455
FXUS61 KPHI 232152
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
552 PM EDT Sun Jun 23 2024

.SYNOPSIS...
A cold front will move across the east coast tonight, then
offshore and out to sea on Monday. High pressure will build to
the south the region through Tuesday. Another cold front is
expected to move across the east coast Wednesday night and
offshore by Thursday morning. High pressure builds across the
Mid Atlantic and northeastern states Friday, then offshore
Friday night. Another cold front is expected later Saturday into
Sunday.

&&

.NEAR TERM /THROUGH MONDAY/...
Severe Thunderstorm Watch #449 has been expanded to include the
remainder of the New Jersey counties in our CWA, in addition to
the eastern Pennsylvania and northern New Jersey it already
covered. Models guidance continues to show the cluster of storms
moving across the Philadelphia metro area expanding and
strengthening as it moves eastward, along with other shower and
thunderstorms increasing in coverage and intensity over the
next few hours due to widespread instability and shear across
the area. Damaging winds, hail, heavy rainfall, and frequent
lightning will be possible with any storms. Pay attention to the
skies and keep a source of weather informations handy into the
evening. Tonight, the cold front crosses the area setting off
showers and tstms mostly for the evening hours. The CAPE and
shear conditions remain favorable for tstms which may become
severe at times. The SPC continues with a SLIGHT risk for severe
weather into the overnight. Once the front passes, the
showers/tstms end from NW to SE.

In the meantime, extreme heat and humidity continue over the
area with the Excessive Heat Warning and Heat Advisory flags
continuing. Heat index values in the 100 to 110 range are being
observed as of 2 PM. Once tstms develop, damaging winds and
localized excessive rains are possible.

 Lows will remain very warm with upper 60s N/W and low/mid 70s
S/E. The cooler/drier air will arrive well behind the front.
Winds turn from Southwest to West overnight.

For Monday, the front will be east of the area Monday morning.
Drier and cooler air arrives behind it. Any early morning
showers across ern Delaware or extreme SE NJ around dawn will
end by mid-morning. Clouds will decrease from NW to SE across
the area. Daytime temperatures will be quite a bit cooler for
most areas with mid/upper 70s for the Southern Poconos and
Lehigh Valley areas and low/mid 80s for metro Philadelphia and
much of NJ. A few upper 80s for Delmarva are possible. The dew
points will be much lower with a more comfortable feel to the
air. Winds will be West to Northwest and increase to 10 to 15
mph with gusts to 25 mph at times.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
The short term forecast begins with dry weather expected for
Monday night through Tuesday night. High pressure will build out
of the Ohio River Valley Monday night, across Virginia and
North Carolina during the day Tuesday, then offshore Tuesday
night. Our area will be on the northern fringe of the high, and
even though there area a couple of short wave/vorticity impulses
expected in the northwest to west flow aloft Monday night and
Tuesday, low PW values will not be conducive to precipitation.
By Tuesday night, moisture will be increasing across the area,
but there is not expected to be any forcing mechanism to help
create showers.

As we move into Wednesday and Wednesday night, a cold front
will approach the area from the west late in the day, then move
across the Mid Atlantic region Wednesday night. Wednesday will
likely be another hot and humid day ahead of the approaching
front, similar to this past week and weekend. But thankfully it
looks like the heat should not last long. There will be
instability across the area with CAPE values 500-1000 J/kg,
along with some enhanced shear with values reaching 30-40 knots.
So there will be the potential for some stronger storms to
develop. The cold front will move through overnight, so there
may be a greater chance of showers and thunderstorms overnight,
although the storms may not be as strong during the overnight
hours.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
The aforementioned cold front will move offshore by Thursday
morning and out to sea during the day. There could be some
lingering showers near the coast as the front departs the area,
but most areas will be dry. High pressure will then build across
the Mid Atlantic and northeastern states Friday, then offshore
Friday night. This will bring another period of dry weather to
the area.

Yet another cold front is expected to move across the area next
weekend, although there are some timing differences with the
models. While the GFS and Canadian have the front moving through
as early as Saturday night, the ECMWF has the front moving
through during the day Sunday. So we will keep the higher chance
of precipitation for the Saturday night through Sunday night
period, although it will not likely rain the whole time.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

.Thru the evening... Increasing chances and coverage for
showers and tstms. Lower CIGS/VSBYS included in TAFS for most
likely timing of the tstms. Low confid in which terminals will
be affected and timing is Moderate confid. S/SW winds 10 to 20
kts with G20-25 kts expected, higher gusts in and around
thunderstorms. Medium confid overall.

.Tonight... Showers/tstms moving E thru the area overnight then
ending. Clouds decreasing from NW/SE overnight. CIGS returning
to VFR after showers/tstms end.

.Monday... Any lingering low clouds during the early morning,
most likely near KACY/KMIV, will move away around 12Z. VFR
expected for the day with gusty W/NW winds developing. Gusts of
20 to 25 kts expected. Medium confid.

Outlook...

Monday night...VFR conditions expected. Gusty northwest winds
20-25 knots early in the evening, then northwest 5-10 knots.

Tuesday...VFR conditions expected. Gusty northwest winds around 15
knots during the day.

Tuesday night...VFR conditions expected.

Wednesday...Mostly VFR conditions expected. Chance of showers and
thunderstorms in the afternoon which may lead to lower conditions.
Gusty southwest winds 15-20 knots.

Wednesday night...Periods of sub-VFR conditions possible with
showers and thunderstorms likely.

Thursday...VFR conditions expected. Gusty northwest winds 15-20
knots.

Thursday night...VFR conditions expected

Friday...VFR conditions expected.

&&

.MARINE...
The SCA flag will continue tonight and into Monday for the ocean
waters. The lower Delaware Bay was added too with more gusts and
choppy seas expected to develop this afternoon/evening associated
with showers/tstms. Once the front passes overnight, surface winds
will switch around to W/NW and continue to be gusty into Monday.
Showers/tstms expected to develop later this afternoon and continue
into the early overnight. Fair weather for Monday.

Outlook...

Monday night-Tuesday night...Conditions expected to remain below
advisory levels.

Wednesday-Wednesday night...Conditions may reach Small Craft
Advisory levels.

Thursday-Friday...Conditions expected to remain below advisory
levels.

Rip Currents...

Monday...West-northwest winds around 10-15 mph with gusts up to
20 mph and breaking waves around 2 to 3 feet. Although wind
direction will be directed offshore, wave periods are expected
to increase to around 7 to 8 seconds. For this reason, have
maintained a MODERATE Risk for the development of dangerous rip
currents for both NJ/DE beaches.

Tuesday...Northwest winds will back to southerly as the day
goes on around 10 mph. Breaking waves around 1 to 2 feet. With
winds mainly directed offshore or parallel to the coast and
much lower wave heights, have opted to go with a LOW Risk of rip
currents for all beaches.

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

&&

.CLIMATE...
Record high temperatures for today.

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 this evening for PAZ070-
     071-102-104-106.
     Heat Advisory until 8 PM EDT this evening for PAZ054-055-
     060>062-101-103-105.
NJ...Excessive Heat Warning until 8 PM EDT this evening for NJZ009-
     010-012-013-015>020-027.
     Heat Advisory until 8 PM EDT this evening for NJZ001-007-008-
     014-021>026.
     High Risk for Rip Currents until 8 PM EDT this evening for
     NJZ024>026.
DE...Excessive Heat Warning until 8 PM EDT this evening for DEZ001.
     Heat Advisory until 8 PM EDT this evening for DEZ002>004.
MD...Heat Advisory until 8 PM EDT this evening for MDZ012-015-019-
     020.
MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ431-450>455.

&&

$$

SYNOPSIS...Robertson
NEAR TERM...OHara
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...OHara/Robertson
MARINE...DeSilva/OHara/Robertson
CLIMATE...