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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 151933
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
333 PM EDT Mon Apr 15 2024

.SYNOPSIS...
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A slow moving front inches south of the Delmarva tonight. High
pressure builds back in tonight through Tuesday, before a series
of frontal boundaries and low pressure systems affect the East
coast Wednesday through early next weekend.
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&&

.NEAR TERM /THROUGH TUESDAY/...
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This evening, a Severe Thunderstorm Watch has been issued for
southern/central Delaware and the adjacent counties of the eastern
shore of Maryland until 10PM. The activity moving out of DC metro
area and the hills of MD has developed hail cores and gusty winds
will accompany it as well. The activity should remain scattered, but
locally intense. Other areas will have mostly sunny skies and mild
temperatures into the evening. Readings in the upper 70s/low 80s
this afternoon will fall back thru the 70s this evening.

Tonight, the remaining showers or tstms over Delmarva this evening
will diminish by midnight and fair weather is expected after that.
Skies will become clear across the south and remain mostly clear
north/west. The overnight lows will drop to the low/mid 40s for the
N/W areas and only fall into the low 50s for south NJ and Delmarva.

On Tuesday, upper ridging will continue over the area as a surface
high moves southeast from the Great Lakes. Fair weather is expected
with mostly sunny skies expected. high temperatures will be a little
above normal with highs in the upper 60s to low 70s for most spots.
A decently dry airmass too with dew points in the upper 30s/low 40s.
Winds will be mostly West at 5 to 10 mph.
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&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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Upper level ridging will slide eastward toward our region
Tuesday night. This should limit coverage of showers despite a
warm front approaching from the south. Lows in the upper 40s to
low 50s.

On Wednesday, the shortwave ridge weakens ahead of the next
closed low approaching from the west, leading to increasing
chances for showers though the day. Thanks in large part to the
warm front in the region, there will likely be a robust
temperature inversion through the day, resulting in limited
instability. Therefore, not expecting any thunderstorms at this
time. Daytime highs will only be in the low to mid 60s.

The closed low and a trailing cold front approach the region
Wednesday night into Thursday. Consequently, there are chances
for widespread showers and thunderstorms in the Wednesday
night/Thursday period. As far as thunderstorms, instability,
especially surface based instability may remain limited through
this period, so it is uncertain how widespread the coverage of
storms will be. At this point, it appears as if we are likely to
have widespread showers with some embedded thunderstorms,
primarily late Wednesday night into Thursday morning, though
there still remains quite a bit of uncertainty with the timing.

For the rest of the day Thursday, global guidance is showing the
potential for a backdoor front arriving as high pressure off the
coast of Maine interacts with a weak coastal low off the
Delmarva seaboard that will spin off from the decaying parent
cold front from the previous night. Resultant E to NE flow will
help keep temperatures much cooler than earlier in the week.
Depending on how far south this backdoor front advances,
temperatures to the north will be in the 50s with mid to upper
60s to the south.
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&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Tranquil weather should return again, albeit briefly, as the low
departs our region Thursday night into Friday, before the next cold
front approaches to start the weekend. At this point, the forecast
has rain chances almost throughout this period (Friday night through
Sunday), but it is unlikely to be a washout through the period,
rather there remains uncertainty in the exact timing of the cold
front. Once the cold front passes, we should have drying conditions.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

This afternoon...VFR expected. Scattered showers or tstms are
possible across Delmarva and south-most NJ. While I added some VCSH
in for KILG recently, the showers are probably not going to affect
KMIV/KACY. Southwest or West winds around 10 knots gradually
shifting NW late. A few gusts to 20 kts possible. High confid mostly
but medium confid regarding shower/tstm placement.

Tonight...VFR expected. Except for some evening cloudiness for
Delmarva and south NJ, mostly clear skies overnight. Northwest or
North winds 5 to 10 knots. High confid.

Tuesday... VFR expected with few clouds overall. Northwest winds 5
to 10 knots developing. Winds will switch to West or Southwest late
in the day. Medium/high confid.


Outlook...

Tuesday night...VFR expected.

Wednesday through Thursday...There is a good chance (50 to 60
percent) for sub VFR conditions at times due to stratus and showers.
The best chances for this look to be overnight Wednesday night into
Thursday morning.

Thursday night through Saturday...VFR likely, but a brief
period of sub- VFR is possible (20%) especially Friday.
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&&

.MARINE...
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A Severe thunderstorm Watch is in effect for land areas adjacent to
Delaware Bay (Delaware) and out south-most coastal ocean zone.
Scattered tstms with higher winds and seas are possible thru the
early evening for those areas. Other than that, winds and seas will
remain below SCA levels as a weak front passes the waters this
evening. High pressure builds in behind it for Tuesday.

Outlook...

Tuesday night through Wednesday...winds and seas should stay
below SCA criteria.

Wednesday night through Friday...SCA conditions possible for at
especially over our northern ocean zones as winds and seas build.

Friday night through Saturday...Sub-SCA conditions expected.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...Fitzsimmons/MJL
NEAR TERM...OHara
SHORT TERM...Fitzsimmons/MJL
LONG TERM...Fitzsimmons/MJL
AVIATION...MJL/OHara
MARINE...MJL/OHara