195
FXUS61 KPHI 061407
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1007 AM EDT Mon May 6 2024

.SYNOPSIS...
High pressure remains centered over the Canadian Maritimes and
will sag out to sea throughout the day. Meanwhile, a cold front
approaches from the west and works its way through the region
tonight before becoming nearly stationary south of Delmarva. Low
pressure tracks along the front late tonight through Tuesday
morning. Another area of low pressure passes through the region
on Wednesday followed by a stronger low on Thursday. A cold
front passes through on Friday. Several disturbances are
possible this upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
The Dense Fog Advisory was allowed to expire at 10 am.

For today, a cold front approaches from the west. Warm
advection will ramp up a little bit, though with mostly cloudy
skies persisting, not convinced it will get as warm as the NBM
is showing. Blended in some of the 25th percentile to get todays
high temperatures, with upper 60s/low 70s north and west of
Philadelphia with mid to upper 70s within Delmarva, southern New
Jersey and around the Philadelphia metro. A few showers are
possible ahead of the front as it slowly approaches through the
day. A rumble of thunder can`t be ruled out, though not
expecting any severe weather.

For tonight, the front slowly slides south and east. Forcing
will be enhanced by an incoming shortwave. With the front
positioned over Delmarva/southern New Jersey tonight, periods of
rain and embedded thunderstorms are expected. Most of the rain
should be confined to areas south of Philadelphia, but can`t
rule out a few showers tonight as far north as the I-78
corridor. Again, should just be some garden variety
showers/storms if anything, though anywhere from a quarter to a
half inch of rain is anticipated down around southern New Jersey
and Delmarva. Elsewhere, it will be mostly cloudy with some
patchy fog. Lows will be in the mid to upper 50s/low 60s.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Low pressure will be just east of Delaware and the southern tip
of New Jersey Tuesday morning. Surface dew points across
Delmarva and southern New Jersey will be in the low to mid 60s,
and right after sunrise, SB CAPE values will rise to as high as
500 J/kg. This should be enough for some thunderstorms to flare
up along with those lingering showers. This first round of
showers and thunderstorms should taper off by lunchtime as low
pressure moves offshore. Highs will be around 10 degrees above
normal for this time of the year, topping off in the upper 70s
to around 80 for most of the region, and in the upper 60s to low
70s near the coasts.

Another area of low pressure will track from the Great Lakes
into the Ohio Valley. A warm front extending out from that
system will lift towards southwest portions of the forecast area
late Tuesday and Tuesday night. Scattered showers and
thunderstorms will develop in the afternoon and evening, and
then become likely for most of the region after midnight Tuesday
night and into Wednesday morning as that warm front lifts
through the region. Precipitation tapers off by midday
Wednesday, and then a warm and humid airmass will be in place.
Highs top off in the mid to upper 80s, except for the low 80s in
the southern Poconos and northern New Jersey, and in the 70s
along the coasts. Surface dew points will be in the upper 50s to
low 60s in the afternoon.

Low pressure approaches from the west Wednesday night, and
scattered showers and isolated thunderstorms will move into
portions of southeast Pennsylvania and Delmarva late Wednesday
night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
A closed upper low will move into the Great Lakes, and surface
low pressure develops over the Ohio Valley and tracks towards
western New York and western Pennsylvania on Thursday.
Meanwhile, a secondary low will develop out ahead of this
primary low, and more widespread showers with scattered
thunderstorms will move into the region Thursday afternoon and
evening. Showers and thunderstorms taper off Thursday night as
the secondary low moves offshore. The primary low will track
across northern New York and northern New England on Friday, and
this will drag a cold front through the region Friday afternoon
and evening. Yet another round of scattered showers and
isolated thunderstorms will affect the area during that time.

Behind the cold front, surface high pressure builds east.
Several weak disturbances may touch off some afternoon showers
on Saturday and Sunday.

Clouds and showers will knock temperatures down on Thursday
compared to Wednesday with highs ranging from the low to mid 60s
in the southern Poconos and northern New Jersey to the upper
60s to low 70s for most of southeast Pennsylvania and the rest
of New Jersey to the mid and upper 70s in Delmarva. Highs will
then be in the 60s for southeast Pennsylvania and New Jersey and
in the low to mid 70s in Delmarva on Friday. Below normal highs
expected for Saturday and Sunday, generally in the low to mid
60s.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Low ceilings and patchy fog should lift by 15z-16z or
so. Some sites could lift all the way to VFR. Thinking the
highest chance for that will be within the Lehigh Valley and
I-95 corridor. Otherwise, MVFR CIGs for most of the day once
the fog/low stratus lifts with VFR VSBYs for the afternoon and
early evening. Winds 5 kt or less out of varying directions.
Moderate confidence in timing and extent of restrictions.

Tonight...MVFR/VFR conditions likely drop to IFR around
midnight or so. Some patchy fog possible. Winds light and
variable. Low confidence in timing/extent of restrictions.

Outlook...

Tuesday through Friday...Sub-VFR conditions at night in fog and
stratus, while VFR conditions overall during the day. Chances
for SHRA/TSRA throughout the period with sub-VFR conditions.
More widespread SHRA with scattered TSRA Thursday afternoon and
evening.

&&

.MARINE...
Outside of a Dense Fog Advisory running through 2 pm, there are
no other marine headlines. Seas will be 2 to 4 feet with winds
out of the southeast/south around 5 kts across northern NJ and
5 to 15 kts across our southern waters. Periods of showers
expected, with a 15-20% chance of thunderstorms early Tuesday
morning.

Outlook...

Tuesday through Friday...Overall, sub-SCA conditions through
the period. Scattered showers and thunderstorms will result in
locally higher wind gusts and seas, with biggest impacts coming
on Thursday afternoon and evening.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be elevated this week with a new moon
on Tuesday. Minor tidal flooding and spotty moderate tidal
flooding is likely during the high tide cycles starting Tuesday
evening and continuing into at least Thursday. Coastal Flood
Advisories will be needed.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Dense Fog Advisory until 2 PM EDT this afternoon for ANZ450-
     451.

&&

$$

SYNOPSIS...MPS
NEAR TERM...Hoeflich/Kruzdlo
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...Hoeflich/MPS
MARINE...Hoeflich/Kruzdlo/MPS
TIDES/COASTAL FLOODING...PHI Staff