682
FXUS61 KPHI 080825
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
415 AM EDT Wed May 8 2024

.SYNOPSIS...
An area of low pressure tracks by to our north early this morning.
This will be followed by a stronger area of low pressure moving
across the region Thursday. This low will track east of the area
Friday with additional upper level disturbances tracking through the
area this weekend. A warmer, drier pattern looks to return early
next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
250 AM...As of early this morning a warm front associated with an
area of low pressure over the Great Lakes was lifting north of the
region. Meanwhile, an area of showers/storms closer to the center of
the low and ahead of the system`s cold front was approaching from
western PA. Some of these have been strong to severe given the
strong shear and forcing associated with the environment despite ML
CAPE only being around 500 to 1000 j/kg. There has also been some
mist, fog, and areas of low stratus that have developed across the
region as we get into the warm sector of the approaching system with
light southerly winds.

As we go through the latter part of the overnight into Wednesday
morning, showers/storms move eastward and should enter the region by
around the 5 to 6 AM time frame. The trend should be for them to
generally weaken as they approach but that said, some of them could
still produce some gusty winds in addition to heavy rainfall. This
could bring a quick quarter to half inch or so of rain in spots.
Also, the timing of these shower/storms moving through right around
first part of the morning will not be ideal for the morning commute.
The good news is that the precipitation will be moving through
pretty quickly and be out of the area by around mid morning as it
moves off the coast. Otherwise, the clouds will diminish by the
afternoon allowing temperatures to rise quite a bit. Highs will be
the warmest of the week, with temperatures ranging from the upper
70s well north and west to the mid to upper 80s south away from the
cooler waters. It will become breezy with southwest to west winds
gusting 20-25 mph. Earlier it had looked like we could see some
additional isolated storms in the afternoon but at this point it
looks quite dry through the column so we keep afternoon POPs below
15 percent. That said, if something did manage to form it could
produce gusty winds given inverted-V soundings.

As we head into Wednesday night, initial area of low pressure
continues moving east off the coast of New England and out to sea.
This will push a weak cold front offshore through the evening.
Meanwhile by the overnight period the next wave of low pressure will
be approaching as it moves eastward through the midwestern states
and this will start to push the front back to the north as a warm
front. Clouds will once again be on the increase by the late
overnight and it`s possible we could see some showers start to enter
the region towards dawn, however the trend has been slower with
these arriving later. Expect lows ranging from the 50s north to the
low 60s south.

Thursday is still shaping up to be more unsettled as this next area
of low pressure referenced above moves across the region bringing
additional rounds of showers and storms. What`s worth noting though
is that the model guidance continues to trend farther south with the
track of this system...likely tracking the low east through Delmarva
or perhaps even slightly to the south of here. This should tend to
limit the threat for severe weather Thursday afternoon to Delmarva
and perhaps extreme SE PA and southern NJ. Confidence on exactly
where this threat sets up though is still not that high as there
could be further changes to the track of the low. If it keeps
trending farther south, this could keep the severe weather threat
even south of Delmarva while a trend back to the north would allow
the warm front to get farther north into PA and NJ leading to a more
expansive severe threat. Right now the Storm Prediction Center has
Delmarva in a SLIGHT risk for severe storms for Thursday with a
narrow area of a MARGINAL risk north of here clipping SE PA and
southern NJ. One thing to point out though is that both speed and
directional shear will be quite strong near the track of the low so
if there is enough instability that makes it into the area, all
threats will be on the table...Damaging winds, large hail, and even
the potential for a tornado or two. The clouds and showers/storms
will keep it cooler for Thursday with highs generally in the 70s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
With an overall slower trend with the system, showers/storms could
last through a good portion of Thursday night (PoPs mainly 55-65
percent) although any severe weather threat should diminish through
the nighttime hours with the loss of daytime heating. Lows generally
in the low 50s.

On Friday, our earlier low pressure will track east of the region
while an upper level trough axis lags behind and pushes through the
mid Atlantic. This will keep chances for showers in the forecast,
especially north (POPs ranging from around 40 percent south to 60
percent north), under generally overcast skies. It will also be
cooler with highs mostly in the upper 50s to mid 60s. Shower chances
continue into Friday night but should gradually diminish as the
upper level trough pushes through later overnight. Lows mainly in
the mid-upper 40s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
In the big picture, the weather pattern will remain on the unsettled
side through the weekend as a long wave upper level trough lingers
in the east. This should be followed by a drying trend into early
next week. Heading into Saturday, chances for showers diminish, as
the initial shortwave trough moves out and shortwave ridging builds
in briefly for a time. However by late day the next disturbance will
be approaching and this could bring some more showers back into the
region, especially over eastern PA. So we keep the mention of shower
chances in the forecast but POPs are generally only in the 20 to 30
percent range. Expect highs mainly in the 60s under a mix of sun and
clouds so certainly not a washout. A better chance for showers
arrives Saturday night into Sunday as the next shortwave trough
swings through (POPs 30 to 50 percent) and there will also be more
in the way of cloud cover.

Finally by early next week it should start to trend warmer (highs
mainly in the upper 70s) and drier (PoPs generally less than 25
percent) as the upper trough moves out and the flow over the east
becomes more zonal.

&&

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

Through Wednesday...Showers with the risk of embedded thunderstorms
arrives west to east around the 9-12z time frame. These should be
weakening with time though and it`s possible little in the way of
precip occurs near the coast at ACY. Generally expect lowering cigs
and visbys though through around 11-12z with most sites seeing
conditions go to MVFR with IFR to even LIFR likely at MIV and ACY.
Showers/storms should quickly move out by around mid morning with
improvement to VFR at this time. Southerly winds around 5 knots
through 12z becoming SW to west through Wednesday at 10 to 15
gusting 20 to 25 knots. Moderate confidence overall.

Wednesday night...Mainly VFR with winds becoming light and variable.

Thursday...Additional rounds of shower/storms likely along with
lowering cigs and visbys down at least MVFR at times. Winds
generally east around 10 knots.

Outlook...

Thursday night through Sunday...Sub-VFR conditions favored at night
in fog/mist and stratus, while VFR conditions overall during the day
for most days. Chances for SHRA/TSRA throughout the period with sub-
VFR conditions.

&&

.MARINE...
Conditions will remain below Small Craft Advisory levels through the
day today but expect some fog over the waters through the first part
of this morning...especially off the coast of southern NJ and
Delaware where a Marine Dense Fog Advisory is in effect until 6 AM.
The fog should diminish by later in the morning as some showers move
over the waters.

It will be quiet on the waters tonight but then expect more rounds
of showers with some storms as well during the day Thursday as the
next low approaches. East winds increase through the day to around
15 gusting 20 to 25 knots by late day. Seas should generally be
around 3 feet through today and Thursday.

Outlook...

Thursday night through Sunday...Overall, mainly sub-SCA conditions
expected through the period but winds and seas may briefly increase
to around 20-25 knots and 4-5 feet, most likely later in the day on
Friday.

&&

.TIDES/COASTAL FLOODING...
Tidal ranges increasing this week with the new moon on Tuesday
evening. Limited onshore flow means that there won`t be much in the
way of serious flooding concerns, but still another round of minor
coastal flooding is probable for Atlantic coastal zones, the
Delaware Bay, and the tidal Delaware River with the high tide cycle
Wednesday night. Another coastal flood advisory will likely be
needed as a result.

Flooding is not expected for our Maryland zones along the
Chesapeake.

&&



$$

SYNOPSIS...MJL
NEAR TERM...Fitzsimmons
SHORT TERM...AKL/Fitzsimmons/MJL
LONG TERM...AKL/Fitzsimmons/MJL
AVIATION...AKL/Fitzsimmons
MARINE...AKL/Fitzsimmons
TIDES/COASTAL FLOODING...AKL