Norristown, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

303
FXUS61 KPHI 282103
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
503 PM EDT Sun Jun 28 2026

.WHAT HAS CHANGED...
No significant changes from previous discussion.

&&

.KEY MESSAGES...
1. A few showers or maybe a thunderstorm are possible into the
early evening.

2. A large area of high pressure will set up over the Midwest,
resulting in high heat and humidity over the Northeast and Mid-
Atlantic. High temperatures will be well in the upper 90s to as
high as 105 degrees with maximum heat index values between 100
and 110 degrees from Wednesday through Saturday.

3. There is the potential for afternoon and evening
thunderstorms starting on Friday and lasting into the holiday
weekend.

&&

.DISCUSSION...
KEY MESSAGE 1... A few showers or maybe a thunderstorm are
possible into the early evening.

A stalled front well to the south and weak high pressure
building in across NY/NE will keep a light onshore flow across
the area tonight and Monday. This humid airmass may yield a few
showers this evening and perhaps a isolated one on Monday as
some upper shortwave energy moves across PA/NJ. The chances will
remain low (around 20% this evening and 10% for Monday). A tstm
is possible but we`ll only keep a slight chance for that attm.
Any tstm is capable of producing decent downpours however with
the high PWAT airmass in place.


KEY MESSAGE 2...A large area of high pressure will set up over
the Midwest, resulting in high heat and humidity over the
Northeast and Mid-Atlantic. High temperatures will be well in
the upper 90s to as high as 105 degrees with maximum heat index
values between 100 and 110 degrees from Wednesday through
Saturday.

Strong mid-level ridging develops over the Great Lakes and Ohio
Valley early this week. The high then builds into the Northeast
and Mid-Atlantic by Wednesday and continues through into the
holiday weekend. In general, a west to southwest flow develops
on Wednesday, then becomes more west to northwest by Friday.
High temperatures will climb into the mid and upper 90s on
Wednesday, and then from 100 to 105 on Thursday and Friday.
Temperatures will abate somewhat on Saturday, returning to the
mid and upper 90s. However, with dew points in the 60s and 70s,
this will yield max heat index values from 105 to 110 during the
two hottest days, which will be Thursday and Friday. Still, max
heat index values will be 100 to 105 on Wednesday and Saturday.

The Extreme Heat Watch remains in effect for New Jersey,
southeast Pennsylvania, the Delaware Valley including
Philadelphia and northern Delaware, and the southern Poconos.
Future shifts will likely expand the Watch to include the rest
of Delmarva.

The mid-level ridge will break and retrograde back towards the
south and west on Saturday, and a mid-level trough will try to
slide down into the Northeast. This pattern change will begin to
favor slightly cooler temperatures and a break in the extreme
heat by Sunday or Monday, as well as the potential for showers
and thunderstorms next weekend (see Key Message 3 below).


KEY MESSAGE 3...There is the potential for afternoon and
evening thunderstorms starting on Friday and lasting into the
holiday weekend.

The mid-level ridge looks to break down and retrograde back to
the south and west starting on Friday, and this will allow mid-
level troughiness to develop over the Northeast. With several
shortwaves riding over the top of the ridge and into the local
area, this may touch off afternoon and evening showers and
thunderstorms starting on Friday, but the better chances for
convection arrive on Saturday and Sunday. Currently, PoPs are
around 20 percent (slight chance) on Friday and 30 to 50 percent
(chance) on Saturday and Sunday. Given the high heat and
humidity, cannot rule out at least a few stronger thunderstorms.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

thru sunset... Scattered showers perhaps an isolated tstm
possible for many sites with VCSH inserted in the latest TAFs.
CIGS will mostly remain high-end MVFR or low-end VFR with some
improvement possible thru early tonight. Light E/SE winds.
Low/medium confid.

Tonight... Gradually diminishing conditions after sunset as low
level moisture arrives as ST clouds slowly advect from the
South/East. Fog will develop across the northern/western
terminals where some cooling occurs early. Overall. most sites
heading for low MVFR or high IFR conditions many areas between
03Z/07Z. Light E/SE winds. Low confid.

Monday... Slow improvement back to VFR (11Z-14Z) then probably
VFR afterwards. Couple afternoon showers possible N/W.
Low/medium confid.

Outlook...

Monday night...Potential for VSBY restrictions in BR.

Tuesday through Friday...VFR. NSW.

&&

.MARINE...
Good conditions across the waters with sub-SCA continuing into
the overnight. A couple scattered showers are possible across
Delaware Bay or the southern NJ and Delaware waters, but the
chances are rather low. Winds will remain light 5 to 10 knots
from the E or SE. Similar conditions for Monday. Aside from the
showers a little fog is possible overnight and into early
Monday.

Outlook...

Monday night through Friday...Overall, sub-SCA conditions
expected. Cannot rule out a brief period of southerly 25+ kt
gusts or seas approaching 5 feet late Tuesday and/or Wednesday
afternoon, mainly north of Barnegat Light.

Rip Currents...

For Monday, breaking waves in the surf zone will be around 2
feet or less with east to northeast winds around 10 mph and a
southeast swell. As a result, there is a LOW risk of dangerous
rip currents for both the Jersey Shore and Delaware Beaches.

For Tuesday, conditions remain similar, with east to southeast
winds around 10-15 mph and a southeast swell. Breaking waves in
the surf zone will be around 1-2 feet as a result, and
therefore, the LOW risk of dangerous rip currents for both the
Jersey Shore and Delaware Beaches looks to continue.

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

&&

.CLIMATE...
Here is a list of the high temperature records for July 2
(Thursday) and July 3 (Friday):

Thursday July 2
Allentown...102/1968
Atlantic City Airport...100/1966
Atlantic City Marina...97/1968
Georgetown...99/1953
Mount Pocono...93/1911
Philadelphia...103/1901
Reading...102/1966
Trenton...100/1901
Wilmington...98/1966

Friday July 3
Allentown...105/1966
Atlantic City Airport...104/1966
Atlantic City Marina...99/1919
Georgetown...101/1954
Mount Pocono...103/1911
Philadelphia...104/1966
Reading...103/1966
Trenton...102/1966
Wilmington...102/1966

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Extreme Heat Watch from Wednesday afternoon through Saturday
     evening for PAZ054-055-060>062-070-071-101>106.
NJ...Extreme Heat Watch from Wednesday afternoon through Saturday
     evening for NJZ001-007>010-012>027.
DE...Extreme Heat Watch from Wednesday afternoon through Saturday
     evening for DEZ001.
MD...None.
MARINE...None.

&&

$$

DISCUSSION...MPS/OHara
AVIATION...MPS/OHara
MARINE...AKL/MPS/OHara