877
FXUS61 KPHI 160758
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
357 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. 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, there is a concern for 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, especially if we see any breaks in the
lower clouds. However, much of the guidance that is depicting
favorable profiles for fog development, also appears to be too
aggressive in clearing the low clouds during the day today, so
have low confidence one way or the other.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Ocean storm which has plagued us much of the week may help keep
things a bit drier during the end of the week and weekend as it
lingers off the coast and only crawls further east. This will slow
everything down overall but place a weak blocking ridge over our
region Friday and Saturday. While not guaranteed, especially down in
the Delmarva and further one gets westward into PA, the resulting
blocking high may be enough to keep most of the region dry through
this time. That said, some guidance still dislodges the ridge enough
to bring some showers across the region, starting later Friday night
and continuing into Saturday night, but best chances of rain this
weekend do appear to be more Saturday than Sunday. That having been
said, still a decent chance that areas from Philly north and east,
at least, stay pretty much dry through the weekend. Highs will be
influenced due to persistent cloud cover (which won`t be giving way
so easily) and onshore flow, so while we nudge into the 70s with
some better breaks of sun on Friday, 60s will be common Saturday
again, and with the easterly flow, cut 5-10 degrees off near the
coast. Lows will stay seasonable, with low 50s common.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Next incoming system from the west looks to be shunted south by
the slow moving coastal storm which will linger near Atlantic
Canada Sunday. Thus, odds of precip Sunday look pretty low now,
especially north of Philly, but onshore flow will keep clouds
around and temps cool, with highs mostly in the 60s and cooler
near the coast.

Upper level ridge then tries building eastward across the region
as the aforementioned storm shunted to our south lingers there
early next week. Surface high pressure will build over the
region as well, so expect some clearing and warming, though at
best, temps look likely to return to near normal, as we`ll
retain a threat of some clouds lingering with the surface high
to our north still providing a bit of an onshore gradient. But,
at the very least, Monday and Tuesday look quite dry right now.

Things change Wednesday as the next front approaches from the
northwest. This will bring a returning threat of showers, maybe
even a thunderstorm, but the increased southwesterly flow should
help pump temps up a few more degrees, so a few spots especially
from Philly south and west might reach 80 or so. Lows thru the
end of the weekend into the first half of next week look to be
near 50 to mid 50s for much of the region, mildest Tuesday night
ahead of the front.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Through 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 VFR (especially after 12Z), 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
starting NNW, but 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. That being said,
this is dependent on breaks in the low clouds and guidance that
depicts fog potential in general appears too aggressive in
depicting clearing. Also, it will be very localized if it does
develop. Thus, 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...Mainly MVFR, with local IFR possible. NO SIG WX.

Friday Night-Saturday...VFR/MVFR likely. Chance SHRA.

Saturday Night-Sunday...MVFR/IFR conditions possible. Chance
SHRA.

Sunday Night-Monday...VFR likely. NO SIG WX.

&&

.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...

Friday...Small Craft Advisory on all NJ and DE adjacent ocean
waters with waves of 4-6 feet, subsiding late. Sub-SCA on the
Delaware Bay. Wind gusting no higher than 20 kts all waters.

Friday night thru Saturday night...Mainly sub-SCA. Wind gusts
to 20 kt. Wave heights generally below 5 feet. Chance SHRA.

Sunday thru Sunday night...SCA conditions possible. Wind gusts
to 20 kt. Wave heights up to 5 feet. Slight chance SHRA.

Monday...Mainly sub-SCA. Wind gusts to 20 kt. Wave heights
mainly below 5 feet. NO SIG WX.

&&

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

&&

$$

SYNOPSIS...RCM
NEAR TERM...Johnson/RCM
SHORT TERM...RCM
LONG TERM...RCM
AVIATION...Johnson/RCM
MARINE...Johnson/RCM