084
FXUS61 KPHI 030516
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
116 AM EDT Fri May 3 2024

.SYNOPSIS...
A cold front will stall to our south and west on Friday. A
weakening cold front will move into the region Saturday while a
stronger front moves in later Sunday. After a couple of mostly
dry days another front will approach towards midweek.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast running on track, so no significant changes will be
made with this update.

A cold front is moving southward through the region as low
pressure moves southeastward off the coast of New England and
high pressure builds into eastern Canada. This setup will shift
winds to a north to northeast direction into tonight over the
mid Atlantic. This will eventually bring in some marine stratus
and perhaps some fog along the coast late tonight into Friday
morning. The stratus should make it into the I-95 corridor and
Lehigh Valley as well by around daybreak or so. Expect overnight
lows mainly in the 50s...ranging from low 50s over the southern
Poconos, NW NJ, and and the NJ coast to mid/upper 50s near the
urban corridor of SE PA extending south into interior portions
of Delmarva.

For Friday, ridging aloft will keep the area dry for at least
one more day as it helps to keep the approaching system from
the west at bay. Meanwhile the front will be stalled to our
south but then arcing back to the north and west into PA just
west of our region. The upshot of this is it will be a much
cooler day with continuing easterly winds and mostly cloudy
skies. Through the morning, marine stratus across the eastern
half of the area will be slow to mix out into the late morning
and early afternoon with the modest easterly wind near 10-20 mph.
Meanwhile by afternoon there will be some clouds moving in from
the west. So not a completely sunny day but much of the region
should see at least a little sun at some point except perhaps
right along the coast. Speaking of which, expect highs near the
coast will only get into the mid to upper 50s with warmer
temperatures the farther west you go. Eastern PA down to the
eastern MD shore should see highs mainly in the upper 60s to low
70s except some mid 70s over portions of Berks County.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Wedge of Canadian high pressure will continue nosing
southwestward along the coast Friday night through Saturday
night, keeping the frontal boundary which moves through tonight
stalled to our southwest with a cooler maritime air mass in
place over our region. A weakening cold front will be moving
into the area from the west, but it will be too weak to dislodge
the maritime air in place, and the front will wash out. Showers
and thunderstorms associated with said front will develop to
our west, especially Saturday and Saturday night, but are
expected to weaken and eventually die out as they continue
advecting eastward into the stable maritime air mass. Thus, POPS
are highest in the far west/Poconos and much lower along the
coast. Clouds will dominate thanks to the maritime influence and
temps will be in the upper 40s to lower 50s, with highs
Saturday in the upper 50s to 60s.

By Sunday, another, stronger cold front will be approaching from
the west. This one looks likely to bring enough of a
southwesterly push ahead of it to at least partially dislodge
the stalled boundary to our southwest, which may bring 70s back
into the Delmarva. Further north, it looks likely to stay stuck
in the maritime air, with 50s and 60s more likely, along with
continued mostly cloudy conditions. This stronger boundary from
the west, however, looks more likely to spread showers and
perhaps some mostly elevated thunderstorms into the region, so
POPs are much higher on Sunday compared to Saturday. That said,
still not expecting a lot of rain, mostly in the half inch rain,
though locally more could be had with any heavier storms,
especially NW of I-95.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The stronger cold front moving in Sunday will try its best to
dislodge the marine layer for the balance of the week, though
a boundary of some sort will remain nearby through the entire
week. This boundary will continue to form the basic path of
additional waves of low pressure moving eastward across the
northern US. Given uncertainty about exactly where the boundary
ends up each day, which will depend on passing low pressure
waves and high pressures building in behind each one, have kept
temps relatively stable in the 70s for highs and 50s to 60s for
lows. Chance of precip appears to ebb behind the front Monday
and Tuesday, but will return with additional waves of low
pressure Wednesday and Thursday. Still a lot of uncertainty
regarding timing of waves so confidence is not great regarding
details.

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Initially VFR much of the night. Expect some MVFR
cigs after 09Z reaching as far inland as the I-95 corridor and
Lehigh Valley. Less certainty that the MVFR ceilings will reach
ILG and RDG. Any visibility restrictions should be confined to
ACY. Winds near 5-10 knots and shifting to the north to
northeast as a cold front passes the area. Northeast winds then
prevail overnight, shifting more easterly toward 12Z. Moderate
confidence overall.

Friday...MVFR ceilings to start will be slow to scatter out
toward 15-18Z, though there should be improvement to VFR
everywhere by 18Z or so. Winds generally easterly around 10
knots with gusts near 20 knots at ACY. Moderate confidence.

Outlook...

Friday night...MVFR cigs possible esp toward coastal sites.

Saturday...MVFR cigs possible.

Sunday...MVFR conds likely with IFR conds possible.

Monday...VFR likely.

Tuesday...VFR likely.

&&

.MARINE...
Sub-Small Craft Advisory conditions through tonight. Northeast
winds around 10 kt tonight. The main concern late tonight into
Friday morning will again be the potential for marine dense fog.
Have added mention of fog to the forecast. Visibility could
drop lower than 1 NM at times and a Marine Dense Fog Advisory
may need to be considered through Friday morning.

Easterly winds increase to near 15-20 kts on Friday with some
gusts near 25 kts possible. Seas will average 2 to 3 ft through
tonight and then 3 to 4 ft by later Friday. Seas may reach near
5 feet at times. A Small Craft Advisory may be needed, although
confidence in reaching criteria for more than an hour or two is
low.

Outlook...

Friday night through Saturday...No marine headlines
anticipated.

Saturday night through Sunday...SCA conditions possible
(20-30%) as seas near 5 feet on the ocean.

Sunday through Monday...No marine headlines anticipated.

&&

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

&&

$$

SYNOPSIS...Fitzsimmons/RCM
NEAR TERM...Fitzsimmons/MPS/Staarmann
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...Fitzsimmons/MPS/RCM/Staarmann
MARINE...Fitzsimmons/RCM/Staarmann