578
FXUS61 KPHI 181741
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
141 PM EDT Tue Jun 18 2024

.SYNOPSIS...
Surface high pressure southeast of New England will slide south
on Wednesday and will remain anchored offshore into next
weekend. A cold front will pass through the region early next
week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
For this afternoon, isolated showers may encroach on the
southern Poconos as we have already seen, but for most of the
region, continued hot and dry conditions.

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.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Almost 600 dam 500 mb high will be over the Northeast on
Wednesday as 1030 mb surface high pressure will be some 500 or
so miles east of Nantucket Island. 850 mb temperatures will
range from 16C to 18C, which yields surface high temperatures in
the low to mid 90s across most of northern New Jersey and
southeast Pennsylvania, and generally in the upper 80s for
Delmarva and southern New Jersey. These high temperatures have
trended cooler by a couple of degrees compared to previous
forecast. In addition, humidity levels will not be quite as
high, as surface dew points will generally be in the lower 60s.
This results in max heat index values in the low to mid 90s.
Although these values may fall just short of Heat Advisory
criteria, it will be the second day of several days of prolonged
heat and humidity, so the effects of the heat will be
exacerbated. Will go ahead and convert the Excessive Heat Watch
that was in effect for Wednesday to a Heat Advisory for most of
New Jersey, southeast Pennsylvania, and northern Delaware.

On Thursday, the 500 mb high slides south into the Mid-Atlantic
while the offshore surface high slides to about 600 miles or so
southeast of Atlantic City. Winds shift to more of a southwest
flow compared to Wednesday, and this will tap into somewhat
warmer and more humid air. Both high temperatures and surface
dew points will be a few degrees higher on Thursday compared to
Wednesday. Max heat index values will be in the mid to upper 90s
for most of the area, and around 100 for portions of the I-95
corridor in New Jersey. Will keep the Excessive Heat Watch in
effect. Some shortwave energy passing through Pennsylvania and
central New York may touch off some afternoon showers and
thunderstorms in the southern Poconos. Will cap PoPs at slight
chance.

At night, Wednesday night will generally be in the mid to upper
60s, and it will be muggy with patchy fog developing away from
the urban centers. Thursday night will be warmer and a bit more
humid with lows in the upper 60s to low 70s.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
500 mb high sags into the Midwest and Gulf Coast states on Friday,
and then down into the Southern Plains on Saturday. Meanwhile,
offshore surface high becomes a Bermuda high through the weekend. As
a result, hot and weather continues through the weekend.

The heat and humidity build into the region for the end of the week
and weekend. Highs on Friday will be in the mid to upper 90s,
possibly touching 100 along the I-95 corridor. With surface dew
points in the upper 60s to around 70, max heat index values will
range from 100 to as high as 110. On Saturday and Sunday, highs will
be a few degrees cooler, generally in the low to mid 90s, but
surface dew points will now climb into the lower 70s. This will keep
max heat index values from 100 to 105. Will go ahead and extend the
Excessive Heat Watch into Sunday.

Several mid-level disturbances will pass north of the region Friday
and Saturday, and this may touch off afternoon and evening showers
and thunderstorms. Will follow the NBM and keep PoPs capped at
chance, mainly for the northern areas.

Cold front then approaches and passes through the region late
Sunday and Sunday night. This will touch off scattered showers and
thunderstorms across most of the area, which may linger into
Monday. Monday turns, well, it is hard to say "cooler" as highs
will be in the upper 80s to around 90, which are still above
normal. So the best way to say it will be, "Not as hot".

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Through Tonight...VFR. Isolated -TSRA northwest of KABE possible
through 03Z. Winds varying between SSE and SSW. Wind speeds 10
kt or less.

Wednesday...VFR with few if any clouds. Winds predominantly S at
10 kt or less.

Outlook...

Wednesday Night through Thursday...VFR.

Friday through Saturday...Predominantly VFR, but scattered
SHRA/TSRA possible each afternoon and evening.

&&

.MARINE...
No marine headlines expected through Wednesday. South winds 10
to 20 knots this afternoon. Winds will gust around 20 knots,
especially right along the beaches and in the backbays. Farther
offshore, there will likely be enough of an inversion to limit
mixing and stronger gusts.

We haven gotten reports of higher waves in the area of some
inlets. Based on surrounding observations and coastal web cams,
it looks as if this may be confined to the inlets, so have held
off on issuing any SCA, but will continue to monitor to see if
it becomes more widespread.

Outlook...

Wednesday through Saturday...Winds and seas should generally
stay below SCA criteria. However, winds on northern NJ ocean
waters will increase to 15 to 20 kt and gusts may approach 25 kt
each afternoon.

Rip Currents...

Through Wednesday, southerly winds of 10-20 mph along the coast with
some enhancement from sea breeze circulations. Breaking waves in the
surf zone are forecast to be around 2 feet, however there looks to
be some longer period swell energy rolling in. Given the southerly
wind component intersecting more of the New Jersey coast, went with
a MODERATE risk for the development of dangerous rip currents both
Tuesday and Wednesday for all locations except Monmouth county where
like the Delaware Beaches the winds will be more parallel and
therefore a LOW risk.

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

&&

.CLIMATE...
Record high temperatures Tuesday.

Location          Record High (6/18)

Philadelphia, PA      96/1957
Allentown, PA         95/2018
Reading, PA           97/1957
Mount Pocono, PA      88/1957
Trenton, NJ           96/1957
AC Airport, NJ        95/2014
AC Marina, NJ         94/2014
Wilmington, DE        95/1957
Georgetown, DE        97/2014

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

&&

.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...MPS
NEAR TERM...Deal/Johnson
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...Johnson/MPS
MARINE...Johnson/MPS
CLIMATE...