SHRA/TSRA that could result in brief sub-VFR conditions. SW
winds 5 to 10 kt this morning, then 10 to 15 kt with gusts up to
20 kt this afternoon. Moderate confidence.

Tonight...Lingering SHRA/TSRA will taper off in the evening.
VFR otherwise. W winds 5 to 10 kt become NW. High confidence.

Outlook...

Monday through Thursday...VFR. NSW.

&&

.MARINE...
Sub-Small Craft Advisory conditions today and tonight. SW winds
will be 10 to 15 kt with gusts up to 20 kt, and then winds turn
NW tonight behind a cold front.

Scattered showers and thunderstorms this afternoon and evening
may result in VSBY restrictions in heavy rain, as well as
potentially damaging wind gusts.

Outlook...

Monday through Thursday...A prolonged period of sub-SCA
conditions. There is the potential for 25 kt wind gusts on the
New Jersey Atlantic waters Thursday.

Rip Currents...

Today, southwest winds will be around 10 mph along with
breaking waves of 1 to 2 feet and a period of 7 to 8 seconds. As
a result, there is a LOW risk for the development of dangerous
and life threatening rip currents at the Jersey Shore and
Delaware Beaches.

On Monday, winds will be out of the north and gradually become
more easterly to even southeast by the evening at 5 to 10 mph.
Breaking waves of 1 to 2 feet and a period of 8 to 9 seconds. As
a result, there is a LOW risk for the development of dangerous
and life threatening rip currents at the Jersey Shore and
Delaware Beaches.

Rip currents occur often in the vicinities of jetties and piers
and the speed of the currents are generally maximized at low
tides.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...MPS
NEAR TERM...Franklin/MPS
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...Johnson/MPS
MARINE...MPS