Norristown, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

737
FXUS61 KPHI 261941
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
341 PM EDT Thu Jun 26 2025

.SYNOPSIS...
A cold front will continue to settle southward across our area
through tonight and then remain just to our south through
Friday. The front gradually lifts northward as a warm front
Saturday, followed by a weak cold front stalling nearby on
Sunday. The front then shifts northward as a warm front Monday
followed by a cold front later Tuesday. High pressure builds
closer later Wednesday into Thursday.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of early this afternoon, the back door cold front stretches
from near Allentown south to near Philly and southeast towards
Atlantic City. Locations north and east have cooled and clouded
up considerably. Further south and west, warmth and humidity
remain, and in fact it turned out the need was present to expand
the heat advisories up into Philly metro once again as heat
indices are meeting the early-season criteria once again.

Where the front has yet to reach, heat and instability have
increased, and storms are starting to develop. As these storms
start to intersect the southwestward moving front, they may
stall on the boundary, which could result in a locally heavy
rain and flood threat. HREF was most bullish across areas just
northwest and southwest of our forecast area, but enough of a
signal is present to give us confidence in posting a flood watch
for our westernmost zones in PA thru this evening. Storms may
make their way further east, with a lesser but still present
heavy rain threat, but the highest risk definitely appears to
be in the far west. There is also an increasing severe risk as
the front backs slowly south and west, with greater than
expected CAPE available, SPC has coordinated a severe
thunderstorm watch mainly for locations west and south of Philly
thru 10 PM.

Later tonight as convection winds down, the front will sweep
southwest and blanket most of the region with low clouds and a
much cooler east to northeast wind. Lows will be in the 50s
Poconos, 60s most elsewhere, but near 70 southern Delmarva
zones.

A low cloud deck will dominate Friday on the easterly flow north
of the front, which will stall just to our south. Some showers
and spotty thunderstorms may develop via disturbances passing
aloft and elevated instability, but severe and flood risk look
lower. Temperatures will struggle to reach 70 across
north/central NJ, likely failing to do so in the Poconos, but
may touch 80 across the eastern shore of MD and far southern DE.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
The much cooler conditions will ease as the onshore flow
weakens and is replaced by a southerly return flow.

An easterly flow regime is forecast to remain in place Friday
night and to start Saturday. This will then ease as surface high
pressure shifts east toward the northern Atlantic. This along
with low pressure tracking north of the Great Lakes and toward
northern Maine Saturday will result in a more return flow
setting up across our area during Saturday. This will send a
warm front northward during Saturday, bringing a much warmer and
increasingly more humid air mass back into our region for
weekend. A weak cold front then looks to settle into our area
Saturday night before stalling on Sunday.

As this occurs, some showers and thunderstorms will be possible
given the initial warm air advection and moisture advection.
This will increase the instability each day, with the
probability of precipitation the greatest Saturday afternoon
across mainly our northern and western zones. As the main system
slides by well to our north later Saturday, any severe
thunderstorm risk looks rather low. The pattern may repeat on
Sunday where some showers and thunderstorms will again be
possible, especially during the peak heating hours of the
afternoon and early evening. Temperatures are forecast to top
out at 90 degrees for some places each afternoon, especially
across the southern half of the area away from the immediate
coast. The heat indices for the majority of the area should stay
below 100 degrees each afternoon (a bit lower Sunday given some
lowering of the surface dew points).

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Summary...Potentially unsettled at times with no extreme heat
forecast.

Synoptic Overview...An upper-level trough is forecast to move
into much of the East by later Tuesday, then remain in place
through Thursday with it potentially amplifying some. At the
surface, a boundary across our area will start to lift north as
a warm front Monday, then a cold front moves through later
Tuesday. High pressure then builds closer later Wednesday into
Thursday.

For Monday and Tuesday...An upper-level trough across the
Midwest and adjacent Canada Monday is forecast to shift eastward
and amplify some. This overspreads the Northeast with it
possibly amplifying a bit more as stronger shortwave energy
rounds the base of the trough. This will drive a cold front
toward our area later Monday, then cross our region by later
Tuesday. Increasing mid level flow will result in an uptick in
shear and instability should be sufficient enough for some
thunderstorm development. There could be some severe
thunderstorm risk Tuesday afternoon as the cold front arrives in
tandem with the incoming upper-level trough. Some showers or
thunderstorms cannot be ruled out on Monday especially in the
afternoon and evening, primarily tied to a surface trough.
Temperatures will make a run at 90 degrees for many areas with
Tuesday potentially the hotter day as dew points surge ahead of
the cold front. While it will be rather warm and humid, extreme
heat is currently not forecast.

For Wednesday and Thursday...The upper-level trough across the
Northeast and Mid-Atlantic may tend to sharpen again as
additional energy rounds its base. The cold front should be
south and east of our area to start Wednesday, and while
temperatures do not look to drop much, the dew points are
forecast to lower some in the wake of the cold front. Despite
the presence of the upper-level trough, less in the way of
deeper moisture should keep the instability lower as well. Given
surface high pressure building closer to our area later
Wednesday and especially Thursday, the chance for any showers
and thunderstorms at this time looks to be rather low.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
Rest of today...Mainly VFR, but sub-VFR possible mainly from
PHL north and east as backdoor front brings stratus deck. Spotty
showers/t-storms possible during the afternoon especially
western terminals. Winds turning northeasterly 5-10 kts. Low
confidence.

Tonight...Sub-VFR conditions likely with IFR possible. Scattered
storms this evening give way to widespread low stratus later at
night. Winds northeast to east 5-10 kts. Low confidence.

Friday...Sub-VFR conditions likely with IFR possible. Scattered
showers possible, but main concern will be continued low stratus
deck which likely lingers most if not all day. Winds still east
to northeast 5-10 kts. Low confidence.

Outlook...

Friday night...MVFR/IFR ceilings due to low clouds. Some
showers are possible which could result in visibility
restrictions at times.

Saturday...IFR or MVFR ceilings improve to VFR. Some showers or
thunderstorms possible.

Sunday and Monday...A few showers and thunderstorms, resulting
in lower ceilings/visibilities at times, are possible.

Tuesday...Some showers and thunderstorms probable with local
restrictions.

&&

.MARINE...
Small Craft Advisory thru Friday afternoon for northern two NJ
marine zone given northeast flow gusting 25-30 kts which likely
continues into Friday, with seas building to 3-5 feet. Rest of
zones should see NE winds 10-15 kts with some gusts up to 20
kts thru Friday and seas of 2-4 feet. A spotty gusty
thunderstorm possible this afternoon/evening.

Outlook...

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

Rip Currents...

For Friday, onshore flow with east winds around 15 to 20 mph will
continue with seas off the coast building to around 3 to 4 feet. For
this reason, there is a MODERATE risk for the development of
dangerous rip currents for both the Jersey Shore and the Delaware
Beaches.

For Saturday, the flow turns southerly so there will be less of an
onshore component however the seas will continue to be around 3 to 4
feet. For this reason we`ll continue with a MODERATE risk for the
development of dangerous rip currents for the NJ Shore with a LOW
risk for the Delaware Beaches.

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

&&

.TIDES/COASTAL FLOODING...
The recent New Moon and increasing onshore flow will lead to higher
confidence in advisory level tidal flooding occurring this evening.
While we are getting away from the New Moon, onshore flow will
result in water piling up and more widespread minor tidal flooding
for the coastal and Delaware Bay communities. The Coastal Flood
Advisory was expanded this afternoon to include all counties along
the Delaware Bay. It appears that the higher water at advisory
levels will only be for one tide cycle, but we`ll monitor later
today to assure that this trend continues.

No tidal flooding is expected within the tidal Delaware River or
Chesapeake Bay.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 8 PM EDT this evening for PAZ070-071-102-
     104.
     Flood Watch until midnight EDT tonight for PAZ054-060-061-101-
     102.
NJ...Heat Advisory until 8 PM EDT this evening for NJZ017-018.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Friday for NJZ016.
     Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
     Friday for NJZ012>014-020>027.
DE...Heat Advisory until 8 PM EDT this evening for DEZ001>003.
     Coastal Flood Advisory from 10 PM this evening to 2 AM EDT
     Friday for DEZ001.
     Coastal Flood Advisory from 7 PM this evening to 1 AM EDT
     Friday for DEZ002>004.
MD...Heat Advisory until 8 PM EDT this evening for MDZ012-015-019-
     020.
MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ450-451.

&&

$$

SYNOPSIS...Gorse/RCM
NEAR TERM...RCM
SHORT TERM...Gorse
LONG TERM...Gorse
AVIATION...Gorse/RCM
MARINE...Fitzsimmons/Gorse/RCM
TIDES/COASTAL FLOODING...