242
FXUS61 KPHI 032231
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
631 PM EDT Fri May 3 2024

.SYNOPSIS...
High pressure over New England will maintain an onshore flow
through the next few days. A series of cold fronts approaches
from the west through the weekend, with the second (and
stronger of the two) front stalling out nearby by early next
week. The stalled front lifts north as a warm front at some
point in the Tuesday/Wednesday timeframe, bringing a return to
above normal temperatures.

&&

.NEAR TERM /THROUGH SATURDAY/...
6:30PM...The current forecast continues to remain challenging
due to pesky marine layer over the Coastal Plain. An expansive
ridge of high pressure is building into eastern Canada with the
southwestward periphery of this feature extending back into the
Mid-Atlantic. In fact guidance actually depicts this feature
strengthening slightly over our area during the next 24 hours.
Meanwhile though, this ridge has resulted in easterly flow that
has brought in a low deck of some marine stratus into much of
NJ, DE, and even extending at times into portions of eastern PA.
Finally, there is a frontal system that`s approaching from the
west with some showers however, it will take some time for
these showers to get into the area over the weekend as it runs
up against the ridge in place. The upshot of all this is that
skies are variable across the area with the marine stratus
eroding back to the east while high cirrus continues over
western areas.

Regardless, it will remain precip free though through the
evening. Overnight, however, shortwave energy will ride over the
top of the upper level ridge centered over the east and help to
push showers from the west closer to the region. This could
bring a few light showers into parts of Delmarva and eastern PA
by daybreak. Otherwise, clouds thicken through the night with
lows getting down mainly into the upper 40s to around 50.

For Saturday, low pressure moves eastward towards the Great
Lakes driven by an advancing upper level trough. As this occurs,
showers well ahead of it will continuing to try making inroads
into our area while running up against the stubborn surface high
that will be slow to move out. The upshot is some scattered
showers will likely make it in at times, especially over eastern
PA and Delmarva and especially getting into the second half of
the day (POPs here by late day generally 40 to 60 percent).
Otherwise it will be a mostly cloudy and cool day with
continuing easterly winds and highs only making it to the upper
50s to low 60s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Saturday night will featured continued marine flow from the east
as the approaching front from the west washes out. Thus, expect
areas near the coast to be mostly dry and cool, with a better
chance of showers inland due to the nearby stalled front. Lows
mostly in the upper 40s.

Next, stronger front approaches from the west Sunday, but its
approach looks slower, so have slowed the progress of higher
POPs into the area. Looks like best chance of widespread showers
is late day and at night Sunday night. With the marine layer
likely to hold fairly firm, chance of thunder looks minimal, and
severe weather risk appears zero. Highs 50s north, 60s south,
perhaps near 70 far southern DE and adjacent parts of MD.

Rain showers move out on Monday morning, though again opted for
slower timing given trend. Marine layer looks like it is at
least somewhat disrupted as flow turns westerly and a warm front
tries to lift north, allowing temps to potentially rise to the
70s for most and near 80 southern DE/adjacent MD. Guidance now
wants to generate some convection in the afternoon, and given
the warmer and more humid air mass, its not out of the question
we have a few stronger cells, but at this point there doesn`t
appear to be a significant severe wx or flood risk.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Unsettled weather continues through the week ahead. The front
that lifts north thru the area Monday doesn`t get far, and looks
to even slide back south a little Tuesday, though at this point
still looks likely mostly 70s. Another approaching shortwave and
proximity of the front could spark off a shower or t-storm, but
right now looks like low coverage.

Front lifts a little further north behind that shortwave
Wednesday, allowing temps to rise a bit. With it remaining
nearby and another front approaching from the north, the odds of
some aft/eve convection increases a bit. Highs closer to 80.

Guidance is trending towards the return of a marine layer behind
said front for Thursday and Friday, with a cooling trend in
temps. A passing wave may produce some better shower coverage
Thursday as well, so we have highest POPs in the long term on
Thursday. Friday trend is a little drier but still a marine
influence.

It should be noted that with the wavering front nearby all week
and several weak waves, its possible the details of the forecast
are notably different from how they currently appear, so check
back for updates frequently. Guidance is very mixed presently.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through this afternoon...Mainly MVFR predominating at ACY, MIV,
TTN, and PNE due to low stratus. Otherwise mainly VFR with a
scattered deck around 2500 feet. East winds 10 to 15 knots with
some gusts to around 20 knots possible. Moderate confidence.

Tonight...The marine stratus should result in MVFR cigs or lower
eventually predominating by the overnight period with conditions
lowering through the evening around PHL but likely not until the
overnight at RDG and ABE. IFR cigs likely overnight at MIV and
ACY. East winds 5 to 10 kt. Low confidence.

Saturday...Mainly MVFR in the morning with some improvement in
the afternoon to VFR except at MIV and ACY where MVFR may
continue. East winds around 10 knots. Low confidence.

Outlook...

Saturday Night through Sunday Night...Restrictions expected
with showers moving through, with CIGs as low as IFR possible.
Best chance of showers is late Sunday/Sunday night.

Monday through Wednesday...Primarily VFR though some
restrictions possible with any showers. 20-40% chance of showers
through this period.

&&

.MARINE...
The Small Craft Advisory has been extended for the ocean zones
from Great Egg Inlet to Fenwick Island until 10 PM due to seas
around 5-6 feet. These conditions should continue to diminish
early this evening with seas diminishing to 10 to 15 knots and
seas around 3 to 4 feet. Little change is expected on Saturday.
It will also be mainly cloudy over the waters through Saturday
with some patchy fog possible at times.

Outlook...

Saturday night through Wednesday...No marine headlines
anticipated. Showers/thunderstorms possible on the waters Sunday
through Sunday night.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 10 PM EDT this evening for
     ANZ453>455.

&&

$$

SYNOPSIS...Fitzsimmons/Hoeflich/RCM
NEAR TERM...DeSilva/Fitzsimmons/MPS
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...Fitzsimmons/MPS/RCM
MARINE...DeSilva/Fitzsimmons/MPS/RCM