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000
FXUS61 KPHI 131712
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
112 PM EDT Sat Apr 13 2024

.SYNOPSIS...
A secondary cold front will cross the region early this morning as
an area of low pressure will move into eastern Canada. High pressure
will briefly build into the region today before an area of low
pressure passes to the north of the region and drags a cold front
across the Mid-Atlantic region Sunday night. High pressure builds
back in Monday into Tuesday, before a series of frontal boundaries
and low pressure systems affect the east coast Wednesday through
Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
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Forecast is on track this afternoon. No changes to the grids
overall.

The primary concern through the day today is the windy
conditions. Although the low will be gradually moving further
away from our region through the day, we`ll keep both a tight
surface pressure gradient and low level height gradient over our
region especially as a high builds in from the southwest. Based
on the latest guidance, it still appears that most of the
region should see wind gusts in the 35 to 40 mph range, which is
just below wind advisory criteria. The exception is in portions
of eastern PA, where some gusts to 45 mph are possible,
particularly in the Berks County and Lehigh Valley area. A wind
advisory has been issued for portions of southeastern PA. May
see slightly more wind damage than we would typically with wind
gusts to 45 mph given the wet ground.

With the high building in, we should see precipitation end from
south to north through the day, as well as clearing skies. Winds
may be a bit slow to diminish this evening and overnight, which
could be a blessing in preventing widespread frost for most of
the region (with the exception of the southern Poconos and
northwest NJ.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
The start of the new week will bring a return of chances for showers
and thunderstorms after the brief respite Saturday/Saturday night. A
surface low will be moving east-southeast out of the Great Lakes and
into the Northeast, passing just to the north of our region. The
warm front associated with this system will push through the region
Sunday morning, though no precipitation is expected with this
frontal passage.

With the region now in the warm sector, temperatures and dew points
will begin to rise fairly rapidly, into the low-mid 70s and upper
40s respectively by mid-afternoon. In the mid-levels though, the
better dynamics look to be lagging behind slightly with the peak 700-
500 mb lapse rates and strongest LLJ arriving later in the evening.
Once the LLJ is in place, there would be a threat for severe wind
gusts being mixed down with any stronger thunderstorms and SPC has
highlighted the western half of the region in a MARGINAL risk as a
result. Shower and thunderstorm activity will be on the downward
trend heading into the overnight hours though which keeps the
overall potential low. The cold front will then pass through the
region and temperatures will fall into the mid to upper 50s.

Conditions dry out on Monday as high pressure begins to build into
the region. Temperatures Monday afternoon look to be rebound into
the low-mid 70s before falling into the 40s/low 50s Monday
night.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The start of the long-term period looks to be dry as high pressure
continues to move through the region on Tuesday. High temperatures
look to be in the low-mid 70s once again across most of the region.

Heading into Wednesday and continuing through the end of the work
week, the forecast becomes decidedly wetter. A pair of expansive
upper-level lows will be slowly transiting across the north central
United States and eastern Canada. This action will bring several mid-
level waves to the Eastern Seaboard and provide ample opportunities
for showers or a few thunderstorms to develop and move through the
area. As of now, the most organized of these waves looks to move
through the region Wednesday-Wednesday night and the highest PoPs of
the long term period (55-65%) are in this period to reflect that.
Overall though, it is still a bit premature at this time to say any
particular day through the back half of the week will be a complete
washout. High temperatures through the end of the work week remain
near to above normal in the mid 60s-mid 70s.

&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Rest of Today...VFR. Westerly winds of 20-25 kt with gusts up
to 35-40 kt possible through the early evening. Highest gusts at
KRDG. Moderate confidence.

Tonight...VFR with mostly clear skies. Westerly winds of 10-20
kt early diminishing to 5-10 kt by 06Z, gradually backing and
becoming southwesterly. High confidence.

Sunday...VFR through the early afternoon. Winds increase by late
morning, out of the southwest, around 10-15 kt, gusting 20-25
kt. Some showers and scattered thunderstorms move in during the
late afternoon/early evening, mainly west of the I-95 corridor.
Sub-VFR conditions possible around that time (around 30-40%),
especially at KRDG/KABE, with prevailing VFR otherwise. Moderate
confidence overall.

Outlook...

Sunday Night...Any sub-VFR conditions will lift to VFR once the
cold front comes through.

Monday and Tuesday...VFR conditions expected with fair weather.

Wednesday...Sub-VFR conditions possible (30-40%) with showers.
-- End Changed Discussion --

&&

.MARINE...
The gale warning remains effect for the coastal waters and
Delaware Bay. Gusts at or just above 35 kt are expected a times
through the late afternoon. Winds wind down back to SCA levels
by Saturday evening and then sub- SCA overnight, with waves
dropping to 2-4 ft by late night as well.

Outlook...

Sunday...Small Craft Advisory conditions expected.

Monday and Tuesday...Sub-SCA conditions expected.

Wednesday...SCA conditions possible (40-50%).

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Wind Advisory until 6 PM EDT this evening for PAZ054-055-
     060>062-101>103-105.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning until 6 PM EDT this evening for ANZ430-431-
     450>455.

&&

$$

SYNOPSIS...AKL
NEAR TERM...Hoeflich/Johnson
SHORT TERM...AKL
LONG TERM...AKL
AVIATION...AKL/Hoeflich/Johnson
MARINE...AKL/Johnson