130
FXUS61 KPHI 220745
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
345 AM EDT Wed May 22 2024

.SYNOPSIS...
High pressure moves out to sea today, while a cold front and
pre frontal trough approach the area from the west. The trough
will settle into the area through Thursday, then the cold front
will move across the area Thursday night and stall to our south.
Multiple frontal boundaries and low pressure systems are
expected to affect the Mid Atlantic region over the weekend into
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Some patchy fog near the coast possible this morning, but
otherwise coverage looks rather confined. Any morning fog is
expected to mix out shortly after daybreak.

High pressure offshore will begin to move further out to sea,
losing its grasp of control on the weather across the area. By
the afternoon, a pre-frontal trough will be making its way
across central Pennsylvania late in the day which may spark up a
few showers and thunderstorms. Strong daytime heating will
provide instability and bring afternoon temperatures into the
mid to upper 80s. MUCAPE values will extend around the 1000-1500
J/kg range with rather steep low-level lapse rates. Some
limiting factors, though, will be a lack of deep layer shear in
place and the greatest forcing being displaced well north and
west of the area. This said, we could still see some marginally
severe thunderstorms develop across central PA and shift towards
eastern PA late in the day. These storms would be mainly
isolated to scattered in coverage and have the potential to
bring some gusty winds and small hail. Modest PWAT values around
1.25-1.50" will also support a quick downpour associated with
stronger storms, but flooding concerns remain low at this point.
SPC has outlined a Marginal Risk for severe weather north and
west of the I-95 corridor, mainly encompassing eastern PA and
northwest NJ.

Showers and storms could persist into the overnight period as
well with the prefrontal trough lingering through early Thursday
morning. Storms will lose steam after sunset with the loss of
daytime heating, though an isolated thunderstorm can`t be ruled
out overnight. Lows in the low to mid 60s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
On Thursday, a pre-frontal trough will be in place across the
Mid Atlantic region, while a cold front will be approaching from
the west. A couple of rounds of showers and thunderstorms will
be possible Thursday into Thursday evening. As daytime
instability begins to develop through the day, showers and
thunderstorms could begin to develop as a short wave moves into
the area and interacts with the surface trough. CAPE values
increase to 1000-2000+ J/kg, and shear values will reach 25-35
knots, even though mid-level winds are fairly weak; generally
30-40 knots or less. Some storms could become strong to severe,
with hail or damaging winds possible. While the main threat for
severe storms will be during the day and into the evening hours,
there will remain the potential for showers and thunderstorms
into the overnight hours as the cold front slowly continues to
move across the area. PW values reach 1.25-1.50+ inches, so
there will be periods of heavy rainfall with any showers and
thunderstorms.

The cold front is expected to push to the south of the area
Friday and stall there and likely dissipate, before a backdoor
front may sag southward into the area from the north. PW values
drop through the day Friday into Friday night, but remain
elevated across southern New Jersey, Delaware, and eastern
Maryland, especially early in the day Friday. So these areas
have the best chance of showers Friday into Friday night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Unsettled weather is expected for the weekend into early next
week as multiple frontal boundaries and low pressure systems
will move across or near the area. The weekend does not look
like a wash out, and may be dry for most areas. Any shower
activity will likely be focused around a couple of short
wave/vorticity impulses as any fronts moving into the area over
the weekend look to be fairly weak and only a modest increase in
PW values is expected. One is expected later Saturday into
Saturday evening, and the other later Sunday into Sunday night.

Moving into Monday and Tuesday, precipitation chances will be
higher as a stronger front and is expected to move into the area
while additonal short wave/vorticity impulses move across the
area and an increase in PW values is expected.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Early this morning (through 12Z)...VFR with clear skies. A few
low clouds and patchy fog will be possible at KACY/KMIV,
although not expecting any significant restrictions. South-
southwest winds decreasing to around 5 kt or less. Moderate
confidence.

Wednesday...VFR expected with increasing high clouds during the
afternoon. Slight chance (15%) of a late day thunderstorm at
KRDG/KABE. South-southwest winds around 10-15 kt. High
confidence.

Wednesday night...Sub-VFR conditions possible with a chance for
isolated showers and thunderstorms (30%) overnight, mostly
north and west of KPHL and mainly across KRDG/KABE. Otherwise,
VFR conditions are forecasted, though some patchy fog cannot be
ruled out, especially across locations that see rainfall. Winds
generally light out of the S to SSW. Moderate confidence.

Outlook...

Thursday-Thursday night...Sub-VFR conditions possible with a
chance of showers and thunderstorms.

Friday-Friday night...Mostly VFR conditions expected with a
slight chance of showers during the day.

Saturday-Sunday...Generally VFR conditions are expected, with a
chance of lower conditions with a chance of showers.

&&

.MARINE...
No marine headlines through Wednesday night. Patchy fog
possible over the waters this morning. Otherwise, south-
southwest winds around 10-15 kt with occasional gusts up to 20
kt possible this afternoon and into tonight. Seas around 3-4
feet.

Outlook...

Thursday-Sunday...Conditions expected to remain below Small
Craft Advisory levels. However, winds will gust around 20 knots
at times and seas could rise to 4 feet at times on Thursday.

Rip Currents...

On Wednesday, for the Monmouth County, NJ beaches and the
Delaware Beaches, there is a LOW risk for rip currents as wind
direction will be more shore- parallel with only 2 to 3 foot
breaking waves and an 8 second period. A more onshore component
of the wind will exist for Ocean/Atlantic/Cape May beaches,
where a MODERATE risk for the development of rip currents
remains.

For Thursday, the wind direction goes more southwesterly
(offshore). Breaking waves will only be around 2 feet with a 6
to 8 second period. All beaches will have a LOW risk for the
development of rip currents.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides will be elevated this week with a Full Moon
on Thursday, May 23. Spotty minor coastal flooding will be
possible, especially for the back bays, around the times of the
evening high tide cycle, which will be the higher of the two
tide cycles, going into the end of this week.

&&

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

&&

$$

SYNOPSIS...Robertson
NEAR TERM...MJL
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...MJL/Robertson
MARINE...MJL/Robertson
TIDES/COASTAL FLOODING...