664
FXUS61 KPHI 250834
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
434 AM EDT Sat May 25 2024

.SYNOPSIS...
A frontal boundary remains over the area today, and then a cold
front approaches from the west tonight and washes out before it
crosses the region. Weak surface high pressure will be over the
area, but several upper level disturbances will impact the area
Sunday night through Monday. A stronger cold front will pass
through the region Monday night. Weak high pressure returns
Tuesday, but weak low pressure passes through on Wednesday. High
pressure closes out the new work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Weak high pressure has brought mostly calm winds and clear
skies across the region early this morning with temperatures
falling into the upper 50s to low 60s (mid 60s in the urban
corridor). With dew points in Delmarva and southeastern New
Jersey in the upper 50s to low 60s as well, the aforementioned
conditions have resulted in the formation of patchy fog across
this portion of the area. In the more dense patches,
visibilities less than 1 mile have been observed. Patchy fog is
expected to continue through the pre-dawn hours then should burn
off relatively quickly after sunrise with mostly clear skies
continuing.

Clouds will begin to increase later this morning and into this
afternoon though as a weak warm front passes through the region.
A shower or two may form in the vicinity of this front, most
likely northwest of the I-95 urban corridor, where forcing will
be a bit greater. Temperatures will be in the mid 80s across the
region except at the immediate shore where mainly low 70s are
expected.

Greater chances for showers or a few thunderstorms will be
later this evening and into the overnight hours tonight.
Decaying convection initiated well west of our area will be
pushing in as a weak trough moves through. CAM guidance is still
relatively split over the extent and strength of the storms by
their arrival into the region but even the more robust solutions
indicate scattered coverage of showers and storms at best.
Maintained chance PoPs (20-40%) as a result with the higher
chances northwest of the I-95 corridor and less than 15% along
the Jersey Shore and Delaware Beaches.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Unsettled weather on tap for the start of the new week. While
most of Sunday will be dry, an upper level trough approaches
from the west, and some shortwave energy will race out towards
the Northeast Sunday afternoon. A warm and humid airmass will be
in place over the area with highs in the low to mid 80s and
surface dew points well in the 60s. Scattered late day and
evening showers and thunderstorms are possible for the southern
Poconos, Lehigh Valley, and northern New Jersey.

Low pressure will continue to organize and develop Sunday night
and will lift into the Great Lakes and eastern Canada Monday
and Monday night. A warm front extending out from that low will
lift north through the region Sunday night, and a more organized
round of convection will develop and lift towards the western
portions of the forecast area late Sunday night through Monday
morning.

A cold front then approaches from the west as low pressure
moves into eastern Canada, and showers and thunderstorms will
develop out ahead of the front and will move into the region
late Monday and Monday night. This will trigger yet another
round of showers and thunderstorms. Given abundant low level
moisture with surface dewpoints well in the 60s and around 70,
PWATs will be up around 2 inches. Thunderstorms will be capable
of heavy rain and localized flash flooding, mainly for eastern
Pennsylvania and northern New Jersey. While severe weather is
possible, instability may be limited by thunderstorms earlier in
the day.

Cold front works its way through the region Monday night.
Showers and thunderstorms taper off after midnight from west to
east and will end by daybreak Tuesday.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
A secondary cold front passes through the region Tuesday
morning as low pressure lifts into eastern Canada, where it will
meander for most of the new week. Although the airmass will not
be appreciably cooler, it will be much less humid as surface
dew points drop from the mid and upper 60s to the mid and upper
50s. An H5 trough with strong shortwave energy will move from
the Great Lakes into the Ohio Valley and western New York and
western Pennsylvania, and a few isolated showers and
thunderstorms may move into the southern Poconos Tuesday
afternoon. Conditions will otherwise be dry and mild.

Low pressure develops over the Mid-Atlantic on Wednesday as
that upper trough builds east, touching off scattered showers
and thunderstorms during the day.

Thereafter, surface high pressure builds in from the north and
west as an upper trough remains over the Northeast. Going into
the end of the week, conditions will be mainly dry, but cannot
rule out an isolated shower or thunderstorm. It will also be
cooler with below normal temperatures.

&&

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

Early this morning...Clear skies and calm winds for I-95/Lehigh
Valley terminals. Patchy fog is causing conditions to drop sub-
VFR at times at coastal terminals. Mainly MVFR conditions
expected with fog reducing vsbys to 3-5 miles but visibilities
less than 3 miles have been observed. Moderate confidence.

Saturday...VFR. Widely scattered showers and thunderstorms late
in the day in the Poconos and Lehigh Valley. Southerly winds
5-10 knots. High confidence in prevailing VFR conditions.

Tonight...A period of sub-VFR conditions with some showers and
a thunderstorm possible (25-35% chance), most likely for I-95
and Lehigh Valley terminals. Southerly winds around 5 knots or
less. Moderate confidence.

Outlook...

Sunday through Wednesday...Overall, VFR on Sunday, and then
SHRA and TSRA will impact the terminals with sub-VFR conditions
starting Sunday night, but primarily Monday and Monday night.
VFR Tuesday and Wednesday, although scattered SHRA/TSRA with
brief sub-VFR conditions possibly Wednesday.

&&

.MARINE...
The conditions are expected to remain below Small Craft
Advisory criteria through tonight with seas of 1-2 feet and
winds of 5-10 knots. Fair weather.

Outlook...

Sunday through Wednesday...Sub-SCA conditions overall, but a
brief period of SCA conditions with 25 kt wind gusts and seas
around 5 feet may occur Monday night through Tuesday morning.
Thunderstorms Monday afternoon and night could result in strong
wind gusts and VSBY restrictions in heavy rain.

Rip Currents...

Both Saturday and Sunday will feature a LOW risk for the
development of rip currents. While there will be a light onshore
flow with south/southeast winds, breaking waves of only 1 to 2
feet and a short period of less than 8 seconds will mitigate the
rip current potential.

As always, rip currents can still develop, and often occur in
the vicinities of jetties and piers. Utilize any guarded beaches
this holiday weekend if venturing out into the water.

&&

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

&&

$$

SYNOPSIS...MPS
NEAR TERM...AKL
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...AKL/MPS
MARINE...AKL/MPS