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253
FXUS61 KPHI 050129
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
929 PM EDT Sat May 4 2024

.SYNOPSIS...
Stationary boundary keeping the region unsettled today lifts
northwards as a warm front tonight and Sunday. Cold front
approaches Sunday night into Monday looking to cross through
later Monday/Monday night. Cold front becomes nearly stationary
over the region for Tuesday/Wednesday/Thursday, keeping things
unsettled. Another cold front looks to come through between the
Thursday night and Friday night time frame.

&&

.NEAR TERM /THROUGH TODAY/...
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9:20pm...Latest radar imagery shows a batch of light rain over
NE PA and N NJ lifting northward towards New York. Elsewhere,
just some light showers are ongoing. The general trend for the
remainder of tonight is that there should be a lull in activity
overnight, but there will still be some showers especially over
our western areas. The further east you are, the rain chances
overnight decrease. Lows will be in the mid 40s to low 50s.

Surface analysis depicts a backdoor front sinking south across
North Carolina while a cold front is moving southeast from
Canada. Another cold front is pushing southeast across the
western Great Lakes and north/central Plains. Aloft, a ridge
straddles our region north to south, but several weak shortwaves
are located over the upper Ohio Valley and southeastern US,
with more further west over the central Plains.

Weak warm advection above the cool marine layer will allow
showers to continue through Sunday, but the main mid and upper
level forcing will remain mostly to our west in central PA.
Thus, expect relatively dry conditions near the immediate coast,
with the bulk of precip near Chesapeake Bay and across western
Chester, Berks and the Poconos through Sunday afternoon. That
said, enough shortwave energy finally pushes eastward over the
region by then to allow more organized showers to cross much of
the remainder of the region, so have POPs maxing out Sunday
afternoon. QPF looks relatively light given the long duration
as well, with less than an inch area-wide and less than a half
inch from I-95 corridor on south and east, with almost nothing
near the coast. All that being said, it still won`t be very
nice, as the persistent easterly flow will keep skies cloudy and
temps cool with 50s and 60s during the day. The warm front does
try to lift northward late on Sunday, so that gives areas from
Philly south the opportunity to approach (but not reach) normal,
but it`ll be a struggle.
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&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...
Unsettled conditions persist Sunday night as a cold front from
the west approaches. Cold front will be rather slow getting
here, still approaching our region Monday and crossing through
perhaps either later Monday or Monday night. Thereafter,
guidance suggests the cold front may stall over or close by the
region Monday night into Tuesday.

Given this synoptic situation, an unsettled short term looks to
be on the horizon. Though unsettled, the short term will not be
all that impactful, just showery in general. Precipitation will
not amount to much across the region during the term, maybe
0.25 inches at most. Our region is not currently outlooked by
the WPC for any excessive rainfall or the SPC for any severe
weather. Likely and categorical PoPs Sunday night will diminish
with time, mainly chance PoPs for the periods thereafter.

Great support from model soundings for fog/low stratus development
Sunday night; PBL should be nice and saturated, RHs 90-100%.
Some lighter and less impactful fog development is possible for
some areas Monday night, but much less support from model
soundings for this period is noted.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
Once again, an unsettled and showery forecast looks to be tap for
the long term. Cold front forecast to come through the region Monday
into Tuesday is likely to stall over or close by thereafter,
becoming a stationary front. Though this boundary may lift a
little northwards some with time (resembling a warm front), the
boundary will remain stationed over the region for
Tuesday/Wednesday/Thursday, perhaps even into the Thursday
night time frame. Another cold front looks to approach
Thursday/Thursday night, but when the cold front comes through
at this point is not uncertain. Cold front could cross through
anytime between the Thursday night and Friday time frame.
Weakness in the upper-levels will be present during the long
term; this adds a great deal of uncertainty in the timing of
features and synoptic progression.

Forecast will include mainly chance PoPs through all the periods of
the term. Not really seeing anything too impactful to draw
attention to at this point (i.e., severe weather or excessive
rainfall). Temperatures look to run above average through much
of the term.

&&

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

Tonight...A mixture of VFR/MVFR ceilings until around 02-03Z,
before eventually lowering to MVFR/IFR ceilings thereafter.
Temporary visibility restrictions in scattered rain showers.
East winds around 5-10 kt. Moderate confidence, but lower
confidence with regard to timing of lowering CIGs.

Sunday...Anticipate IFR conditions most of the day, however
there may be some brief lifting up to MVFR during the afternoon.
Rain showers likely. East-Southeast winds around 8-15 kt.
Moderate confidence.

Outlook...

Sunday night through Thursday...Mainly sub-VFR with chances for
SHRA during most periods. A few periods may see VFR conditions
return.

&&

.MARINE...
No marine headlines in effect through Sunday. Ocean waves 2-4 ft
with easterly winds 10-15 kt and a few gusts up to 20 kt.
Intervals of reduced vsby in spotty showers.

Outlook...

Sunday night through Wednesday night...No marine headlines
anticipated. Mostly cloudy with chances for showers.

Thursday...SCA flag possible. Seas may build to 5 feet in some
locations, wind gusts increase to 20-25 kts. Chance of showers
(40-60%).

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Wunderlin
NEAR TERM...DeSilva/RCM
SHORT TERM...Wunderlin
LONG TERM...Wunderlin
AVIATION...DeSilva/RCM/Wunderlin
MARINE...RCM/Wunderlin