200
FXUS61 KPHI 040147
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
947 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 TODAY/...
9:45PM...The biggest change to the forecast was made to reflect
ongoing conditions for the next several hours. The marine
stratus has continued to dwindle over the area tonight, now only
confined from around Philadelphia and across the Delmarva.
Elsewhere, just some higher clouds remain to at times clear
skies. As a result, have updated sky grids and also noted
potential marine fog tonight (mentioned in marine section
below). Otherwise, forecast remains on track with the previous
discussion below:

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

Tonight...Different conditions expected for each terminal
tonight. For KRDG/KABE, expect VFR through 05-06Z, before
becoming MVFR CIGs after 07-08Z. For KTTN/KPNE/KPHL/KILG,
expect a mixture of VFR/MVFR CIGs through 07-08Z, before
becoming MVFR CIGs after 08-09Z. For KMIV/KACY, expect MVFR CIGs
through 05-06Z, becoming IFR CIGs after 06Z. East winds around
3-8 kt. Low confidence, especially with the timing of lowering
ceilings.

Saturday...Mainly MVFR for all terminals. There is indication a
brief period of VFR CIGs are possible during the afternoon for
all terminals except KMIV/KACY. Otherwise, just some scattered
showers. East-Southeast winds around 8-13 kt. Moderate
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 Cape May to Fenwick Island until midnight due to seas
around 5-6 feet. These conditions should continue to diminish
through the overnight hours with winds diminishing to 10 to 15
knots and seas around 3 to 4 feet. Little change is expected on
Saturday. There is the potential for some dense marine fog
early Saturday morning especially south of Little Egg Inlet,
otherwise, just mostly cloudy skies are expected.

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 midnight EDT tonight for ANZ454-455.

&&

$$

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