Hail and Damaging Winds in Pennsylvania, April 15, 2025

Area Forecast Discussion
National Weather Service Mount Holly NJ
237 PM EDT Tue Apr 15 2025

.SYNOPSIS...
A strong cold front and upper level disturbance will move
across the area as we head into this evening. High pressure
builds in from the west on Wednesday and then moves offshore on
Friday. A cold front enters the region over the weekend. High
pressure may return for the start of the new week. Another low
pressure may approach the region Monday night and Tuesday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
A strong short wave/vorticity impulse will move across the area
this afternoon, while strong west to northwest flow remains in
the lower levels. This short wave will help create strong lift
across the area, which will combine with an increase in moisture
and allow for isolated to scattered showers, even a few
thunderstorms, to move across the area through this afternoon.
There is not a significant amount of CAPE, but there could be
enough, combined with strong winds aloft to mix down to the
surface to produce some very isolated instances of damaging
winds across portions of eastern Pennsylvania and northern New
Jersey, which is where SPC has a marginal risk of severe
weather. With low freezing levels, there could also be some
small hail associated with the strongest cells.

Another concern through today is the potential for strong
synoptic winds. The pressure gradient remains strong with low
pressure to our north and high pressure to our south. Winds
aloft could mix down to the surface due to steep low level lapse
rates. Wind gusts have already reached 45+ mph in some areas and
this could continue into the remainder of the afternoon.
Therefore we've issued a Wind Advisory through 8 pm.

Any showers or thunderstorms will dissipate by sunset, and the
remainder of the overnight hours will remain dry. Winds will
remain gusty at times in the 20-30 mph range through the night.

On Wednesday, the pressure gradient remains tight across the
area, which will keep gusty winds in place. The winds will not
be as strong as Tuesday, but gusts could still reach 30-35 mph
at times. Partly to mostly cloudy skies can be expected, but no
precipitation is expected on Wednesday.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Fairly quiet through the short term. High pressure will still
be centered to our west Wednesday night, but the pressure
gradient should be relaxing, allowing winds to diminish. Skies
will also start to clear as the upper trough begins pulling out
to the east, so should have better radiational cooling
conditions. This may result in a need for frost/freeze headlines
as temps should be fairly close to freezing across much of the
region except near the water and in the urban centers.

Thursday looks like the sunniest day in some time, with near
wall-to- wall sunshine under mostly clear skies as the high
shifts east just to our south and heights rise rapidly. Still a
bit of a northwesterly breeze but notably lighter than on
Wednesday. Highs should also be significantly warmer, with
either side of 60 across much of the region.

High pressure shifts off the coast Thursday night, with winds
turning a bit more southerly, though becoming quite light after
sunset. The evening will be fairly clear allowing for a quick
drop with radiational cooling, but high clouds increase after
midnight. Thus, expect temps to drop nearly, but not quite as,
cold as Wednesday night, so a little less risk of frost/freeze
headlines.

Friday will feature plenty of clouds as a warm front passes the
region. Over most of our region its likely too dry at the
surface for any rain, but across the far north, some showers are
possible. Highs will continue their upward trend, rebounding
well into the 60s with near 70 possible from Philly south and
west.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The combination of warm frontal passage and increased cloud
cover plus southerly wind will keep Friday night much milder
than Thursday night, with most areas staying above 50. Some
parts of the Delmarva might not fall below 60. With the front
well clear and forcing not present, it should stay dry.

Next cold front approaches from the northwest on Saturday and
enters the region Saturday night. This is the last day of the
forecast for which we have reasonable consistency in guidance,
with temps well into the 70s, perhaps 80 in spots, along with an
increasing risk of a shower or t-storm later in the day or at
night.

After Saturday night, a great deal of uncertainty has crept
into the forecast. The latest guidance is more uncertain with
how far this front can push southward, though prior modeling
suggested it would clear the region by Sunday. For the time
being have mostly kept with the previous thinking, with a drier
but much cooler Sunday and Monday with highs 10-15 degrees
lower, but no chance of precip. However, as hinted, if the front
ends up hung up across the region for a few days, temps may be
considerably milder, but with a lingering chance of showers and
t-storms for Sunday and Monday. Another wave may then pass
Monday night which could finally clear the inclement weather
from the region by Tuesday. Bottom line though is that the
forecast beyond Saturday night has low confidence.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Rest of Today...Mainly VFR ceilings. Isolated to scattered
showers will continue through this afternoon, which may briefly
lower visibilities, so we have included a PROB30 for showers and
6SM. There is even a chance of an isolated thunderstorm, but
have kept them out of the TAFs for now due to limited nature.
Most likely window would be 19z-23z. Winds will gust out of the
west 30-35 knots, occasional peak gusts around 40 knots.
Moderate confidence.

Tonight...VFR conditions prevail through the night. Winds
continue to gust 20-30 knots. High confidence.

Wednesday...VFR conditions expected. Winds gust 25-30 knots.
High confidence.

Outlook...
VFR conditions should prevail Wednesday night through Friday
night. Sub-VFR possible Saturday and Saturday night with
potential showers and thunderstorms with a passing cold front.
VFR likely returns Sunday.

&&

.MARINE...
A Gale Warning has now been issued for all waters as winds are
expected to increase later this afternoon into this evening to
35-40 knots. Winds will lower below Gale force later tonight,
and remain above Small Craft Advisory levels through Wednesday.

Outlook...
Conditions generally subside below SCA criteria Wednesday night
and should remain below criteria through Thursday night.
Southwesterly winds increasing ahead of a cold front then bring
SCA conditions back to the region Friday through Saturday, with
gusts up to 30 kts and seas up to 6 feet with popssible showers
and even a stray thunderstorm. Conditions start to subside below
SCA levels Sunday.

&&

.FIRE WEATHER...
RHs may be below 30 percent during the afternoon Thursday with
winds gusting 20-25 mph in the afternoon under plenty of
sunshine. This may result in fire weather concerns depending on
fuel conditions. RHs should improve for Friday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Wind Advisory until 8 PM EDT this evening for PAZ054-055-
     060>062-070-071-101>106.
NJ...Wind Advisory until 8 PM EDT this evening for NJZ001-007>010-
     012>027.
DE...Wind Advisory until 8 PM EDT this evening for DEZ001>004.
MD...Wind Advisory until 8 PM EDT this evening for MDZ012-015-019-
     020.
MARINE...Gale Warning until 2 AM EDT Wednesday for ANZ430-431-450>455.

&&

SYNOPSIS...RCM
NEAR TERM...MJL/Robertson
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...RCM/Robertson
MARINE...RCM/Robertson
FIRE WEATHER...RCM