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291
FXUS61 KPHI 121412
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1012 AM EDT Sun May 12 2024

.SYNOPSIS...
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Low pressure centered over northern Pennsylvania this morning will
continue to move eastward through this afternoon. High pressure
builds south of the Mid- Atlantic region tonight into Monday.
Another area of low pressure brings more unsettled weather by
the middle of next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Low pressure currently centered over northern Pennsylvania has
an associated occluded front southeast into the Delmarva. Rain
will be most concentrated to the north of the boundary as the
surface low pivots over the New York-Pennsylvnia region.
Scattered showers and drizzle over central Pennsylvania this
morning will move southeastward into greater instability
forecast over the Delmarva by early afternoon. SBCAPE values up
to 500 J/kg will support convective showers and isolated
thunderstorms mainly across the Delmarva and into portions of
southeast PA south of the boundary.

Any shower/thunderstorm activity will quickly wane with the
loss of surface-based instability by early evening. Clouds will
diminish rapidly around 00Z as drier air filters in. Patchy fog
will form overnight with radiational cooling and light winds.
Low temps will be in the 40s.
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&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
Quiet weather makes a brief return with partly sunny skies and
temps warming into the low to mid 70s under broad scale
subsidence for Monday. The brief reprieve ends shortly though
as the ridge breaks down ahead of an advance cutoff low pressure
system moving through the Ohio Valley region. With a modest
surge of PVA and height falls, there should be ample lift to
support fairly widespread showers across the region Tuesday
afternoon through Wednesday. Severe progs aren`t very supportive
so we should be looking at more of the typical spring/summer
showers with maybe a rumble of thunder and brief periods of
moderate rainfall. PW isn`t forecast to be high with respect to
climo as the EFI is remarkable average for the week across the
forecast region. Ensemble guidance suggests about a 40% of
seeing 0.4" or more with only a 15-20% chance of more than an
inch. With rivers back towards normal streamflows and the
rainfall not expected to fall over a short period of time, there
are currently no flooding concerns.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
Heading towards the end of the week the forecast will be highly
dependent on how quickly the low pressure system through the
middle of the week departs. There`s considerable spread in
guidance clusters from the ensemble suites this morning mostly
dependent on timing. So the forecast is subject to change
somewhat dramatically over the next few days until guidance
becomes more consistent. Eventually another system will bring
widely scattered showers but for the given reason just
mentioned, confidence isn`t sufficiently high on whether that is
Sat or Sun. Thus the forecast call for low to moderate changes
(30-40%) both days with slightly higher chances on Saturday.

Temps through the long term should be fairly seasonable in the
low to mid 70s with overnight lows in the 50s most days.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Rest of today...Ceilings 1-2K ft over PA/NJ/northern DE through
mid afternoon then gradually becoming sct 22Z-00Z. Sct- bkn
clouds with bases 3-5K ft over southern DE and Eastern shore MD
will continue rest of the day. Main area of light rain over NJ
and eastern PA will continue through mid afternoon before
dissipating. Scattered showers with potential thunderstorms will
move through Delmarva this afternoon. SE winds around 5-10 kt.

Tonight...Any lingering bkn-ovc ceilings will become few-skc
00Z-02Z. Patchy fog in southeast PA valleys and inland NJ
overnight. Winds light and variable.

Outlook...

Monday through Tuesday...No significant weather expected.

Tuesday Night through Wednesday night...Sub-VFR conditions
expected with occasional showers.

Thursday...No significant weather expected.
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&&

.MARINE...
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No marine headlines are in effect through tonight. E-SE winds around
10-15 kt today will diminish to around 5-10 kt tonight. Seas of 3-4
feet. Scattered rain showers through this afternoon.

Outlook...

Monday...No marine headlines expected.

Tuesday through Wednesday...SCA conditions possible (30-40%) as
wind gusts get near 25 kt. Significant wave heights approach 6
feet Wednesday. Occasional showers.
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&&

.TIDES/COASTAL FLOODING...
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High tide has passed over the Atlantic Ocean however trapped
water in the back bays will slowly empty through this afternoon.

Spotty minor flooding is also expected with tomorrow morning`s
high tide within the Chesapeake Bay.

No further tidal flooding issues are expected beyond this
morning`s high tide.
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&&

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

$$

SYNOPSIS...Deal/Franklin
NEAR TERM...Desilva
SHORT TERM...Deal/Franklin
LONG TERM...Deal
AVIATION...Deal/Desilva/Franklin
MARINE...Deal/Desilva/Franklin
TIDES/COASTAL FLOODING...