Area Forecast Discussion Issued by NWS Mt. Holly, NJ
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000
FXUS61 KPHI 261709
AFDPHI
Area Forecast Discussion
National Weather Service Mount Holly NJ
109 PM EDT Tue Mar 26 2024
.SYNOPSIS...
Strong high pressure centered across the Canadian Maritimes
extends southwestward across our area. This will remain in place
through tonight. Meanwhile, low pressure continues to meander
around well offshore. A cold front is forecast to cross our region
tonight, then it becomes nearly stationary along the coast. Low
pressure tracks northward along this front Thursday and Thursday
night before moving out to sea on Friday. A weak clipper system
may move through on Saturday.
&&
.NEAR TERM /THROUGH TONIGHT/...
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High pressure centered over the Canadian Maritimes, with a
ridge extending southward along the East Coast to the Carolinas
will remain in control of our weather today. This will join
forces with an upper-level ridge also amplifying along the East
Coast, to result in continued dry and stable conditions through
sunset.
A layer of lower clouds across NJ/ern PA earlier thinned out and
moved to the NW earlier. Breaks across NJ lately are beginning
to decrease in size as another batch of low clouds over the
ocean are starting to track/form back into our area. Adjustments
to temps/dewpoints and winds were made for the latest update.
As we head into tonight, low pressure lifting across Lake
Superior will send a cold front toward the Appalachians by
Wednesday morning, while the trailing end of a weak warm front
will near northwestern portions of our region. CAMs and the NAM
are more bullish with at least some light showers pushing in
during the predawn hours Wednesday, perhaps amounting to a few
hundredths of an inch of rain by sunrise from northwest of
Reading to Allentown. As ceilings lower and boundary layer
moisture increases with continued light onshore flow, some
patchy mist or light fog may develop in spots toward morning,
but visibility should stay at or above 1 to 3 miles. It will be
a mild night, with lows staying in the 40s.-- End Changed Discussion --
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Troughing across the Southwest will amplify and shift eastward
this week toward the East Coast by late Thursday. Some subtle
jet dynamics will be at play with a developing low pressure
system, which will have implications on direct impacts we
receive from the system Wednesday through Thursday night.
Surface low pressure should develop across the Southeast
Wednesday and then lift northeastward and eventually offshore on
Thursday along a baroclinic zone in place due to a stalled
frontal boundary. The latest trend in some of the deterministic
and ensemble guidance was for a farther eastward and thus drier
solution. However, the synoptic forcing modeled does not exactly
support this trend. There was no significant changes to the
forecast with this update aside from some adjustments to the
PoPs.
Some areas of light rain should develop on Wednesday, primarily
inland where PoPs are higher during the daytime. This will be
in response to the initial height falls and diffluence aloft.
Stronger forcing will arrive late in the night and especially by
early Thursday as the surface low begins making its closest
pass to our area. This is when more widespread, steadier/heavier
rain is currently anticipated. The system and rain will depart
late Thursday and Thursday night. Currently, QPF ranges from
0.5-1" in the far interior areas of eastern PA and northwest NJ,
to 1-1.5" along I-95, to near 2" along the coast. This forecast
is subject to change though, given the aforementioned subtle
synoptic features at play. This will have implications on an
impacts due to flooding as soils remain very saturated from the
weekend rain. This rain may lead to additional rises on creeks,
streams, and river across the area.
Winds will be light on Wednesday favoring an easterly
direction. As the departing system strengthens and high pressure
pushes into the area, winds will then settle out of the north
to northwest on Thursday and increase into Thursday night to
near 15-20 mph with gusts up to 35 mph possible. Temperatures
will remain mild in the 40s and 50s for much of this period,
although the cold advection beginning Thursday night will drop
us back into the mid to upper 30s.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
Long wave ridging building across the central CONUS should
result in seasonable temperatures and relatively benign weather
conditions this weekend into Monday of next week. A quick moving
shortwave trough may impact the area Saturday with a 20-30%
chance of rain and increasing clouds, however it will not be the
washout last Saturday was. The next system looks to impact the
area late Monday into Tuesday with more widespread rain
possible.
&&
.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...
Tonight... Lower CIGS expected to increase over the area this
evening and continue overnight. MVFR then IFR expected most sites
after midnight. While no VSBY issues are expected for most sites,
some fog may develop closer to the coast, so we`ve included some
KACY/KMIV with low/medium confid. Light East to Southeast winds
overnight.
Wednesday... Low confid with a decent possibility of CIGS becoming
VFR again (like today). We`ll probably offer some improvement to
MVFR after 14Z/15Z again with limited confid. Lower conditions
likely during the afternoon with rains arriving SW to NE. Light NE/E
winds expected.
Outlook...
Wednesday through Saturday...Overall, periods of sub-VFR conditions,
mostly Wednesday through Thursday evening in periods of moderate
to heavy rain late Wednesday through Thursday. VFR returns on
Friday. Scattered SHRA may result in brief sub- VFR conditions
Saturday. Light east winds on Wednesday becoming 10-20 kts and
gusty from the north to northwest Thursday through Saturday.-- End Changed Discussion --
&&
.MARINE...
Some gusts to around 20 kt or so may continue early this
morning around the mouth of Delaware Bay, but conditions will
remain below Small Craft Advisory criteria today. Meanwhile,
winds will continue to gust to 25 kt or so through early this
morning across the open ocean, but gradually ease through this
evening.
However, a large storm well offshore will meander today. Along
with the elevated, albeit lessening northeasterly winds, a substantial
easterly swell will persist today, with seas of 8-12 ft much the
day, only gradually lowering into the 5-8 ft range later tonight.
Small Craft Advisories will remain up as a result.
Outlook...
Wednesday through Saturday...SCA conditions continue into at least
Wednesday due to elevated seas, then seas diminish Wednesday night.
A storm will develop and lift along the coast Wednesday night through
Thursday night, departing on Friday. Strong NW winds develop Thursday
night and continue into Saturday. SCA conditions expected with
marginal gales possible on Friday.
&&
.TIDES/COASTAL FLOODING...
A low pressure system lingering well off the coast will result
in an extended duration of long period swells and rough surf
impacting the Atlantic coast through early this week.
Widespread minor flooding has occurred with the nighttime high
tide, including the tidal Delaware River. This may be due to
increasing fresh water inflow from the recent heavy rains.
Elsewhere, tidal surges remain around 2-3 feet above normal,
though many stations are closer to 2 feet rather than 3 feet.
This resulted in a lack of moderate flooding that was forecast
with the previous high tide, likely owing to underwhelming
northeast winds across much of the coastal waters earlier Monday.
Widespread MINOR flooding is forecast to occur with at least the
next two high tides through tonight and early Wednesday morning.
For the eastern shore of the Chesapeake Bay, tidal surge
anomalies will continue to rise to near 2-3 feet above normal by
Wednesday morning, which is also forecast to result in
widespread MINOR tidal flooding with the Wednesday morning high
tide. Coastal Flood Advisories were expanded to include the
tidal Delaware River and eastern shore of the Chesapeake Bay,
and are now in effect for all tidal areas in the forecast area
to cover the impacted high tides.
Tidal surge anomalies are forecast to begin receding by late
Wednesday. This combined with a lessening influence of the
offshore storm and moving further away from the full moon are
forecast to result in a cessation of coastal flood impacts.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory until 7 AM EDT Wednesday for PAZ070-071-
106.
NJ...Coastal Flood Advisory until 4 AM EDT Wednesday for NJZ016.
Coastal Flood Advisory until 2 AM EDT Wednesday for NJZ012>014-
020>027.
Coastal Flood Advisory until 7 AM EDT Wednesday for NJZ017>019.
DE...Coastal Flood Advisory until 4 AM EDT Wednesday for DEZ001.
Coastal Flood Advisory until 2 AM EDT Wednesday for DEZ002>004.
MD...Coastal Flood Advisory from 8 AM to noon EDT Wednesday for
MDZ012.
Coastal Flood Advisory from 5 AM to 10 AM EDT Wednesday for
MDZ015-019-020.
MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ450>455.
&&
$$
SYNOPSIS...Gorse/MPS
NEAR TERM...Dodd/OHara
SHORT TERM...Staarmann
LONG TERM...Staarmann
AVIATION...Dodd/MPS/OHara
MARINE...Dodd/MPS/OHara
TIDES/COASTAL FLOODING...