Upper Merion, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

913
FXUS61 KPHI 260139
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
939 PM EDT Fri Apr 25 2025

.SYNOPSIS...
A warm front will lift north across the Mid Atlantic this evening
followed by a cold front on Saturday. High pressure will build in
behind the low pressure system for Sunday and persist through
Tuesday. A cold front is expected on Wednesday. More high pressure is
expected Thursday and Friday.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 940 PM, a few minor adjustments were made along the
coastal strip to account for slightly later arrival of low
clouds and patchy fog. No changes otherwise.

A round of showers with embedded thunder is expected tonight
into early Saturday associated with a shortwave trough. A second
round of scattered showers and storms is expected Saturday
afternoon into the early evening hours associated with a cold
front passage.

Convective showers over the Ohio Valley and Mid-Atlantic will
lift northeast this evening and continue through the overnight
hours (the bulk of activity will be after midnight). Other than
some brief heavy downpours and some rumbles of thunder around,
the activity tonight does not look like it will amount to all
that much. Greatest potential for showers/storms is north and
west of the I-95 corridor, but some of the latest hi-res
guidance indicates more of a signal to having some convective
showers all the way down to the coast. Lows tonight will be very
mild with lows in the mid 50s to low 60s. Patchy to localized
dense fog will be possible along the coastal strip as well.

The morning precipitation is expected to exit the area by day break
for the majority of the area except for portions of the Poconos and
northern New Jersey where shower activity may continue into the late
morning hours. All in all, there should be a lull in shower activity
during the morning hours in between departing shortwave and
approaching cold front. Despite the lull in activity, pesky cloud
cover looks to remain in place for much of the day, so skies should
primarily be mostly cloudy with occasional breaks of sun in the
afternoon. The second round of showers and thunderstorms are then
expected to develop by the early afternoon hours. Latest 12Z/HREF
probabilities have increased the amount of surface based instability
just a bit, with ~1000 J/kg of SBCAPE and ~25 kt of bulk shear
available during the afternoon. This of course depends on how much
sunshine is able to occur during the day to set the stage on how
much the area may destabilize. Considering the above parameters and
latest guidance trends by the HRRR/ARW/RRFS, scattered showers and
storms may organize into broken clusters as they progress eastward
through the afternoon hours ahead of the cold front. Although none
of the area is currently outlooked by SPC, do believe there may be a
couple strong to severe storms around Saturday afternoon. Primary
threat would be damaging wind gusts if any organized clusters are to
develop. Convective activity will cease from northwest to southeast
during the afternoon as the front progresses through the area.

Aside from the afternoon convection, high temperatures on
Saturday are expected to top out in the upper 60s to upper 70s.
Winds will also be gusty at times out of the southwest, with a
few gusts 20-30 mph possible.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
The period begins with mid-level low pressure to our north. At the
surface, a cold front will be just to our east. This cold front will
continue to track offshore with a tightening gradient behind it.

Showers will be coming to an end on Saturday night. A good amount of
sunshine will be in place on Sunday, especially across the southern
half of the forecast area. Definitely more clouds to the north.

The mid-level low will push off to our northeast Sunday night. At
the surface, high pressure will begin to build in. While the mid-
level NW flow will persist on Monday, the surface high will pass
overhead and center itself just off the coast late on Monday.

After a breezy day on Sunday, winds will relax Sunday night and be
on the lighter side on Monday.

Saturday and Sunday night lows will will be similar with the upper
30s in the Southern Poconos and in the 40s everywhere else.

Sunday will be the cooler day of the weekend in the post-frontal
environment. Highs will be in the 50s across the north and 60s
south. Expect 60s and 70s on Monday.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Surface high pressure will remain in place Monday night, but begin
to unravel on Tuesday. This will allow a cold front to move through
the region on Wednesday. Weak surface high pressure will build once
again Thursday. A warm front will first approach the region on
Friday followed by a cold front. In short, expect a couple shots of
precipitation the second half of the week.

Overnight lows Monday night will be around normal. Temperatures will
move into the above normal category on Tuesday and stay there
through much of the week. While the guidance has come down from its
earlier peak in the mid to upper 80`s on Tuesday and/or Wednesday,
lower 80s still look reasonable. Thursday`s temperatures look
normal. Friday could move above normal.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR ceilings will lower to MVFR by 02-04Z and to IFR
by 05-07Z. Scattered rain showers with embedded thunder will be
possible beginning as early as 03Z and continuing through the
night. Confidence in some thunder occurring is now high enough
to include for the I-95 terminals after 07Z. South wind around
10 kt. LLWS possible for all terminals developing after 06Z
excluding KRDG/KABE. Patchy fog is also possible for KACY/KMIV
overnight. Moderate confidence overall, but lower confidence in
timing and thunderstorm potential.

Saturday...IFR ceilings should gradually lift to MVFR and scatter
out to VFR by the late afternoon hours. Isolated showers in the
morning, with scattered showers and thunderstorms possible in
the afternoon. A few storms may be strong to severe. Southwest
wind around 10-15 kt with gusts up to 25 kt possible gradually
shifting to northwest late following a frontal passage. Moderate
confidence.

Outlook...

Saturday night through Tuesday...VFR conditions expected. Gusty NW
winds likely on Sunday.

Tuesday night and Wednesday...Restrictions expected, at least MVFR.

&&

.MARINE...
After midnight, a Small Craft Advisory will be in effect for
all Atlantic coastal waters through Saturday. A Small Craft
Advisory will be in effect for the Delaware Bay beginning at 6
AM Saturday as well. South-southwesterly winds will increase to
around 17-22 kt with gusts up to 25-30 kt possible with seas
building to around 4-6 feet. Scattered rain showers and isolated
thunderstorms are expected after midnight continuing through
the day on Saturday.

Also, patchy to areas of dense marine fog are expected to
develop tonight into Saturday morning. A marine dense fog
advisory may become warranted later tonight, if such fog
develops.

Outlook...

Saturday night and Sunday...At the minimum, SCA conditions expected.
Gusts between 25 to 35 kt possible.

Sunday night through Tuesday...Sub-SCA conditions expected.

Tuesday night and Wednesday...SCA conditions expected.

&&

.FIRE WEATHER...
Showers will impact the area tonight through Saturday evening.
Overall, between 1/4 and 1/2 inch of rain will fall across most
of the area, though up to an inch of rain is possible in the
southern Poconos and far northwest New Jersey, and 1/10 inch or
so is possible in Delmarva.

On Sunday, northwest winds will increase to 15 to 20 mph with 30 to
35 mph gusts possible. In addition, RH values will drop below 40%
south of the PA Turnpike and 195 in NJ. We can`t rule out 30 to
35%.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 6 AM Saturday to 6 PM EDT Sunday for
     ANZ430-431.
     Small Craft Advisory until 6 PM EDT Sunday for ANZ450>455.

&&

$$

SYNOPSIS...Kruzdlo
NEAR TERM...Cooper/DeSilva
SHORT TERM...Kruzdlo
LONG TERM...Kruzdlo
AVIATION...Cooper/DeSilva/Kruzdlo
MARINE...Cooper/DeSilva/Kruzdlo
FIRE WEATHER...PHI