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602
FXUS61 KPHI 250756
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
356 AM EDT Tue Jun 25 2024

.SYNOPSIS...
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High pressure south and west of the region early this morning moves
eastward and offshore through the day today. A warm front will lift
north of the area early on Wednesday before another strong cold
front passes by late Wednesday night. High pressure returns for
Thursday and continues into early Saturday ahead of another low
pressure system that approaches late Saturday into Sunday. High
pressure returns by early next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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High pressure will shift south of the region Tuesday, but
remain in control and bring fair weather through the day. Mostly
sunny skies and a more WSW wind will allow for temperatures to
warm slightly compared to yesterday with highs expected in the
upper 80s to low 90s. Despite the warmer temperatures, dew
points will remain comfortably in the 50s, giving us a small taste
of that "dry heat" our friends across the western US are used
to.

Come late afternoon/early evening, we will see a weak shortwave
pass overhead. This could be enough to bring some isolated to
scattered light showers across the Poconos, Lehigh Valley, and
northern NJ. That said, it is very possible most of these
showers won`t make it to the surface given the drier conditions
in the low-levels. Otherwise, we can expect a rather uneventful
night, though clouds will be increasing ahead of our next
system. As a result, low temperatures will be warmer, only
cooling off into the low to mid 70s. Dew points will be creeping
up overnight as well, reaching back into the 60s by daybreak.
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&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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SW flow increases for Wednesday ahead of an approaching cold front.
This will lead to hot and humid conditions returning as surface dew
points rise into the upper 60s to near 70 around the region under
continuing mainly sunny skies through the early afternoon. This set
up will lead to the mid 90s for highs across most inland locations.
Closer to the coast and up in the Poconos, temps should remain in
the 80s. Max heat indicies at this time look to reach around 100 for
most areas near and south of the urban corridor (except near the
coast) and so Heat Advisories have been issued.

The other big story will be the potential for severe weather
Wednesday afternoon and evening. An upper trough will swing through
the Great Lakes on Wednesday approaching our area by Wednesday night
with an advancing cold front. With the abundance of moist, humid air
in place, several indicators are present for thunderstorm
development. Forecast soundings show SBCAPE values around 1000-2000
J/kg, bulk shear values around 30 kt, and lapse rates around 7.0-
7.5C/km. Shear values are also a bit modest since forcing will be in
somewhat close proximity. As a result, the Storm Prediction Center
has now outlined our entire forecast area in a SLIGHT Risk (Level
2/5) for severe weather. The main threat should be damaging wind
gusts considering the environment. However given the strong low
level directional and speed shear there will also be the
potential for one or two tornadoes, especially over northeast PA
into NW NJ. In terms of flooding, PWATs will be up around 2
inches, so any storm will be capable of producing heavy
rainfall. Storm motion does appear to be relatively-fast, so not
expecting any widespread flood impacts at this time. In terms
of timing, the latest trends with some of our guidance are
suggesting slightly later timing indicating it could be more of
an evening event. Chances for scattered storms still look to
begin by the afternoon, especially over northern and western
areas, but it may not be until the evening timeframe that more
widespread convection moves through closer to the front. The
cold front will eventually move offshore late Wednesday night
into early Thursday.

Some showers may linger near the coast on Thursday morning, but the
overall trend will be for decreasing clouds and lowering dew points
on Thursday as high pressure starts to build in from the west.
It will feel much more comfortable outside compared to Wednesday
with highs returning closer to normal. The high builds in right over
the area for Thursday night bringing mainly clear skies with light
winds. Expect lows ranging from the mid 50s north to the mid 60s
near and south of the urban corridor.
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&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
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High pressure will be centered just north of the area early Friday
before retreating to the north and east off the coast by later
Friday through Saturday as the next system approaches. This will
result in sunshine for Friday with seasonable temperatures and low
humidity. Generally expect highs in the 80s with dew points in the
50s to low 60s.

As mentioned above, the next system approaches Saturday first
pushing a warm front towards the area and then a cold front by
Sunday as the low moves by to our north. This will bring increasing
chances for showers and storms by Saturday afternoon continuing
Saturday night into Sunday. Not expecting a total washout though as
most areas, even those that see storms, should be precip free the
majority of the time this weekend. The heat and humidity will also
return with max heat indicies Saturday generally in the 90s and
potentially around or over 100 for Sunday.

Following the passage of the cold front late Sunday, cooler and
drier air moves in to start next week.
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&&

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

Early this morning (through 12Z)...VFR. Skies mostly clear.
NW/W winds decreasing to around 5-10 knots. High confid.

Tuesday...VFR. Mostly clear skies. West winds increasing to
around 10 knots and shifting to the southwest after 18Z. High
confid.

Tuesday night...VFR with increasing clouds. No significant
weather expected.

Outlook...

Wednesday through Wednesday night...Primarily VFR. Scattered
thunderstorms during the afternoon and evening which may cause sub-
VFR conditions. Locally gusty winds near/in any thunderstorm.

Thursday through Saturday...Mainly VFR through the period. Chance of
an early Thursday AM shower around ACY and MIV and then chances for
scattered showers and storms arriving Saturday PM.
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&&

.MARINE...
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Conditions will remain below SCA criteria for the first half of
Tuesday before winds begin to ramp up from the SSW tonight,
gusting to around 25 kts for all coastal waters. Seas will
respond as well, beginning at 2-3 feet in the afternoon and
rising to 3-5 feet Tuesday night.

Outlook...

Wednesday through Wednesday night...Small Craft Advisory conditions
expected over the ocean zones with south/southwest winds gusting up
to 25 knots and seas around 4-5 feet. Also, showers and storms
likely over the waters by Wednesday night. Any storms could bring
locally strong winds over 35 knots.

Thursday through Saturday...No marine headlines expected.
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&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...Heat Advisory from 9 AM to 9 PM EDT Wednesday for PAZ070-071-
     102-104-106.
NJ...Heat Advisory from 9 AM to 9 PM EDT Wednesday for NJZ010-012-
     013-015-017>020-027.
DE...Heat Advisory from 9 AM to 9 PM EDT Wednesday for DEZ001.
MD...None.
MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT
     Thursday for ANZ450>453.
     Small Craft Advisory from 11 PM this evening to 11 PM EDT
     Wednesday for ANZ454-455.
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&&

$$

SYNOPSIS...DeSilva/Fitzsimmons/Hoeflich
NEAR TERM...MJL/MPS/OHara/Staarmann
SHORT TERM...DeSilva/Fitzsimmons
LONG TERM...DeSilva/Fitzsimmons
AVIATION...DeSilva/Fitzsimmons/MJL/OHara/Staarmann
MARINE...DeSilva/Fitzsimmons/OHara/RCM/Staarmann