353
FXUS61 KPHI 122142
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
542 PM EDT Mon May 12 2025

.SYNOPSIS...
High pressure will be moving out tonight. An area of low
pressure enters the region for the middle of the week and
brings unsettled weather to the area. A series of cold fronts
move through on Friday and Saturday, keeping wet weather in the
forecast.

&&

.NEAR TERM /THROUGH TUESDAY/...
Great weather for the evening and into the early overnight with
increasing clouds and mild temperatures. Temps largely in the
70s this evening will fall back into the 60s overnight most
spots with some mid/upper 50s for lows across the far north.
Clouds will thicken after midnight from South to North as low
pressure begins to inch towards the region. We`ve continued with
a chance for showers around dawn for the West and Southwest
regions with a jump to likely pops shortly after that. There is
still a bit of uncertainty with regards to when the steady rains
begin. Patchy fog will develop too especially near shore areas.
Light South tO Southeast winds overnight.

Tuesday, will continue to see an onshore flow continue for our
area as low pressure moves across the Carolinas. Rains and a
small chance for a tstm are expected for much of the day. The
best chance for thunder will be across Chester and Berks
counties with somewhat more unstable air arriving (aloft) there.
Temperatures Tuesday will remain below normal with all the
clouds and rain, only reaching the upper 60s or low 70s most
spots. Rainfall totals thru the day will range from less than a
tenth of an inch for the NE areas to around a half inch for
metro Philadelphia and Delmarva.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Closed upper lever low centered over Kentucky Tuesday evening
will move north into Ohio by Wednesday morning, gradually
opening up into a shortwave trough as it heads towards Detroit
by Wednesday evening. The remnant low heads towards Toronto by
Thursday morning and on towards Montreal by Thursday evening.
Its during the day Thursday when the upper trough axis crosses
our region, ending up just northeast of us by Thursday evening.
At the surface, a slow moving, weak and diffuse low pressure
will gradually head northeastward from the Carolinas Tuesday
evening to our vicinity Wednesday night, pushing northeast of us
Thursday. This weak low will be accompanied by a warm front,
which means that while Wednesday will be on the cool, cloudy
side, Thursday should see a bit more sun, more instability, and
a better chance for a few thunderstorms. Overall, Tuesday night
through Wednesday looks pretty wet, with plenty of showers, but
meager instability. Thursday will be drier, but spotty
thunderstorms will be a bit more of a risk, mainly inland away
from the marine influence, but with less rain on average. Lows
both nights will be 50s north, 60s south. Highs Wednesday will
be 60s north and east of Philly, 70s south and west, while highs
Thursday will be 70s except along the shore and in the Poconos
where upper 60s remain, while it may touch 80 in parts of the
Delmarva.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Weak ridge builds in Thursday night, with finally a mostly dry
period for the first time since today. Lows will be in the mild
60s for most.

Cold front approaches from the west Friday afternoon, so while a
mostly dry morning is likely, chance of showers and
thunderstorms increases in the afternoon. Could be a severe
weather risk, but still a ways off. Highs up near 80.

Front passes east during Friday night, with waning precip risk.
Not much of a colder push with this front, so lows again mostly
60s.

A second cold front then approaches for Saturday afternoon,
with another mostly dry morning followed by a stormier
afternoon. Highs again mostly near 80.

That front passes east Saturday night, with again a waining
precip risk. Another front with minimal cold push, so lows again
mostly in the 60s.

A third cold front then moves through by late Sunday, with less
moisture to work with but more of a cold air push. Thus, while
highs will again be near 80, chance of precip doesn`t increase
all that much during the day and tanks at night, with lows
dropping into the 50s for most. Highs on Monday then stay mostly
in the 70s.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight... VFR expected into the early overnight with
increasing high clouds. A few showers with lower CIGS may arrive
across Delmarva or perhaps into SE PA after midnight and these
could spread N/NE into srn NJ towards dawn. Light S to SE winds.
High confid early then lowering as the timing of low conditions
not certain.

Tuesday... MVFR conditions with possible high-end IFR looks to
prevail across the area Tuesday. The time when conditions lower
is not certain, but looks to be rather early. Widespread showers
with a small possibility of a late morning or afternoon tstm.
There are better chances for tstms at KRDG and KABE. Southeast
winds mostly around 10 knots. Medium confid overall.

Outlook...
Sub-VFR with intervals of IFR likely through Thursday with
showers and a few thunderstorms. Conditions should improve a bit
Friday and Saturday with less chance of showers, but still a
chance of thunderstorms.

&&

.MARINE...
Fair weather and sub-SCA conditions on the waters this evening
and much of the overnight. Showers and fog will arrive towards
dawn for the offshore Delaware and south NJ waters. On Tuesday,
the rains will spread to the north and envelop all the waters.
Onshore winds will increase thru the day and seas will build as
well.

Outlook...
Small Craft Advisory conditions develop across most water
Tuesday evening and spread to all waters after midnight, with
gusts up to 30 kts and ocean waves up to 7 feet. Southern waters
and the bay will see conditions begin to relax after dawn
Wednesday, but central and northern waters won`t peak until
Wednesday morning, then relax Wednesday afternoon. Winds likely
drop below SCA levels by late Wednesday afternoon, but SCA waves
thresholds of 5 feet may persist on the ocean waters until
during the day on Thursday. Showers and spotty thunderstorms
will also be a concern on the waters through this entire period.

Sub-SCA conditions should then take hold by Thursday evening and
continue through Saturday. However, showers and spotty
thunderstorms may continue to be a risk through Saturday,
especially during the afternoon and evening hours.

&&

.TIDES/COASTAL FLOODING...
Prolonged southeasterly flow will lead to an increase in surge
values as the week progresses, especially for the upper
Delaware Bay and tidal Delaware River. Surge values are forecast
to peak as much as 1-2 feet above normal. As a result, minor
coastal flooding is forecast with the overnight high tide cycles
beginning Tuesday night and continuing through at least
Wednesday or Thursday night.

A Coastal Flood Advisory was issued to highlight the threat of
minor coastal flooding for these areas. Additional advisories or
extensions may be needed in future updates.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory from 1 AM to 6 AM EDT Wednesday for
     PAZ070-071-106.
NJ...Coastal Flood Advisory from 10 PM Tuesday to 2 AM EDT
     Wednesday for NJZ016.
     Coastal Flood Advisory from 1 AM to 6 AM EDT Wednesday for
     NJZ017>019.
DE...Coastal Flood Advisory from 10 PM Tuesday to 2 AM EDT
     Wednesday for DEZ001.
MD...None.
MARINE...Small Craft Advisory from 5 PM Tuesday to 8 AM EDT Wednesday
     for ANZ430-431-451>455.
     Small Craft Advisory from midnight Tuesday night to 8 AM EDT
     Wednesday for ANZ450.

&&

$$

SYNOPSIS...OHara/RCM
NEAR TERM...OHara
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...OHara/RCM
MARINE...OHara/RCM
TIDES/COASTAL FLOODING...Cooper/Staarmann