-- Discussion containing changed information from previous version are highlighted. --
658
FXUS61 KPHI 190511
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
111 AM EDT Wed Jun 19 2024

.SYNOPSIS...
Increasing heat and humidity is expected for the rest of the
week into the weekend as high pressure remains offshore and
ridging aloft remains near the area. A back door frontal
boundary is expected to approach and stall near the area by
later Thursday into Saturday, before lifting back northward by
Sunday. A stronger cold front is forecast around Monday of next
week.

&&

.NEAR TERM /THROUGH TODAY/...
-- Changed Discussion --
Only minor tweaks made to the grids early this morning. Forecast
is on track. A quiet but warm night is ongoing.

Through tomorrow, the center of the mid and upper level ridge
will nudge closer to our region. With the surface high
remaining offshore, south to southwesterly winds will push 925
mb temps into the 21-24 deg C range across the region. There
will be little relief overnight with temps only expected to fall
into the mid 60s to low 70s overnight.

By tomorrow, we should have widespread subsidence across the
region, which will act to further suppress any shower
development in our region. Model trends have been slightly lower
with high temperatures tomorrow, but I want to emphasize that
the trend has only been slight. The heat advisory for portions
of the region, still appears on track.
-- End Changed Discussion --

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
Warm conditions continue into Thursday as ridging aloft will
remain in place Wednesday night through Thursday night. A back
door frontal boundary begins to approach the area from the north
later Thursday into Thursday night, while a short
wave/vorticity impulse will approach and move across the area as
well. So there will be a slight chance of showers and
thunderstorms later Thursday into Thursday night, although most
shower activity could dissipate before reaching the area. The
Excessive Heat Watch remains in effect for Thursday, but may
need to be converted to a Heat Advisory depending on the
forecast Heat Index values.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
The Excessive Heat Watch remains in place for Friday through Sunday
as hot and humid conditions will remain in place across much of the
area ahead of the approaching and stalling back door frontal
boundary. Depending on where the boundary sets up, Friday will be a
very hot and humid day for much of the area south of the boundary,
while areas north of the boundary may not be as oppressive. Same
thing for Saturday as the front will likely stall near the area.
Confidence on where the front sets up is low at this time, so we
have kept the Excessive Heat Watch in place where it was before, but
it is possible that some areas will not need to be upgraded. As the
backdoor front approaches and stalls near the area, there will also
be several short wave/vorticity impulses moving across the area as
the flow aloft becomes more zonal. This will allow for a chance of
showers and thunderstorms for much of the area Friday into Saturday.

By Sunday, the back door front will lift back northward, while flow
aloft shifts back to the southwest. This will allow temperatures to
warm back up for all areas again, which will also allow for a lee-
side/pre-frontal/thermal trough to develop across the area. With an
increase in heat and humidity, the Excessive Heat Watch will remain
in place for Sunday. Another concern for Sunday will be increasing
chances of showers and thunderstorms across the area, with the
potential for stronger storms to develop. With the pre-
frontal/thermal trough in place, and west-southwest winds aloft,
instability will increase to 1000-2000 J/kg, while there will be
increasing shear across the area and DCAPE values approaching 1000
J/kg. While we are still several days out, Sunday does have the
potential for strong to severe storms to develop, however confidence
levels in coverage and predictability are low at this time. Heavy
rainfall will also be a concern.

On Monday and Monday night, the actual cold front is expected to
move across the area while additional short wave/vorticity impulses
will move across the area. This will keep a chance of showers and
thunderstorms across the area and warm conditions as well. Some
storms will have the potential to be on the strong side with heavy
rainfall. While some areas will remain quite warm, Monday is not
expected to be as hot and oppressive as Friday through Sunday.

By Tuesday, the front will have pushed through the area an
northwesterly flow aloft will develop. This will allow for dry
weather to return and for the excessive heat to break, at least for
a brief period.

&&

.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...VFR. Winds out of the south around 5 kt. High
confidence.

Wednesday...VFR. Winds out of the south/southwest around 5-10
kt. South/southeast winds later in the day at KILG with wind
funneling up the Delaware Bay and at KACY/KMIV with the sea-
breeze moving through. High confidence.

Wednesday Night...VFR. South/southwest winds around 5 kt. High
confidence.

Outlook...

Thursday-Thursday night...VFR conditions expected. South-
southwest winds 5-10 knots.

Friday-Saturday night...Mostly VFR. Chance of showers and
thunderstorms, especially during the daylight hours. South-southwest
winds 5-10 knots; occasional gusts around 15 knots Saturday.

Sunday...Generally VFR. Chance of showers and thunderstorms.
Southwest winds 10-15 knots, gusts 15-20 knots.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
No marine headlines expected through Wednesday. South winds
around 10 kt this afternoon. Seas 2 to 3 feet.

Outlook...

Wednesday night-Saturday night...Conditions expected to remain below
Small Craft Advisory levels.

Sunday...Winds and waves may increase to Small Craft Advisory levels
during day into Sunday night.

Rip Currents...

Wednesday...South-southeasterly winds will range around 10-20
mph along the coast. Breaking waves in the surf zone are
expected to be around 1-3 feet with a period of 8-9 seconds. For
this reason, have maintained a MODERATE Risk for the
development of dangerous rip currents for Atlantic and Cape May
County Beaches. For the remainder of beaches, went with a LOW
Risk due to winds being more parallel to the shoreline.

Thursday...Similar weather and wave conditions are expected
with a bit more of an onshore component along Ocean County. For
this reason, went with a MODERATE Risk for all New Jersey
beaches except Monmouth County. For the Delaware Beaches and
Monmouth County, continued with a LOW risk of dangerous rip
currents.

Rip currents occur often in the vicinities of jetties and piers.
Utilize any guarded beaches if venturing out into the water. For
specific beach forecasts, visit weather.gov/beach/phi
-- End Changed Discussion --

&&

.CLIMATE...
-- Changed Discussion --
No records were set on Tuesday.

Record high temperatures Wednesday.

Location          Record High (6/19)

Philadelphia, PA      100/1994
Allentown, PA         96/1994
Reading, PA           95/1929
Mount Pocono, PA      86/1929
Trenton, NJ           96/1994
AC Airport, NJ        96/1994
AC Marina, NJ         93/1952
Wilmington, DE        100/1994
Georgetown, DE        96/1952

Record high temperatures Thursday.

Location          Record High (6/20)

Philadelphia, PA      98/1931
Allentown, PA         100/1923
Reading, PA           101/1923
Mount Pocono, PA      89/2012
Trenton, NJ           98/1923
AC Airport, NJ        95/2012
AC Marina, NJ         90/1908
Wilmington, DE        97/2012
Georgetown, DE        98/2012

Record high temperatures Friday.

Location          Record High (6/21)

Philadelphia, PA      99/1923
Allentown, PA         100/1923
Reading, PA           99/1923
Mount Pocono, PA      90/1953
Trenton, NJ           97/1923
AC Airport, NJ        97/1988
AC Marina, NJ         94/2012
Wilmington, DE        98/2012
Georgetown, DE        99/2012

Record high temperatures Saturday.

Location          Record High (6/22)

Philadelphia, PA      100/1988
Allentown, PA         95/1941
Reading, PA           96/1921
Mount Pocono, PA      90/1908
Trenton, NJ           99/1988
AC Airport, NJ        100/1988
AC Marina, NJ         92/1949
Wilmington, DE        98/1988
Georgetown, DE        97/2012

Record high temperatures Sunday.

Location          Record High (6/23)

Philadelphia, PA      97/1888
Allentown, PA         95/1965
Reading, PA           96/1908
Mount Pocono, PA      90/1908
Trenton, NJ           97/1894
AC Airport, NJ        98/1988
AC Marina, NJ         91/1909
Wilmington, DE        100/1894
Georgetown, DE        100/1988
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory until 6 AM EDT Thursday for PAZ054-055-060>062-
     070-071-101>106.
     Excessive Heat Watch from Thursday morning through Sunday
     evening for PAZ054-055-060>062-070-071-101>106.
NJ...Heat Advisory until 6 AM EDT Thursday for NJZ001-007>010-012-
     013-015>020-027.
     Excessive Heat Watch from Thursday morning through Sunday
     evening for NJZ001-007>010-012-013-015>020-027.
DE...Heat Advisory until 6 AM EDT Thursday for DEZ001.
     Excessive Heat Watch from Thursday morning through Sunday
     evening for DEZ001.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Robertson
NEAR TERM...Deal/Hoeflich/Johnson/MJL
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...Hoeflich/Johnson/MJL/Robertson
MARINE...DeSilva/Johnson/Robertson
CLIMATE...NWS PHI