682
FXUS61 KPHI 222021
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
421 PM EDT Sat Jun 22 2024

.SYNOPSIS...
Bermuda high pressure remains in place through Sunday. A cold front
comes through later Sunday, moving offshore by Monday morning. High
pressure settles in for the early part of the week before another
cold front moves in for the middle of the week. High pressure returns
for the end of next week.

&&

.NEAR TERM /THROUGH SUNDAY/...
Hot and humid conditions continue across the CWA this afternoon with
temperatures well into the 90s and dew points in the upper 60s/low
70s most areas. Heat index values are in the upper 90s/low 100s
most spots at the peak heating part of the day. Since we are at
or approaching the Heat Index values needed for an Excessive Heat
Warning in the urban areas, we have started `tomorrows` warning
with the afternoon package and will run it overnight and into Sunday.

Scattered showers/tstms have developed across the region with
the high CAPE conditions and limited shear in place. While most
storms will remain sub-severe, it`s possible that a few may
reach the low-end severe criteria at times. Gusty winds and
localized flooding possible with tstms. The activity will continue
into the early evening before diminishing. After this another
hot afternoon, we can expect another uncomfortable night to follow.
Temperatures will only cool off into the low to mid 70s with upper
70s across the urban corridor and Delmarva. Meanwhile, dew points
will remain in the 70s as well, keeping it mild and muggy tonight.
Lingering showers and storms into tonight may bring some brief
relief temperature-wise, but won`t do anything to reduce the
humidity.

Oppressively hot and humid conditions remain for Sunday, the hottest
day of this stretch of heat. Excessive Heat Warnings were posted
earlier for the urban corridor and parts of the NJ Coastal Plain
as heat indices of 105-110 are expected. We didn`t make many changes
to Sundays temps/dew points with the ongoing fcst on- track.
These conditions combined with the nearly week long stretch of
heat, are going to result in dangerous conditions outside for
Sunday as the effects of heat stress on the body can be cumulative.
Time outside should be limited and if you are out and about,
drink plenty of water!

With such a hot and humid airmass in place, and an approaching cold
front, there will be the chance for some severe weather. Lift will
be aided with a shortwave and pre-frontal trough coming into a moist
and unstable airmass. Deep layer shear of around 30-40kt and moderate
instability (around 1000-2000 J/kg of SBCAPE) will support the development
of thunderstorms capable of producing damaging wind gusts. The SPC
has updated the Day2 outlook to place much of our CWA in a Slight
risk (N/W) and Marginal risk for the shore and most of our Delmarva
area. The limiting factor is the better shear will be located further
north but still think there is sufficient shear to support some strong
to severe thunderstorms. Not overly concerned with the flooding potential
at the moment as storm motion should be steady, though with PWATs
pushing 2 inches, any thunderstorms will produce heavy rain capable
of dropping an inch or two of rain quickly.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
The cold front comes through on Sunday Night/Monday morning, knocking
down dew points a good 15 degrees or so. It will feel much more
comfortable on Monday with dew points back into the 50s and temperatures
getting into the mid to upper 80s. Monday looks unsettled though
as a series of shortwaves rotate around the base of the trough
passing by to the north. This will result in a some scattered
showers and thunderstorms, though the severe potential looks much
lower compared to Sunday. Any showers/thunderstorms will dissipate
after sunset, and it should be a quiet night overall as high pressure
moves in. Temperatures on Monday Night will get down into the 60s.
Tuesday is expected to be dry and hot as a short wave ridge traverses
the region. Temperatures are forecast to climb back into the 90s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Overview: Above normal temperatures will continue for the long-
term, however most of the week with the exception of Wednesday
will not be as oppressive as the heat this weekend.

High temperatures through most of the extended look to be in
the upper 80s/low 90s. The exception being Wednesday, as high
pressure moves offshore resulting in a southerly flow and warm
air advection. For much of the region, this will lead to
widespread 90s (with the exception of the higher terrain in the
Poconos and NW NJ and the immediate coast). May need a Heat
Advisory for some areas (especially the urban corridor), but
want to get through the current heat event before moving on to
Wednesday.

The main rain chances are Wednesday into Thursday as a cold
front approaches and again late in the week (at this point looks
like Saturday or later) as another cold front starts to approach.
Unlike the Sunday event, flooding looks like it could be more of
a concern with the Wednesday system as the front looks to be a
little on the slower side, and we will have a very warm and
moist airmass in place. With such a warm and moist airmass in
place, cannot rule out some stronger thunderstorms as well
especially a downburst/strong wind potential.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

thru the evening...Mostly VFR but scattered showers/tstms with
lower CIGS/VSBYS possible. Mostly KPNE/KTTN/KABE.

Tonight... VFR overall. Few areas of fog possible where rains
occurred today. Medium confid.

Sunday... VFR into the early afternoon then scattered/numerous
showers/tstms moving in from NW to SE during the late afternoon/evening.
MVFR or short periods of IFR possible in tstms. Medium confid.

Outlook...

Sunday night...Restrictions likely with showers and thunderstorms
(60-80%).

Monday...Mainly VFR. Restrictions possible with a chance of
showers/thunderstorms (30-40%) the first half of the day.

Monday night...VFR conditions expected.

Tuesday...VFR conditions expected.

Wednesday into Thursday...Sub-VFR conditions possible (40-50%)
in the afternoon and overnight with showers and thunderstorms.

&&

.MARINE...
No headlines expected through tonight. South winds have increased
to around 15 knots along the shore areas with some gusts in the
low 20s knots at times. Overall, conditions will remain below advisory
criteria. Seas remain 3-4 feet, but begin to build into early Sunday
morning. For Sunday, a SCA will be raised at 8 AM as winds and
seas will build to the low-end of SCA criteria. Scattered
showers/tstms develop late during the day and continue
overnight.

Outlook...

Sunday night...SCA conditions are expected on the ocean waters. S to
SW winds gusting up to 25 to 30 kts. Seas 4 to 7 ft. Showers and
thunderstorms likely.

Monday...Winds are expected to relax, but a residual swell will
remain. SCA conditions are possible. W winds 10 to 15 kts with gusts
up to 20 kts. Seas 4 to 5 ft. A chance of showers and thunderstorms.

Monday night...NW winds 5 to 10 kts. Seas 3 to 4 ft.

Tuesday...W winds 5 to 10 kts, becoming S in the afternoon. Seas 2
to 3 ft.

Wednesday...No marine headlines expected.

Wednesday night into Thursday...Wave heights may get close to 5
feet and gusts close to 25 kt on the Atlantic Coastal Waters.

Rip Currents...

Sunday...With south winds 15 to 25 mph, breaking waves in the 3
to 5 foot range, and a 5 to 7 second wave period, we are
running with a HIGH risk for the development of rip currents for
Cape May/Atlantic/Ocean County and a MODERATE risk for Monmouth
and Sussex, DE beaches. Low tide is mainly in the mid
afternoon.

Monday...Winds relax a bit and back offshore, but wave periods
are forecast to increase. This said, with west winds 10 to 15
mph (maybe some gusts up to 20 mph across the northern beaches),
breaking waves in the 2 to 4 feet range, and a 6 to 8 second
wave period, we are running with a HIGH risk for the
development of rip currents everywhere. Low tide is mainly in
the mid to late afternoon.

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

&&

.CLIMATE...
Record high temperatures today. Sites within the I-95 corridor
and Lehigh Valley have a chance to break their record high temperature.


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...Excessive Heat Warning until 8 PM EDT Sunday for PAZ070-071-
     102-104-106.
     Heat Advisory until 8 PM EDT Sunday for PAZ054-055-060>062-101-
     103-105.
NJ...Excessive Heat Warning until 8 PM EDT Sunday for NJZ010-012-
     013-015>020-027.
     Heat Advisory from 6 AM to 8 PM EDT Sunday for NJZ014-021>026.
     Heat Advisory until 8 PM EDT Sunday for NJZ001-007>009.
DE...Excessive Heat Warning until 8 PM EDT Sunday for DEZ001.
     Heat Advisory from 6 AM to 8 PM EDT Sunday for DEZ002>004.
MD...Heat Advisory from 6 AM to 8 PM EDT Sunday for MDZ012-015-019-
     020.
MARINE...Small Craft Advisory from 8 AM Sunday to 6 PM EDT Monday for
     ANZ450>455.

&&

$$

SYNOPSIS...Hoeflich/Johnson
NEAR TERM...OHara
SHORT TERM...Hoeflich/Kruzdlo
LONG TERM...Hoeflich/Johnson
AVIATION...Hoeflich/Johnson/MJL/OHara
MARINE...Hoeflich/Johnson/MJL/OHara
CLIMATE...Staff