750
FXUS61 KPHI 160552
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
152 AM EDT Thu May 16 2024

.SYNOPSIS...
An area of low pressure will remain offshore of the Mid Atlantic
coast through Friday, before drifting out to sea. High pressure
tries to build down into the area from the northeast over the
weekend, but never fully makes it into the area before another area
of low pressure moves across the central Appalachians and offshore
of the North Carolina coast later Sunday into Sunday night. Weak
high pressure may finally build across the area early next week,
before a cold front moves across the east coast by mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
We`ll have more of the same today and tonight as the coastal low
remains just east of the region, and will stay there especially
through the day today. It should eventually start to very slowly
drift northeastward away from our region late tonight.

While there will likely be some additional light rain or drizzle
along eastern portions of the coastal plains, for most of the
region, the main impacts will be continued cloudy and
(relatively) cool conditions. Highs today will be mostly in the
60s, except in Berks, Lehigh Valley, and western portions of
Delmarva, where a few breaks in the clouds during the day may
allow for enough solar insolation to result in some lower 70s.

Later tonight, the primary concern is fog potential. Mid level
short wave ridging builds in over the region. This subsidence
coming during the overnight hours could result in a nearly
saturated boundary layer. There remains some uncertainty though
if it will be more of a low stratus or fog event - that will
likely be dependent on if we see any breaks in the persistent
low/mid level clouds during the evening hours.

&&

.SHORT TERM /FRIDAY/...
Low pressure pinwheeling offshore finally moves out to sea
Friday night. The forecast dries out for Friday as high
pressure tries to begin nosing down into the area from the
northeast. Most of Friday night should remain dry as well,
except possibly late in the overnight showers may begin to move
in from the west.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Unsettled weather can be expected for portions of the area this
weekend, especially for the southern third of the area from
southern New Jersey, Delaware, and eastern Maryland. As an area
of low pressure will move across the central Appalachians, then
offshore of the North Carolina coast Saturday into Sunday, a
warm front will lift northward, but remain south of the area.
However, there will be enough moisture and lift across the area
for periods of showers to develop across the southern areas.
High pressure tries to build down from the north, but never
fully sets in, but it may have enough effect on the area to keep
the weather mostly dry for the northern portions area; however,
there will remain a chance of showers even for northern areas
given the proximity of the low and front to the south.

By early next week, the low pressure to the south will begin to
drift out to sea, while high pressure briefly affects the Mid
Atlantic region. Dry weather is expected Monday into Tuesday. As we
move into next Wednesday, a cold front is forecast to move into the
eastern seaboard, bringing an increase in shower chances.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Through 12Z...In general, expect the higher conditions (MVFR to
VFR) to be at KRDG, KILG, KPNE and KPHL, with the lowest (mostly IFR)
persisting at KACY. KABE, and KTTN will likely be hovering
around MVFR for much of the period. The determining factor will
likely be ceiling heights, except at KACY where there has been
transient fog reported. As there are breaks in the lower
clouds, could see highly variable conditions at some sites, so
reality will likely be much more complicated that what is in the
TAFs, but have tried to convey the overall trends. Winds
generally NNW around 10 kt, but could start to back to NNE by
sunrise. Moderate confidence on the overall trends, but low
confidence on the details (especially timing of flight category
changes)

Today....Lower clouds will linger for much of the day. However,
for the I95 TAF sites (KPHL, KPNE, KTTN, and KILG) and the SE
PA sites (KRDG and KABE), the clouds are likely to be on the
cusp of MVFR to IFR, so there is uncertainty on which side of
the threshold the ceilings will be. At KMIV, expect persistent
MVFR ceilings, and at KACY ceilings are likely to be on the cusp
of the IFR to MVFR threshold. Winds should generally settle out
of the NNE at 10-15 kts with some gusts to around 20 kts.
Moderate confidence on the overall pattern, but low confidence
on exactly which flight category the ceilings will be in.

Tonight...This evening, expect similar conditions as what is
prevailing through the day. However, near or after midnight, if
we see any breaks in the clouds, it could be enough for fog to
develop, resulting in IFR or lower conditions. It will be very
localized if it does develop, so low confidence on it occuring
at any one TAF site. NE winds continue, but speeds should
diminish to less than 10 kt. Low confidence.

Outlook...

Friday-Saturday...VFR conditions expected.

Saturday night...VFR conditions early, then MVFR or IFR ceilings
overnight with a chance of showers.

Sunday-Sunday night...MVFR or IFR conditions with a chance of
showers.

Monday...Conditions improving to VFR.

&&

.MARINE...
For the Atlantic coastal waters, expect Small Craft Advisory
conditions to continue today and tonight.

On the Delaware Bay, though there may be some gusts around 20
kt, expect them to stay below 25kt, thus, no SCA conditions are
anticipated at this time.

Outlook...

Thursday night...Small Craft Advisory level seas likely continue
through the night, but winds diminish below advisory levels during
the overnight.

Friday...Small Craft Advisory levels seas may continue into Friday.

Friday night-Saturday night...Conditions remain below advisory
levels.

Sunday-Monday...Small Craft Advisory conditions possible, mainly due
to seas although winds could gust around 20 knots.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ450>455.

&&

$$

SYNOPSIS...Robertson
NEAR TERM...Johnson
SHORT TERM...Robertson
LONG TERM...Robertson
AVIATION...Johnson/Robertson
MARINE...Fitzsimmons/Johnson/Robertson/Wunderlin