-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 130850
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
450 AM 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/...
Through Saturday morning, will continue to see isolated to
scattered showers move through the region as the intense surface
low remains over Quebec and the secondary trough/cold front
continues to approach our region. For the most part it will be
rain, but in the higher elevations of the Poconos it could be
cold enough for some snow to mix in, especially around day break,
but little if any accumulation is expected.

The primary concern through the day on Saturday 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.

&&

.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 /09Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Through 12Z...Prevailing VFR conditions expected, but periods
of MVFR ceilings and visibilities possible, especially with any
shra. The highest risk for MVFR restrictions looks to be at
KRDG, KABE, and KTTN. SW-W winds of 10-20 kt with gusts up to
25-30 kt possible after frontal passage late. Moderate
confidence overall, but lower confidence with regard to ceilings
lowering.

Today...Prevailing VFR, though there may be localized MVFR
ceilings, especially at KABE and KTTN. W-NW winds of 20-25 kt
with gusts up to 35-40 kt possible in the afternoon. Moderate
confidence.

Tonight...VFR with mostly clear skies. W-NW winds of 10-20 kt
early diminishing to 5-10 kt by 06Z. High confidence.

Outlook...

Sunday...Sub-VFR conditions possible (30-40%) with scattered showers
and thunderstorms.

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

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

&&

.MARINE...
-- Changed Discussion --
Gale conditions have developed a few hours and slightly further
south than previously forecasted. Therefore, the gale warning
has been put into effect and has been expanded to include the
Atlantic coastal waters off the coast of Delaware. 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%).
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
All coastal flood advisories have been dropped as of 11 PM this
evening. Water levels along the back bays of Ocean County NJ,
mainly around northern Barnegat Bay, may still see some spotty
minor flooding, but it does not look like enough to prompt an
advisory.

Meanwhile, the forecast for the tidal lower Delaware River has
been challenging. Just as it looked tidal anomolies were going
to clearly allow water levels to reach advisory thresholds for
Saturday morning`s high tide, those anomolies have lowered
by nearly a half-foot this evening. Now expect Burlington may
see some very brief spotty minor flooding, but otherwise not
enough to justify keeping the advisory that was issued earlier
on Friday for the Saturday morning high tide.

Heading through the rest of the weekend, with both astronomical
tides lowering and continued runoff and drainage of the rivers
and bays out to sea, the coastal flood threat will finally end.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

$$

SYNOPSIS...AKL
NEAR TERM...Johnson
SHORT TERM...AKL
LONG TERM...AKL
AVIATION...AKL/Johnson
MARINE...AKL/Johnson
TIDES/COASTAL FLOODING...WFO PHI