205
FXUS61 KPHI 171851
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
251 PM EDT Fri May 17 2024

.SYNOPSIS...
As low pressure continues to move farther away from our area through
tonight, another area of low pressure slides to our south over the
weekend. High pressure then builds across our area early next week
before shifting to our south. A cold front then moves through
Thursday into Friday.

&&

.NEAR TERM /THROUGH SATURDAY/...
Clouds have been slow to lift/thin across the area so far this
afternoon, but latest trends are showing that it is stating across
the North/Northeast areas. Some improvements to partly sunny are
expected into the evening. After that, increasing high/mid clouds
overnight as the next system approaches. Scattered showers are
possible for the western areas overnight. Many of the models
have the rains decreasing overnight. Patchy fog is possible
overnight. Lows will drop into the low/mid 50s for most spots with
some upper 50s for metro Philadelphia. Winds will be light tonight.

On Saturday, a disorganized short wave will move from the upper Ohio
Valley across the Middle Atlantic region. A weak surface low will
accompany the feature. Clouds will have the upper hand much of the
day and scattered to numerous showers will be across the area.
Better chances for rains will be across Delmarva, south NJ and up
into Berks County PA. These areas will be close to the better lift
associated with the low/short wave. It`ll remain cool with the
clouds and rains, so high temperatures will likely only climb into
the low/mid 60s. Winds will be light from the East or Southeast much
of the time.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Surface high pressure extends southward into our area later Saturday
night and Sunday, with most of the energy now confined to the south
of the area which will help to completely end the shower chances
after Saturday evening. Some lingering low-level moisture though and
especially if the clouds clear enough may result in patchy fog
Saturday night into early Sunday. By Sunday afternoon, expect at
least some sunshine to make a return. High temperatures top out into
the 70s for many inland areas, although a lingering onshore flow
will keep it much cooler closer to the coast.

As an upper-level ridge starts to build over the area Monday,
surface high pressure becomes more centered across our region. The
increasing subsidence and drier air should assist in less cloud
cover for much if not all of the region. The air mass will continue
to modify and therefore afternoon high temperatures are forecast into
the 70s again for much of the area. A northeast wind though should
turn east to southeast as a sea breeze becomes more established and
this will yet again keep it much cooler closer to the coast
Monday.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Summary...Above average temperatures and dry to start, followed by
some chances for showers/thunderstorms with a cold front. Some
cooling then possible Friday.

Synoptic Overview...An upper-level ridge is forecast to be across
much of the East Tuesday before it shifts offshore Wednesday. An
upper-level trough tracking eastward from south-central Canada to
the mid-Mississippi Valley will drive surface low pressure well to
our north. A cold front however is forecast to arrive across our
area Thursday into Friday as the upper-level trough mostly glances
the Northeast. The flow aloft then may turn more zonal into Friday,
although a shortwave trough in the Tennessee Valley may make a run
at our area later Friday. The latter is much more uncertain at this
time range.

For Tuesday and Wednesday...Given the presence of upper-level
ridging overhead Tuesday along with high pressure at the surface, a
warmer air mass will be in place. The light winds however should
result in a sea breeze Tuesday afternoon which will then make a run
inland keeping it cooler closer to the coast. This setup is expected
to result in no precipitation and a decent amount of sunshine given
the subsidence. As we go through Wednesday, more of a return flow
should become established as the ridge aloft and also the surface
high shifts offshore. Low-level warm air advection should increase
some with this southerly flow ahead of an upper-level trough which
drives surface low pressure and a cold front. The forward
motion/timing of the cold front is less certain especially as the
main upper-level trough may just glance the Northeast and the
surface low tracks well to our north. It is possible a band or
broken band of showers and thunder makes it into our far western
zones late Wednesday tied to a surface trough. Given the initial
subsidence and favorable setup, temperatures were bumped up some
especially away from the coast.

For Thursday and Friday...The aforementioned upper-level trough
glances our area Thursday however a cold front tied to low pressure
well to our north should move through sometime during this time
frame. There looks to be enough forcing to produce some showers and
instability should be sufficient during the afternoon and evening
Thursday for some possible thunderstorms. The warmth (and more
humid) may peak Thursday ahead of the cold front with widespread low
to mid 80s for highs, although probably cooler closest to the coast
due to a southerly wind. As of now, the cold front should be
offshore to start Friday with some cooling in its wake. The cooling
does not look all that significant at this time given the weakness
of the upper-level trough and it tending to just glance our
region.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Tonight...Any improvements in the 18Z thru 00Z period will
continue into the early overnight with VFR in many areas but
MVFR also possible. Later tonight, increasing clouds will
develop over the area with a lowering of CIGS into lower-end
MVFR probable. Light E/NE winds early then mostly SE overnight.
Winds speeds mostly 5 knots or less overnight. Low/medium
confid.

Saturday...IFR or low-end MVFR much of the day with showers
across most areas into the late afternoon. Light SE winds much
of the day. Low/medium confid.

Outlook...

Saturday night and Sunday...Areas of MVFR conditions possible with
lingering showers Saturday evening, then VFR overall.

Monday through Wednesday...VFR overall.

&&

.MARINE...
Low-end SCA conditions continue on the northern/central ocean waters
with seas 5 to 6 ft at the buoys. Winds remain mostly N or NE around
10 knots. Cloudy conditions with perhaps a little drizzle at times.
We`ll carry the SCA flag into the evening with the 6PM expiration
time working out well for the northern/central areas. We`ll cancel
the SCA for the srn NJ/DE ocean zones. SCA is not expected Saturday.
Fair tonight and then showers for Saturday. There is a better chance
for showers across the southern NJ and Delaware waters as well as
Delaware Bay.

Outlook...

Saturday night through Wednesday...The conditions are anticipated to
be below Small Craft Advisory criteria.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...High Risk for Rip Currents until 8 PM EDT this evening for NJZ014-
     026.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for
     ANZ450>452.

&&

$$

SYNOPSIS...Gorse
NEAR TERM...OHara
SHORT TERM...Gorse/RCM
LONG TERM...Gorse
AVIATION...Gorse/OHara
MARINE...Gorse/OHara