Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 281109
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
709 AM EDT Thu Mar 28 2024

.SYNOPSIS...
A slow moving cold front will approach our region from the west
as a wave of low pressure tracks northeastward off the coast
today, resulting in a period of unsettled weather. Weak high
pressure will begin to build in on Friday. A weak clipper
system may move through on Saturday, otherwise fairly quiet and
seasonable conditions will prevail over the weekend. Another
period of rainy weather is expected early next week as low
pressure tracks toward our region from the Ohio Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
No major changes have occurred with the forecast through today. Much
of the area will experience a rainy day with increasing northerly
winds and temperatures near 50 degrees.

Troughing shifting eastward toward the East Coast will amplify by
later today, with broad diffluence across the region aloft. Surface
low pressure across eastern coastal North Carolina this morning will
lift northeastward and eventually offshore later today along a
baroclinic zone in place due to a stalled frontal boundary.
Meanwhile, a subtle cold front will pass southward across the area
and offshore throughout the day.

The strongest forcing with this system will impact the area around
midday as the surface low begins making its closest pass to our
area. This is when more widespread, steadier/heavier rain is
currently anticipated. The rain so far has been fairly periodic in
nature. The system and rain will depart late this afternoon and
evening. The rain may linger near the coast as late as 10 PM to
midnight or so. As of 7 AM, roughly 0.25-0.75" of rain has
fallen across the area. Additional rainfall amounts of
0.10-0.50" are forecast along and northwest of I-95 (greatest
amounts along I-95), and around 0.50-1.50" are forecast across
the coastal plain with the highest amounts likely along the
immediate coast. This rain may lead to additional rises on
creeks, streams, and river across the area, however the
likelihood of any significant flooding with this event is low
(10% or less).

Winds will settle out of the north to northwest today around 5-10
mph. The winds will increase into tonight to near 10-20 mph with
gusts up to 25 mph possible. Temperatures will remain mild in the
40s to near 50s through today, although the cold advection beginning
tonight will drop us back into the mid to upper 30s for low
temperatures by Friday morning.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Friday will feature a return to dry and sunny but windy weather
as a broad upper-level ridge encompassing much of the central
and eastern portions of the United States expands eastward
toward the East Coast. Surface high pressure centered across the
southeastern US with a weak ridge extending northward to the
west of the Appalachians will start to take control, but as
strong low pressure lifts out toward Nova Scotia, a strong
pressure gradient will keep gusty northwest winds across the
mid-Atlantic and Northeast on Friday. Expect gusts of 30 to 35
mph, locally/briefly higher over exposed higher elevations
toward the Appalachians. Temperatures will be fairly seasonable,
gradually moderating heading into the weekend, with lows mainly
in the 30s and highs in the 50s. A weak `clipper` system is
still is projected in the model guidance to pass ESE across PA
toward Delaware Bay on Saturday, along with a weak shortwave
trough. The system will lack much moisture, so while some
scattered showers are forecast to pass through portions of the
area, some spots may end up dry, with less than a quarter-inch
of rain even where showers or a briefly steadier period of rain
does focus in around midday through Saturday afternoon. Westerly
breezes will continue to ease Saturday into Saturday night.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Weak high pressure passing eastward from the Great Lakes across
the Northeast should result in quiet weather on Sunday, and the
overall nicer day of the weekend as milder air continues to
filter in on a westerly breeze. Lows in the 40s should be
followed by highs mainly in the 60s. Some partial sunshine can
be expected, but the sky cover forecast is somewhat questionable
as one shortwave passes by to our north, as a warm front begins
to approach from the Ohio Valley, probably at least resulting in
some high cloudiness around.

Heading into early next week, the weather pattern will turn
increasingly active across the eastern US. An upper-level trough
over the Southwest will eject northeastward, with low pressure
tracking across the Ohio Valley by Tuesday. An approaching warm
front could bring some rain into our region as early as Monday,
but models vary on that timing, so we have just a 30-50 percent
chance of rain right now. Tuesday and Tuesday night, possibly
into Wednesday, looks like the most likely period of wet
weather, as that low pressure area lifts toward the lower Great
Lakes, then transfers to a strengthening coastal low that lifts
northeastward from the northern mid-Atlantic or New England. A
rather potent upper-trough will drop southeastward across the
Great Lakes and possibly phase with the aforementioned trough,
supporting this strong area of low pressure. Will have to
monitor this system for some heavy rain potential, followed by
some gusty winds later Wednesday into Thursday. The greater
impacts though look to target New England, especially northern
portions, where a late-season snowstorm looks likely for them.
Our temperatures will remain seasonably mild, with highs
generally in the 50s and lows in the 40s early through mid next
week.

&&

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE,
KRDG, KILG, KMIV, KACY and surrounding areas.

Through Today...Generally prevailing IFR conditions this morning in
light to moderate rain should gradually improve toward MVFR this
afternoon between 16-20Z. There may be some brief periods of
improvement to MVFR or VFR at times, but this will not be the
prevailing condition through 16Z. Light and variable winds early
will settle out of the north to northwest by late morning near 5-10
kts. Improvement to VFR is forecast for all locations between 20-
00Z. High confidence on restrictions in rain today, and moderate
confidence on the timing of improvements later today.

Tonight...VFR with clearing skies. Northwest winds 10-15 kts with
some gusts near 20 kts possible at times. North to northwest winds
near 2kft increasing to 35-40 kts may lead to some LLWS, but surface
winds should remain elevated enough to preclude a TAF mention. High
confidence.

Outlook...

Friday: Mainly clear and VFR. Windy with gusts to 30 kt.
Saturday: Mainly VFR but at least some mid-level ceilings with a
chance of showers.
Sunday: Mainly VFR and rain-free.
Monday: Chance of rain and possible sub-VFR conditions in both
CIGs and VSBY.

&&

.MARINE...
Rain and fog will restrict visibility to around 1-3 NM for much
of the day and into the evening. North to northwest winds will
increase this evening with wind gusts near 35 kts forecast for a
few hours between midnight tonight and mid-morning Friday.
Thus, the Gale Watch was upgraded to a Gale Warning for tonight
for all Atlantic and Delaware Bay coastal waters. Seas will also
increase to around 4-7 feet tonight.


Outlook...

Friday...In the wake of low pressure lifting out east of New
England, fair but windy weather is forecast, with northwest
winds prompting Gale Warnings overnight into early Friday
morning. If we do have some gale gusts (greater than 34 kt)
across portions of the coastal waters lingering early in the
morning, we have high confidence that those will diminish to
SCA level winds/seas later Friday. However, gusts to 30 kt will
still linger, even across Delaware Bay, with rough seas 5 to 7
ft across the open ocean.

Saturday and Sunday...SCA conditions with respect to both winds
and seas should end by Saturday morning, with westerly winds
around 10-15 kt for the weekend. Chance of light rain later
Saturday, otherwise mainly fair weather. Seas around 3 ft.

Monday...Winds switching to easterly 10-15 kt as a warm front
approaches with a chance of rain. Seas around 3 ft.

&&

.TIDES/COASTAL FLOODING...
The threat of coastal flooding has come to an end, and it looks
like we will continue to have no concerns for flooding through
the weekend. We have been keeping an eye on tide gauges along
the lower Delaware River overnight, but it looks like water
levels are trending a little lower than forecast, so we may not
even see any spotty minor flooding with high tide this morning.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning from 6 PM this evening to 10 AM EDT Friday for
     ANZ430-431-450>455.

&&

$$

SYNOPSIS...Staarmann
NEAR TERM...Staarmann
SHORT TERM...Dodd
LONG TERM...Dodd
AVIATION...Dodd/Staarmann
MARINE...Dodd/Staarmann
TIDES/COASTAL FLOODING...Dodd


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