792
FXUS61 KPHI 190514
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
114 AM EDT Fri Jul 19 2024

.SYNOPSIS...
High pressure will prevail through Friday across the region
with a frontal boundary stalling out south of the area. A weak
system passes by Saturday night, then high pressure will remain
offshore through much of next week with daily chances for
showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
In the wake of the cold front which continues to progress
slowly southeastward, away from our region, high pressure will
build in combined with a little bit of dry air advection.
Consequently, will see dewpoints in the 50s (60s near the coast)
by this afternoon, which will be a nice change especially from
the humidity earlier in the week. This is lower than what a
blend of guidance is depicting, but suspect that many components
of the blend may not be capturing how deep the mixed layer will
be. Temperatures will be near normal, with highs generally in
the 80s (though 70s will be possible in the higher terrain of
the southern Poconos and near the coast).

With high pressure building in, expect large scale subsidence to
be in effect, so don`t expect any precipitation, and only few
mid level cumulus clouds through the day. May see more high and
mid level clouds build in Friday night as a weak low pressure
system begins to develop to our southwest.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
The stalled frontal boundary will begin to return northward on
Saturday as a shortwave trough nears the region. The trough and
associated jet streak will pass through overnight Saturday
night, then zonal flow returns by Sunday.

The main story for the weekend will be the return of more
seasonable humidity levels, though not oppressive with dewpoints
rising back up into the mid to upper 60s. Temperatures will
remain seasonable with highs in the mid to upper 80s and lows
mainly in the 60s. Friday night will likely be the coolest for
the foreseeable future with high pressure located overhead. Some
lows in the mid to upper 50s will be prevalent near/north of
I-78. The passing trough will yield an increasing chance for
convection by late Saturday into Saturday night. The question is
how much instability will be around during the overnight period
though since diurnally driven instability will be waning, so we
have advertised mainly 20-40% PoPs for now. Saturday should
also be fairly cloudy with the approaching system, but more sun
can be expected by Sunday. Some lingering convection possible
Sunday across the coastal plain with the boundary remaining in
the vicinity and diurnal instability developing. Severe
thunderstorms are unlikely during this period, but gusty winds
and heavy downpours may be possible.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
The flow remains quasi-zonal into next week with a trough
approaching and upper jet streak increasing by Wednesday and
Thursday. At the surface, Bermuda high pressure remains offshore
and the frontal boundary will lift well north of the area. This
will translate to increasing chances for convection with each
day as synoptic support increases with each passing day.
Generally expect isolated to scattered showers and thunderstorms
each day, favoring the typical diurnally driven hours. Some
severe thunderstorms are possible, though the daily details on
the convective evolution remain unclear. Temperatures will
remain seasonable with highs ranging from the mid 80s to near 90
degrees and lows in the mid 60s to low 70s. Humidity will
increase slightly into next week with dewpoints returning to the
upper 60s to low 70s.

&&

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

Through Today...Mostly VFR conditions with only few cumulus
clouds around 5000 ft AGL developing in the afternoon. The only
exception to VFR is a chance (50%) of localized visibility
restrictions with BR between 09 and 12Z. At this point, KMIV has
the highest risk to see restrictions. It is unlikely to develop
at the other TAF sites. Winds may start northerly or variable,
but should settle out of the west by mid day. A seabreeze after
18Z may cause SE-S winds at KMIV/KACY. High confidence on most
aspects of the forecast. Moderate confidence on BR potential.

Tonight...VFR with increasing high and mid level clouds
especially after 06Z. Winds expected to be light and variable
for much of the night. High Confidence.

Outlook...

Saturday through Sunday...Generally prevailing VFR. A 20-40%
chance of showers or thunderstorms mainly Saturday night. Patchy
fog possible at night.

Monday and Tuesday...Generally prevailing VFR expected.
Scattered showers and thunderstorms likely each afternoon and
evening.

&&

.MARINE...
Winds and seas remain below SCA criteria through Friday. Winds
generally from the SSE around 10 kts or less veer to the N
overnight, becoming NNE around 10-15 kts Friday afternoon. Seas
around 3-4 feet.

Outlook...

Friday night through Tuesday...No marine headlines expected.
Scattered showers and thunderstorms possible Saturday night
through Tuesday, otherwise fair weather.

Rip Currents...

For Friday, winds will become northeasterly but remain around
10 mph. Wave heights will mainly remain around 1-2 feet in
Delaware and 2-3 feet in New Jersey with a 7-8 second period.
Therefore, the risk for the development of dangerous and life
threatening rip currents is forecast to be LOW at the DE beaches
and MODERATE at the NJ shore on Friday.

For Saturday, winds will become southeasterly at 5 to 10 mph.
Wave heights will drop to around 1-2 feet across all coastal
areas with a 6-7 second period. Therefore, the risk for the
development of dangerous and life threatening rip currents is
forecast to be LOW at all coastal areas on Saturday.

For specific beach forecasts, visit weather.gov/beach/phi

&&

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

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...Johnson
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...Johnson/Staarmann
MARINE...MJL/Staarmann