750
FXUS61 KPHI 181332
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
932 AM EDT Fri Oct 18 2024

.SYNOPSIS...
High pressure will be in control through the middle of next
week, bringing a period of above normal temperatures. A cold
front will move in for the midweek period, bringing more
seasonable temperatures, though not much in terms of much-needed
rain.

&&

.NEAR TERM /THROUGH TONIGHT/...
Anomalously strong ridging will be building in from the west as
the day progresses. 500 mb heights will be on the order of 2-3
sigma above climo into tonight. At the surface, strong, expansive,
and dry high pressure will also build in from the west, strengthening
to an impressive ~1036 mb overnight across eastern PA. The strong
ridging building in will push the nearby coastal storm well out to
sea through tonight.

The strong subsidence from the ridging, sunny skies, and northerly
breeze should promote efficient boundary layer mixing into the
afternoon. Afternoon high temperatures are forecast to be mainly
in the upper 60s to near 70 degrees area wide. Winds should be
slightly less gusty than Thursday, although we will still have a
sustained 10-15 mph northerly breeze.

BUFKIT and raw model dewpoints indicate we should see dewpoints
mixing out into the 20s today, although dewpoints near/north of
I-78 likely remain closer to 30 degrees where downsloping is
less of a factor. Appears to be a pretty decent setup for
downsloping (dewpoints mixing out and temperatures over-
performing a bit) in our area across the I-95 corridor and
coastal plain with the strong subsidence, northerly breeze, and
sunny skies. So dewpoints in the 20s combined with temperatures
nearing 70 degrees should get us relative humidity values in the
low 20% territory, perhaps upper 10s locally. See the Fire
Weather section below for more details.

For tonight, the center of the strong high will be within the
vicinity of the area, so winds will become 5 mph or less under
clear skies. Given the airmass modification, we should see
temperatures slightly warmer than this morning. Low temperatures
are forecast to range from the upper 30s to mid 40s. Some
patchy frost could develop in the typical colder spots, but the
warmer temperatures should preclude a need for any frost
headlines.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
An abundance of sunshine and above normal temperatures is
expected for this weekend as an area of high pressure will be
directly overhead. Not much to speak of but the combination of
strong high and building heights aloft will result in daytime
highs in the low to mid 70s on Saturday and mid to upper 70s on
Sunday. A perfect weekend to get outside and enjoy some autumn
activities.

For both Saturday and Sunday Night, the surface high overhead
will result in favorable radiational cooling conditions. Think
the airmass will be just warm enough to preclude frost
development for where the growing season is still active, with
lows in the upper 30s/low 40s on Saturday Night. No concerns for
Sunday night as lows will be in the low to mid 40s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Next week will start out dry as an expansive area of high
pressure will be in place. Above normal temperatures are
anticipated as well (upper 70s and maybe even low 80s) and it
will be a set of very nice days to start the week, though we
probably could use some rain at some point.

A cold front looks to come in at some point during the middle
of next week, but global deterministic guidance and ensembles
show little, if any rain associated with the frontal passage.
Rather high confidence in this not being a drought buster,
rather just a few showers around somewhere in the late
Wednesday/Thursday timeframe as guidance differs on the timing
of the front.

Regardless, the front that eventually comes in after Wednesday
will knock down temperatures to more seasonal levels (low to mid
60s) for the end of the week, though the prolonged dry spell
looks to continue.

&&

.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...VFR/SKC. North-northeast winds increasing to near 10-12
kts through 18Z, diminishing slightly thereafter. A few gusts
up to 18 kts possible at times at MIV/ACY. High confidence.

Tonight...VFR/SKC. North winds 5 kts or less to locally calm.
High confidence.

Outlook...

Saturday through Tuesday...VFR. No significant weather.

&&

.MARINE...
Small Craft Advisory remains in effect for all Atlantic coastal
waters through tonight, and through noon today for lower
Delaware Bay. North to northeast winds 15-25 kts with gusts of
25-30 kts will continue through today, gradually lessening into
this afternoon and tonight as the offshore storm pushes farther
out to sea. Seas across the Atlantic waters ranging from 5-8
feet. Aside from the stronger winds and elevated seas, fair
weather is expected.

Outlook...

Saturday through Saturday Night...A Small Craft Advisory is in
effect for all ocean zones as seas will be around 5 to 7 feet.
No marine headlines expected on Delaware Bay.

Sunday through Tuesday...No marine headlines expected.

&&

.FIRE WEATHER...
Very dry conditions are expected today with forecast minimum
relative humidity values in the 20-25% range across much of the
area. Relative humidity in the Philadelphia metro area, southern
New Jersey, and Delmarva could dip into the upper 10s. This
will be combined with winds sustained near 10-15 mph from the
north to northeast, with some sporadic gusts near 18-20 mph
possible at times along and southeast of I-95. High temperatures
will be in the upper 60s to near 70 degrees in most areas under
sunny skies.

After coordination with our forest fire partners, a Special
Weather Statement for fire spread danger has been issued to
highlight this threat. The winds will likely fall short of Red
Flag criteria.

Dry conditions are forecast to persist over the weekend with
minimum relative humidity values around 25-35%, however winds
will be much lighter around 5 mph for much of the area. This
should help limit fire spread potential despite the persistently
dry air.

&&

.TIDES/COASTAL FLOODING...
Persistent and prolonged northerly flow associated with a
coastal low offshore in combination with the Full Moon phase
occuring yesterday will result in higher than normal
astronomical tides for locales through at least Saturday.

This morning will bring the highest tides, though still
expecting only minor tidal flooding at this time. A Coastal
Flood Advisory is in effect for all coastal counties in New
Jersey and Delaware as well as counties along Delaware Bay.
Another advisory may be needed for tomorrow morning`s high tide
but will wait to see how high water levels get this morning
before issuing/extending any headlines.

No tidal concerns are expected for the Delaware River and
Chesapeake Bay communities at this time.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Advisory until 1 PM EDT this afternoon for
     NJZ012>014-020>027.
DE...Coastal Flood Advisory until 1 PM EDT this afternoon for
     DEZ002>004.
MD...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ431.
     Small Craft Advisory until 6 AM EDT Sunday for ANZ450>455.

&&

$$

SYNOPSIS...Hoeflich
NEAR TERM...DeSilva/Staarmann
SHORT TERM...Hoeflich
LONG TERM...Hoeflich
AVIATION...Hoeflich/Staarmann
MARINE...Hoeflich/Staarmann
FIRE WEATHER...
TIDES/COASTAL FLOODING...