-- Discussion containing changed information from previous version are highlighted. --
532
FXUS61 KPHI 121046
AFDPHI

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

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

&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 6:45am...Forecast is running on track. Adjusted PoPs and
temperatures basis current observations. Otherwise, the previous
discussion remains per below:

Low pressure currently centered near Buffalo NY extends a warm front
southeast across Central PA into the Delmarva region. Also, a
trailing cold front is currently positioned along the Appalachians.
The overall position of the warm front will not change as the
front weakens and essentially becomes a stationary boundary near
the Delaware Bay. To the north of the boundary, this is where I
expect the highest probability of light rain to continue
through the morning as the surface low pivots near the eastern
Great Lakes. Periods of drizzle and mist will also be possible
up in the Lehigh Valley/Poconos, as southeast flow results in
some upsloping effects. For areas south of the boundary, precip
will be more in the way of isolated to scattered showers after
daybreak.

By the afternoon, the cold front will be making its way east across
the Mid-Atlantic. As it does so, there will be some shortwave energy
aloft rounding the base of the upper trough which looks to spark up
some showers and possibly a couple thunderstorms this afternoon.
SBCAPE values up to 500 J/kg will be available to tap into basis
available forecast soundings. As a result, have introduced a slight
chance of thunder in the forecast mainly across the Delmarva and
into portions of southeast PA south of the stalled boundary. In
total, expecting rainfall amounts up to 1/2 of an inch areawide.
High temps will range from the mid to upper 50s for most, with low
to mid 60s across the Delmarva.

Any shower/thunderstorm activity will quickly wane with the
loss of surface-based instability by early evening. Latest HREF
guidance suggests that skies will vastly improve around sunset
or so as some drier air filters in. Overall, an improvement in
conditions is expected tonight as the upper trough moves away.
Will need to monitor the potential for some patchy fog late as
well. Low temps will be in the low to mid 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 /12Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...Generally expect a mixture of MVFR/VFR CIGs at all
terminals today. The highest likelihood of MVFR CIGs will be
after 14Z. Scattered showers with potentially a thunderstorm
near KILG/KMIV this afternoon. SE winds around 5-10 kt.
Moderate confidence.

Tonight...Any lingering sub-VFR CIGs early, should give way to
clearing skies as skies scatter out by 23Z-00Z. Some increase
in low-level clouds will be possible early Monday especially
near KRDG/KABE with some patchy fog possible. Winds light and
variable. Moderate confidence.

Outlook...

Monday through Tuesday...No significant weather expected.

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

Thursday... VFR probable.
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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. Other than some scattered rain showers continuing into
this afternoon, fair weather is expected.

Outlook...

Sunday night through Monday...No marine headlines expected.
Fair.

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...
Coastal Flood Advisories continue for the Delaware River and
along the back bays of Ocean, NJ and Sussex, DE this morning.
High tide has passed over the Atlantic Ocean however trapped
water in the back bays is pushing sites well into minor flood
stage this morning.

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.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None.
NJ...Coastal Flood Advisory until 9 AM EDT this morning for NJZ020-
     026.
DE...Coastal Flood Advisory until 9 AM EDT this morning for DEZ003-
     004.
MD...None.
MARINE...None.
-- End Changed Discussion --

&&

$$

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