796
FXUS61 KPHI 180641
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
241 AM EDT Wed Jun 18 2025

.SYNOPSIS...
A slow moving warm front will gradually lift northward across
the region this morning. Bermuda high pressure sets up offshore
today and Thursday. A regime change occurs towards the end of
the week as a cold front passes through the region Thursday
afternoon and night. High pressure should then generally
dominate for the end of the week through the weekend into early
next week with a building ridge aloft over the east coast
through this period.

&&

.NEAR TERM /THROUGH TONIGHT/...
The warm front remains hung up across the region early this
morning, so low clouds, mist and drizzle have returned,
especially along the coast and in the higher terrain. In
addition, a weakening vort max is moving through with dying
t-storms, resulting mostly in just some showers across the
region. A rumble of thunder can`t be completely ruled out
however, especially closer to the warm front in the Delmarva.
Expect these showers to mostly depart by dawn, but the
fog/drizzle/mist will remain.

After sunrise, expect the warm front to make better progress
northward, pushing mostly clear of the region though possibly
getting hung up around the NYC metro area. Thus,
clouds/mist/fog/drizzle should break for some midday sun, and
temps should warm rapidly into the 80s for most, with southern
areas flirting with or slightly passing 90 away from the coast.
With plenty of humidity, heat indices will be notably above air
temps, so have maintained head advisory as inherited for today.
Might flirt with criteria south of the present advisory (where
criteria is higher) as well but confidence not quite there yet.
Certainly it will feel very summery for much of the region by
early this afternoon.

After that it will probably start to sound rather summery as
well as another vort max approaches, and combined with CAPE
values likely to exceed 2000 J/kg plus some modest shear, it
appears that a round of afternoon/early evening thunderstorms
will be a good bet for most of the region. We remain outlooked
for a marginal severe weather risk. Storms should be moving
along, but locally heavy rains will also be possible given
ample moisture.

After the storms dwindle, with the front possibly hung up near
NYC, northeastern areas could see a return of some patchy
fog/mist/drizzle, but unlike tonight, the majority of the region
should just be warm and humid. Lows near or above 70 for most.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
A shortwave axis will be located over the Ohio Valley on
Thursday morning, shifting eastward towards our area by the
evening hours. At the surface, low pressure will be located over
portions of Ontario Thursday morning, tracking eastward into
southern Quebec and far northern portions of New England through
the day. A cold front associated with this surface cyclone will
pass through the area during the late afternoon and evening
hours.

Ahead of the aforementioned cold front, very warm and moist
southwesterly flow will continue across the area. Underneath
partly to mostly sunny skies, strong surface heating is
anticipated, with temperatures generally climbing into the upper
80s to near 90 across eastern PA and northern NJ, and into the
lower 90s near/southeast of the I-95 corridor.

With quite a bit of moisture in place (surface dewpoints in the
lower 70s), it will feel quite hot. Heat indices will climb
into the upper 90s southeast of the Lehigh Valley and away from
the immediate coastal strip. Due to the potentially dangerous
heat impacts, a heat advisory will be in effect for the urban
corridor through 8 PM Thursday.

In addition to the dangerous heat, severe weather remains a
concern Thursday afternoon and evening. Aided by background
ascent from the approaching shortwave, the cold front should
provide a focus for the development of scattered thunderstorms
by mid-afternoon across western portions of our area, tracking
east into the late afternoon and evening hours. The environment
ahead of the cold front is expected to become moderately
unstable (MLCAPE values of 1500-2000 J/kg). Deep layer shear on
the order of 30-35 kt will support primarily multicell clusters
initially, though a supercell or two cannot be ruled out.
Forecast soundings indicate a fairly deep mixed layer, and
strong downdraft winds appear to be the primary threat with this
activity. A few instances of marginally severe hail cannot be
ruled out during the relatively early stages of convective
evolution. With time, storms could have a tendency to grow
upscale due to strong frontal forcing and possible cold pool
development. Should upscale growth occur, the potential would
exist for damaging winds to be somewhat widespread, therefore
this will need to be monitored closely. Similar to today, PWATs
will be in the neighborhood of 2" and forecast soundings indicate
tall CAPE profiles supportive of efficient rainfall production.
While widespread flooding concerns are not anticipated,
localized urban flooding cannot be ruled out with any stronger
storms.

The cold front will clear the area from west to east Thursday
night. Behind the front, skies are expected to clear out with a
cooler and drier northwest wind. Lows Thursday night are
expected to range from near 60 for the Lehigh Valley and
northward to the mid-upper 60s across the Delmarva.

High pressure will begin taking shape across the region on
Friday. Mostly clear skies are anticipated. It will still be
warm, with temperatures generally in the low-mid 80s areawide.
However, it will be much less humid, and thus will feel much
more comfortable.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Significant mid-level ridging will continue to take shape to
our southwest across central and southeastern portions of the US
heading into the weekend, and expanding across our area through
early next week. It is not out of the question that
northwesterly flow on the periphery of this expanding ridge
could have a weak impulse or two provide parts of the area with
low precipitation chances this weekend. Overall, however, high
pressure will become firmly in control. The primary story in the
extended period looks to be very warm temperatures during the
late weekend and into early next week. For next Monday and
Tuesday, highs for much of the region are forecast to be in the
middle to high 90s with heat indices forecast to exceed 100.
The exception will be along the coast and in the Poconos where
it will be a bit cooler.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Thru 12Z...LIFR/IFR for all terminals at times overnight.
Scattered showers expected with intervals of mist/drizzle and
possible fog. Southeast winds will gradually turn more southerly
around 5 kt or less. Low-moderate confidence.

Today...Lingering IFR ceilings in the morning, should
drastically improve to VFR ceilings by the afternoon. Showers
and scattered thunderstorms during the afternoon will be
possible, causing potential sub-VFR ceilings once again. South-
southwest winds around 7-12 kt. Moderate confidence.

Tonight...Showers/storms early should diminish and we may
actually stay VFR for most terminals all night as south-
southwesterly flow remains dominant, though still 5-10 kts.
Moderate confidence.

Outlook...

Thursday through Thursday night...VFR in the morning. Scattered
showers and storms during the afternoon and evening hours could
lead to periods of sub-VFR conditions. Improvement back to VFR
is anticipated overnight Thursday night.

Friday through Sunday...VFR.

&&

.MARINE...
A Marine Dense Fog Advisory is now in effect through noon
Wednesday for all waters due to areas of dense fog with visibilities
1 nautical mile or less. Further extensions may become
warranted based on trends and later observations.

Otherwise, no wind/sea hazards are in effect through tonight.
Intervals of showers, drizzle, mist, and fog early this morning,
with a separate round of showers and thunderstorms for
this afternoon. South-southeast winds around 5-10 kt early this
morning, becoming south-southwest around 10-15 kt later today
into tonight. Seas of 3-4 feet.

Outlook...

Thursday through Thursday night...Conditions may briefly
approach SCA criteria during the afternoon, with southerly wind
of 20-25 kt and wave heights of 4-5 ft. Scattered showers and
storms could also lead to locally rough seas during the
afternoon and evening.


Friday through Sunday...Sub-SCA conditions are anticipated with
winds below 25 kt and seas below 5 ft.

Rip Currents...

For today, winds become south-southwesterly and increase to
10-15 mph. Swell initially begins onshore before also turning to
the south-southwest, becoming more shore parallel with the
swell period remaining around 6-7 seconds throughout. As a
result, breaking waves in the surf zone look to be around 2-3
feet for the central and northern Jersey Shore and 2 feet or
less southwards of there. Therefore, a MODERATE risk for the
development of rip currents is forecast for Jersey Shore beaches
from Atlantic City northwards today with a LOW risk for the
Cape May shore and Delaware Beaches.

For Thursday, winds and swell remain oriented south-
southwesterly. However, winds increase to 15-20 mph with seas
increasing to around 4 feet. As a result, breaking waves in the
surf zone of 2-3 feet look to occur across all beaches.
Therefore, a MODERATE risk for the development of rip currents
is forecast for all beaches on Thursday.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Heat Advisory from 11 AM this morning to 8 PM EDT Thursday for
     PAZ070-071.
     Heat Advisory from 11 AM to 8 PM EDT Thursday for PAZ104-106.
NJ...Heat Advisory from 11 AM this morning to 8 PM EDT Thursday for
     NJZ017>019.
     Heat Advisory from 11 AM to 8 PM EDT Thursday for NJZ015.
DE...Heat Advisory from 11 AM this morning to 8 PM EDT Thursday for
     DEZ001.
MD...None.
MARINE...Dense Fog Advisory until noon EDT today for ANZ430-431-450>455.

&&

$$

SYNOPSIS...Cooper/Deal/RCM
NEAR TERM...RCM
SHORT TERM...Cooper
LONG TERM...Cooper/Fitzsimmons
AVIATION...Cooper/RCM
MARINE...Cooper/RCM