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000
FXUS61 KPHI 141103
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
703 AM EDT Sun Apr 14 2024

.SYNOPSIS...
High pressure will briefly be in control through this morning before
an area of low pressure passes to the north of the region and drags
a cold front across the Mid-Atlantic region tonight into Monday.
High pressure builds back in by late Monday into Tuesday,
before a series of frontal boundaries and low pressure systems
affect the east coast Wednesday through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 700am...The forecast for today remains largely unchanged.
The entire area will get into the warm sector, with
temperatures getting into the upper 60s and low to mid 70s. A
cold front will approach from the northwest, with showers and
thunderstorms developing out ahead of it, taking on a linear
mode. The highest instability will be to our west, though with
good forcing and relatively high shear, especially in the low-
levels, some organized convection will likely make it into our
area. The limiting factor is the instability over our region,
roughly 300-500 J/KG of MUCAPE. The steepest lapse rates will
also be well ahead of the better dynamics. Most of the CAM
guidance also has the line of storms coming in right around
sunset or even later.

Overall, everything really isn`t lining up perfectly for a
widespread severe event, and the thinking is that it will be more
localized due to the relatively limited instability. The Storm
Prediction Center now has a SLIGHT risk for the southern
Poconos and portions of the Lehigh Valley and northwest New
Jersey. The threat diminishes significantly the further south
you go as guidance has the line fizzling rather quickly once the
sun goes down. Delmarva and far southern New Jersey actually
will likely stay dry. The main threat is damaging wind gusts as
a 50-60 kt low level jet will be overhead around the time the
line of storms make it to our area which could mix down with any
stronger storms. Cannot rule out a tornado as well with good
low-level shear and SRH in the 0-1 km layer.

The cold front passes overnight and any showers should dissipate by
midnight or so. Temperatures will drop into the 50s overnight with
upper 40s in the Poconos/northern New Jersey.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
The main forecast challenge for Monday will be a cold front that
will still be our vicinity. There is some uncertainty regarding how
quickly it will move through with the NAM and GFS clearing it south
through the area Monday morning into the early afternoon while the
GEM Regional is several hours slower. The upshot of this is that we
did add in a 20 percent chance of showers and thunderstorms for
Monday afternoon for our Delmarva Counties into southern NJ as these
areas will be the last to see the front clear and so will have at
least a slight chance of seeing some afternoon convection. It will
be another warm day with most areas seeing highs in the 70s except
cooler near the coast and over the southern Poconos.

High pressure builds in for Monday night and Tuesday bringing fair
weather under mainly clear to partly cloudy skies. Lows Monday night
will be mainly in the 40s to low 50s with highs Tuesday mainly in
the low 70s except once again cooler right near the coast and over
the southern Poconos. The high will start to retreat to our north
and east as we head into Tuesday night as the front to our south and
west starts advancing back towards the area as a warm front. This
will bring an increase in cloud cover with a few showers possible by
Wednesday morning, especially over Delmarva into SE PA.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
In the big picture, the weather pattern will become more unsettled
once again as a large upper level trough with a closed off low
gradually moves eastward from the Canadian Prairies into into Ontario
and Quebec through the mid to late week period. An associated
surface low will also consolidate over the Great Lakes region and
then move into northern Ontario during this period. This will put
our area in a moist deep layer SW flow which will overrun a frontal
boundary at the surface that will remain stalled near Delmarva much
of this period. The upshot of this is that it will be mostly cloudy
with chances for rain/showers each day Wednesday through Friday. The
best chances for widespread showers look to be late Wednesday into
early Thursday and it is for this time period where we have likely
POPs in the forecast. The cloud cover and showers will keep it
cooler compared to this weekend and earlier in the week although
temperatures will actually be fairly close to average.

The upper level trough with its associated frontal system at the
surface should finally swing through the area Friday night into
Saturday with one final round of showers before there should be a
drying trend through next weekend.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Sunday...VFR expected at all terminals. Light SW winds early
around 5-10 kt will increase by 14-15Z around 10-15 kt with
gusts reaching up to 25-30 kt through the afternoon. Some
showers and scattered thunderstorms are anticipated to move in
during the late afternoon/early evening, mainly for KRDG/KABE.
Sub-VFR conditions are possible within any thunderstorm that
does occur. Any lingering sub-VFR conditions Sunday night will
lift to VFR once the cold front comes through. Moderate
confidence overall.

Outlook...

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

Wednesday and Wednesday night...Sub-VFR conditions possible (30-40%)
with showers. SSE winds around 10 kts to start, gradually increasing
to 15 kts by late afternoon with gusts up to 20 kts at night.

&&

.MARINE...
Winds and seas will remain below SCA criteria for all Atlantic
Ocean coastal waters until this afternoon when wind gusts and
seas will increase once again to 25-30 knots and 5-7 feet
respectively. As a result, an SCA has been issued beginning at
2 PM EDT this afternoon and continuing through tonight until
early Monday morning.

For the Delaware Bay, sub-SCA conditions are expected through
Sunday night.

Outlook...

Monday and Tuesday...Seas may still be near 5 feet early in the day
Monday but otherwise sub SCA conditions expected for this
period.

Wednesday and Wednesday night...Winds and seas gradually build as
the next storm system approaches. SCA conditions possible by
Wednesday night.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 2 PM this afternoon to 8 AM EDT
     Monday for ANZ450>455.

&&

$$

SYNOPSIS...AKL/Fitzsimmons/MJL
NEAR TERM...AKL/DeSilva/Hoeflich
SHORT TERM...Fitzsimmons
LONG TERM...Fitzsimmons
AVIATION...AKL/Fitzsimmons
MARINE...AKL/Fitzsimmons