200
FXUS61 KPHI 030524
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
124 AM EDT Wed Jul 3 2024

.SYNOPSIS...
High pressure moves offshore today. A more active period begins
Thursday with the arrival of a surface trough, bringing hot and
humid conditions along with chances for showers and storms each
day into the weekend. A frontal boundary may linger across the
region into early next week, with generally unsettled conditions
persisting.

&&

.NEAR TERM /THROUGH TONIGHT/...
Surface high pressure is currently centered just to our
northeast over southern New England, and it will slowly slide
eastward through today and tonight as a cold front, currently
over the western Great Lakes, presses southeastward toward us.
Despite this shift in surface pattern, the flow will not bring
the big surge of humidity until tomorrow, so we have one more
day of relatively low humidity, with afternoon dew points likely
to drop back into the 50s again. Aloft, the ridge axis currently
over western PA will shift over us by this afternoon, then off
shore tonight. Some mainly high clouds are passing over the
ridge and will keep today from being perfectly sunny, but
greater cloud cover will not invade until tonight. Today and
most of tonight should also be dry, but as the warm front with
the humidity push moves in late tonight and some dying
convection approaches from the northwest, our northwestern
zones, especially the Poconos, could see a late night shower or
thunderstorm. Highs today will be in the 80s for most, similar
to yesterday, with lows tonight staying a touch milder with the
clouds and humidity starting to build, with 60s common.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
High pressure will continue to move offshore into Independence
Day as a surface low and associated upper level trough move
eastward through eastern Canada. This will push a warm front
through the region early in the day Thursday allowing the area
to get into the warm sector. The warm front could bring a few
isolated showers or storms Thursday morning, mainly over NE PA
into NW NJ, with the greater chances for showers and storms
arriving later in the day Thursday. Prior to this, the other
story for the day will be the return of the heat and humidity as
highs for most areas will reach the upper 80s / low 90s (cooler
near the coast and over the Poconos) with dew points reaching
the upper 60s to low 70s. This will result in max heat indicies
well into the 90s to near 100 for most areas. As for the storm
threat later in the day, expect storms to fire in the vicinity
of a weakening frontal boundary draped over PA by the afternoon
hours with these storms moving eastward into our eastern PA and
northern NJ zones by later in the afternoon and then potentially
affecting Delmarva and southern and coastal NJ by the evening.
So it won`t be an all day type rain event but unfortunately the
timing won`t be great as it could interfere with Independence
Day festivities. Our POPs generally range from around 50 to 60
percent over eastern PA to 40 to 50 percent near the coast. With
ML CAPE values progged to max out around 1000-1500 j/kg along
with deep layer shear values around 30 knots there is the
potential some storms could become severe and it`s worth noting
the SPC has SE PA, Delmarva, and parts of southern NJ in a
MARGINAL risk for severe weather for Thursday. With PWATs
progged to reach 2.25+ inches, storms will also be capable of
producing very heavy rain which could lead to localized
flooding.

Storms may linger into a good portion of the evening Thursday
before diminishing overnight. It will be a very warm and muggy
night as the frontal boundary gets hung up over the area. Most
areas won`t see lows getting below the low/mid 70s (except 60s
over the Pocono).

The front will remain draped over the area Friday as it extends
to a new low developing over the midwestern States that will
lift northward towards the Great Lakes. This will result in
another hot, humid day with chances for afternoon and early
evening storms once again. Storms should be a little less
widespread though compared to Thursday and this is reflected in
our POPs which are more in the 20 to 30 percent range.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Low pressure lifts northward into Ontario Friday night into
Saturday with a strengthening southerly flow developing in the
warm sector over the area ahead of an approaching cold front.
This will ratchet up the mugginess even further with dew points
potentially reaching over 75 by Saturday afternoon. Combined
with forecast highs for Saturday once again in the upper 80s to
low 90s for most areas, this could bring peak heat indices in
the range of 102 to 107 meaning heat headlines would be needed
if this forecast holds. The synoptic scale lift provided by the
cold front along with abundant moisture looks to result in
widespread showers and storms by Saturday afternoon into the
evening. And at this point, both severe weather and flash
flooding look to be a threat. Am particularly concerned seeing
progged PWAT values by both deterministic models and ensembles
in the range of 2.25 to 2.5 inches which is close to
climatological maxes.

Looking beyond Saturday into early next week, the cold front
will move through into Sunday but also tend to stall and "wash
out" as it moves across. Thus, while Sunday into early next week
should be a little more comfortable compared to Saturday in
terms of heat and humidity, it will still be quite warm and
humid. Each day will also see continuing chances for scattered
showers/storms, mainly during the afternoon and early evening
hours, with POPs generally around 30 percent.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Until 12Z this morning...Mainly VFR. However, some patchy fog
development may cause sub-VFR visibilities at KACY toward dawn.
Otherwise, mostly clear skies expected. Winds light and variable
and/or out of the S/SSE at 5 kts or less. High confid overall,
but lower confid in patchy fog development and timing for KACY.

12Z this morning through 0Z this evening...VFR. Ci clouds with
some diurnal Cu possible too. Light S winds becoming 5-10 kts.
High confid.

Tonight...VFR with no significant weather. Winds generally
southerly around 5 kts. High confidence.

Outlook...

Thursday through Sunday...Sub-VFR conditions possible with
chances (30-60%) for SHRA and TSRA, especially in the afternoon
and evenings each day. The best chances for more widespread
showers and storms looks to be Saturday at this point.

&&

.MARINE...
Sub-SCA with mostly fair weather today and tonight, though will
need to watch for any early morning marine fog which could
necessitate a marine dense fog advisory. Light S or SE winds
increasing to 10-15 kts by this afternoon and tonight.

Outlook...

Thursday through Sunday...Conditions are forecast to be below
Small Craft Advisory criteria through the period though
southerly winds may gust to around 20 knots at times. There will
also be daily chances for showers and storms through the
period...especially in the late afternoon and evening periods.

Rip Currents...

Today...Southeast winds around 5-10 mph. Breaking waves remain
around 1-2 feet. Despite more of an onshore flow, with light
conditions expected, have continued with a LOW risk of dangerous
rip currents for both the Jersey Shore and Delaware Beaches.

4th of July...Southerly winds strengthen with breaking wave
heights increasing. With an onshore component to the wind for
Cape May, Atlantic, and Ocean County, there is a MODERATE risk
for rip currents. With wind direction more shore
parallel/offshore at the Delaware Beaches and northern Jersey
Shore, have elected to go with a LOW risk. Breaking wave of 2 to
3 feet, though some 4 foot waves are possible within the
MODERATE risk area.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...AKL/Fitzsimmons/RCM/Staarmann
NEAR TERM...RCM
SHORT TERM...Fitzsimmons
LONG TERM...Fitzsimmons
AVIATION...Fitzsimmons/OHara/RCM/Wunderlin
MARINE...Fitzsimmons/Hoeflich/OHara/RCM/Wunderlin