817
FXUS61 KPHI 150847
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
447 AM EDT Mon Jul 15 2024

.SYNOPSIS...
Bermuda high pressure remains offshore through the middle of
the week. A thermal trough looks to develop east of the
Appalachians Monday and Tuesday. Excessive heat and humidity are
expected through Wednesday along with daily thunderstorm
chances. A cold front will cross the region Wednesday night into
Thursday, stalling out and lingering near or just south of the
area through the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Some weak shortwave energy touched off some showers producing
locally heavy rain over portions of northern New Jersey. Will
add some chance PoPs for portions of northeast New Jersey for
the next couple of these showers until they move out of the
area. A few rumbles of thunder are possible.

Bermuda high pressure will usher an increasingly hot and humid
airmass into the region today.

Patchy fog across the area will lift and dissipate shortly
after sunrise this morning, giving way to mostly sunny skies.
High temperatures today will soar into the mid and upper 90s for
most of the area, except for the mountains and along the
immediate shorelines, where highs will be in the 80s. Surface
dew points start out in the low to mid 70s. West winds will
increase to 10 to 15 mph with occasional gusts up to 20 mph, and
along with those mostly sunny skies, there should be enough
mixing in the afternoon for those dew points to drop back to
around 70, and possibly even in the upper 60s, during peak
heating of the day. This will still yield max heat index values
of 100 to 105. No changes will be made to the Heat Advisories
and Excessive Heat Warnings that were in effect for today.

There is another threat for severe weather late this afternoon
and into this evening. An MCS currently over the Great Lakes and
Ohio Valley will track east today and will move into western
New York and western Pennsylvania by this afternoon. With some
troughiness and shortwave energy approaching from the west, this
will trigger another round of late day showers and
thunderstorms. For most of the area, PoPs will be capped at
chance, but will introduce likely PoPs for the southern Poconos
towards this evening. With the heat and humidity, SB CAPE values
will be upwards of 1500 to 2000 J/kg. BUFKIT soundings
indicating an inverted-V pattern along with fairly steep low
level lapse rates. Also, PWATs will be almost 2 inches. Damaging
wind gusts, frequent cloud to ground lightning strikes, and
heavy rain will once again be the threats.

Showers and thunderstorms taper off after sunset. Another warm
and muggy night on tap with lows in the 70s. Patchy fog may
develop once again along the coasts and in areas where heavy
rain develops later today.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
The excessively hot and humid stretch continues through Tuesday
and Tuesday night. For Tuesday, temperatures increase even more
along with lower chances for convection during the daytime
period. Tuesday is still expected to be the hottest and most
oppressive of this stretch, with highs largely in the upper 90s
to near 100, most likely in the I-95 urban corridor. Dew points
remaining in the lower 70s will support peak heat indices of
105-110 degrees across much of the area. Lows Tuesday night will
likely be the warmest of this hot stretch, with lows in the mid
to upper 70s in many areas, and near 80 degrees in the urban
centers. Given the latest forecast is largely unchanged, we have
maintained the current Excessive Heat Warning and Heat
Advisories across the region for Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Summary...Excessive heat Wednesday begins to diminish as a cold
front and associated showers and thunderstorms move toward the
region late Wednesday, then temperatures should be closer to
average Thursday through Sunday with lowered humidity.

Synoptic Overview...An upper-level trough is forecast to pivot
into and across the Northeast and Mid-Atlantic regions Thursday
into Friday. The western Atlantic ridge may try to expand
eastward again into the Mid-Atlantic Saturday, however an upper-
level trough is forecast to remain from eastern Canada down
across the Great Lakes and into the Mid-Mississippi Valley. This
may be enough to keep the main part of the ridge at bay along
with the associated hotter temperatures. At the surface, a cold
front arrives Wednesday night and gradually shifts offshore
during Thursday. High pressure should then extend eastward into
our area Friday into Saturday.

For Wednesday and Thursday...As an upper-level trough arrives,
a cold front will approach during the day Wednesday before
crossing our region Wednesday night and Thursday. A pre-frontal
trough may also develop on the leeward side of the mountains.
This combined with increasing forcing for ascent and greater
effective shear should result in showers and thunderstorms
developing and becoming more widespread with time, especially by
late afternoon and evening. The convective organization may be
more tied to the pre-frontal trough as it shifts eastward later
Wednesday, and given ample instability and enough shear some
thunderstorms could be strong to severe Wednesday afternoon and
evening. The details however remain a bit unclear. The highest
PoPs are included Wednesday afternoon and evening, however the
PoPs remain at least in the chance range Thursday for most of
the region as the front may be slow to clear our area. High
temperatures are forecast to be well into the 90s yet again,
with resulting heat indices near 100-107 or so across much of
the area (especially along and south of I-78). Thus, the
Excessive Heat Watch remains in effect for Wednesday. The
arrival of convection and also the cold front will knock down
the excessive heat, and therefore Thursday is expected to be
noticeably cooler and drier than Wednesday.

For Friday through Sunday...The main part of the upper-level
trough should be lifting up across the Canadian Maritimes later
Friday, however this trough (weaker form) may extend
southwestward across the Great Lakes and into the Mid-
Mississippi Valley. Pending that the front clears our entire
area by Friday and drier air advects in, precipitation chances
then drop off during this time frame. Surface high pressure
centered near the Midwest should then extend eastward with time
and into our area. This should promote a more light northerly
flow, although may result in a sea breeze both days, and
therefore temperatures much closer to average and also lowered
humidity. By the back half of the weekend though, the high may
lift far enough north that chances for showers and thunderstorms
may return.

&&

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

Today...Any patchy fog will dissipate by 13Z. VFR otherwise.
SHRA/TSRA possible after 18Z and could result in brief
restrictions and strong wind gusts should a storm pass over a
given terminal. Terminals that could be affected are
KRDG/KABE/KTTN/KPNE/KPHL. SW winds 5 to 10 kt, becoming 10 to 15
kt with gusts up to 20 kt this afternoon. Moderate confidence.

Tonight...Any lingering SHRA/TSRA will taper off by 03Z or so.
Primarily VFR, but patchy fog possible again late at night that
could result in sub-VFR VSBYs. Light S winds. Moderate
confidence.

Outlook...

Tuesday through Tuesday night...Generally prevailing VFR. A
20-30% chance of showers or thunderstorms, mainly northwest of
I-95.

Wednesday and Thursday...Showers and thunderstorms likely,
especially Wednesday afternoon and evening, likely leading to
sub-VFR conditions at times.

Friday...VFR conditions with no significant weather expected.

&&

.MARINE...
Conditions remain below Small Craft Advisory criteria. A
prevailing SW flow of 10 to 15 kt will persist for today and
tonight with gusts up to 20 kt or so this afternoon. Seas will
average 3 to 4 feet.

Afternoon and evening thunderstorms may result in VSBY
restrictions in heavy rain, wind gusts in excess of 34 kt, and
frequent lightning strikes.

Areas of fog on the waters will also result in VSBY restrictions
today and tonight, especially for waters very close to the
coast.

Outlook...

Tuesday through Tuesday night...The conditions should be below
Small Craft Advisory criteria. Some fog possible at times.

Wednesday and Thursday...A Small Craft Advisory may be needed,
especially Wednesday. Showers and thunderstorms develop
Wednesday afternoon with some continuing into Thursday. Areas of
fog possible.

Friday...Conditions are expected to be below SCA criteria.

Rip Currents...

For Today and Tuesday, south to southwest flow will average 10
to 15 mph. Gusts up to 20 mph are possible during the daytime
hours. Wave heights will average 1 to 3 feet and a 5 to 7
second period. Therefore, there is a MODERATE RISK for the
development of dangerous and life threatening rip currents for
the Jersey Shore in Ocean, Atlantic, and Cape May counties, and
a LOW risk for the Jersey Shore in Monmouth county and Delaware
Beaches.

Late day showers and thunderstorms are possible, mainly for the
Jersey Shore in Monmouth and Ocean counties.

Some areas of fog at times will cause reduced visibility along
the shoreline.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.CLIMATE...
Near record breaking temperatures are forecast from Monday
through Wednesday. Records for our climate sites are listed
below:

Record High Temperatures
                          July 15
Site                  Record/Year
Allentown (ABE)           98/1995
AC Airport (ACY)         100/1995
AC Marina (55N)           99/1995
Georgetown (GED)          96/1993
Mount Pocono (MPO)        92/1954
Philadelphia (PHL)       103/1995
Reading (RDG)             96/1995
Trenton (TTN)            101/1995
Wilmington (ILG)          99/1995 & 1997

Record Warmest Low Temperatures
                          July 15
Site                  Record/Year
Allentown (ABE)           79/1995
AC Airport (ACY)          78/1995
AC Marina (55N)           80/1995
Georgetown (GED)          75/2012 & 2016
Mount Pocono (MPO)        69/2013
Philadelphia (PHL)        81/1995
Reading (RDG)             79/1995
Trenton (TTN)             78/1995
Wilmington (ILG)          78/1995

Record High Temperatures
                          July 16
Site                  Record/Year
Allentown (ABE)          101/1988
AC Airport (ACY)         100/1983
AC Marina (55N)          100/1983
Georgetown (GED)          97/1953 & 1992
Mount Pocono (MPO)        93/1988
Philadelphia (PHL)       102/1988
Reading (RDG)            100/1900
Trenton (TTN)            102/1988
Wilmington (ILG)         100/1983

Record Warmest Temperatures
                          July 16
Site                  Record/Year
Allentown (ABE)           76/1983
AC Airport (ACY)          77/1983
AC Marina (55N)           80/2013
Georgetown (GED)          80/1955
Mount Pocono (MPO)        70/1955
Philadelphia (PHL)        80/2013
Reading (RDG)             78/1955
Trenton (TTN)             78/1983
Wilmington (ILG)          77/2013

Record High Temperatures
                          July 17
Site                  Record/Year
Allentown (ABE)           99/1999
AC Airport (ACY)          99/2012
AC Marina (55N)           95/1937
Georgetown (GED)         100/2019
Mount Pocono (MPO)        91/1999
Philadelphia (PHL)       102/1988
Reading (RDG)            102/1988
Trenton (TTN)            100/1988
Wilmington (ILG)         100/1988

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Excessive Heat Warning until 6 AM EDT Wednesday for PAZ060>062-
     070-071-101>106.
     Excessive Heat Watch from Wednesday morning through Wednesday
     evening for PAZ060>062-070-071-101>106.
     Heat Advisory until 8 PM EDT Tuesday for PAZ054-055.
NJ...Excessive Heat Warning until 6 AM EDT Wednesday for NJZ009-010-
     012-013-015-017>020-027.
     Excessive Heat Watch from Wednesday morning through Wednesday
     evening for NJZ001-007>010-012-013-015>022-027.
     Heat Advisory until 6 AM EDT Wednesday for NJZ001-007-008-014-
     016-021>023.
DE...Excessive Heat Warning until 6 AM EDT Wednesday for DEZ001.
     Excessive Heat Watch from Wednesday morning through Wednesday
     evening for DEZ001>004.
     Heat Advisory until 6 AM EDT Wednesday for DEZ002>004.
MD...Excessive Heat Warning until 6 AM EDT Wednesday for MDZ012-015-
     019-020.
     Excessive Heat Watch from Wednesday morning through Wednesday
     evening for MDZ012-015-019-020.
MARINE...None.

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...AKL/Johnson/MPS
SHORT TERM...AKL/Gorse/Staarmann
LONG TERM...AKL/Gorse/Staarmann
AVIATION...AKL/Johnson/MPS/Staarmann
MARINE...AKL/Hoeflich/Johnson/MPS/Staarmann
CLIMATE...