807
FXUS61 KPHI 080146
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
946 PM EDT Tue May 7 2024

.SYNOPSIS...
An area of low pressure tracks by to our north late tonight and
early Wednesday 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 WEDNESDAY/...
As of 935 PM, the last of the showers have dissipated with the loss
of daytime heating. Mostly just some bands of mid to high level
cloudiness streaming across our area. Some stratus and/or fog was
along and off the Delaware Beaches at sunset, and some of this
should expand northward and inland some late tonight as moisture is
on the increase from the south and southwest. Slowed the PoP
increase some from west to east overnight, as most of the guidance
including the recent runs of the HRRR have the bulk of the
showers/thunder closer to daybreak. Adjusted the hourly temperature,
dew point, wind and sky grids to account for the latest observations
and trends.

Otherwise, low pressure pivots around the Great Lakes. As the
associated warm front reaches the area, showers will commence. The
heaviest and most widespread will be north of Philadelphia. A few
thunderstorms are possible late as some instability is forecast to
advect eastward late tonight in response to strengthening flow and
low-level warm air advection. Rainfall amounts up to a third of an
inch are anticipated. Overnight lows will be in the 50s to lower 60s.

For Wednesday, the showers (and maybe a thunderstorm) associated
with the warm front will be moving out in the morning. For most of
us, it will be the first part of the morning. Clouds will diminish
in the afternoon allowing temperatures to rise quite a bit.
Wednesday`s 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.

There could be some isolated afternoon showers/storms developing,
however the forcing for ascent is weak and this should limit the
coverage. The model forecast soundings do show a well mixed boundary
layer developing in the afternoon (inverted-V signature), and this
could result in an isolated gusty thunderstorm.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
A fairly busy/active weather pattern persists across the area
through the short term period.

For Wednesday night, one low pressure system moves out to sea as it
passes east of New England with a new low starting to move into the
midwestern states. This will eventually push a warm front towards
the area by Thursday morning which could start to bring in some
showers/storms towards sunrise across eastern PA and Delmarva.

Thursday is shaping up to be more unsettled as this next area of low
pressure referenced above moves across the region bringing more
widespread showers and storms. That said, there is still a lot of
uncertainty on the track of this system which will have implications
both on the high temperatures and the severe weather threat. Model
consensus maintains a low tracking eastward near Delmarva which
would limit how far north the warm front gets. Deep layer shear will
be quite strong meaning anywhere near and south of the warm front
will have a heightened severe weather threat Thursday afternoon into
the evening but right now the most favored area looks to be over
Delmarva and southern NJ. The Storm Prediction Center has a Marginal
and Slight Risk for severe weather across this region. This could
change, however, if the system and its warm front tracks farther
north. Currently expect highs Thursday ranging from the upper
60s/low 70s north to the mid/upper 70s south but again, this is
contingent on the track of the low. With an overall slower trend
with the system, showers/storms could last through a good portion of
Thursday night although any severe weather threat should diminish
through the nighttime hours with the loss of daytime heating.

On Friday surface, 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 70 percent north), under generally overcast skies. It will
also be cooler with highs mostly in the upper 50s to mid/upper
60s.

&&

.LONG TERM /FRIDAY NIGHT 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 by Sunday as the next shortwave trough swings through (POPs
40 to 60 percent) and there will also be more in the way of cloud
cover.

Finally by early next week it should start to trend warmer and drier
as the upper trough moves out and the flow over the east becomes
more zonal.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas...

Tonight...VFR conditions lower to MVFR/IFR overnight as areas of low
clouds and patchy fog develop. Some showers expected after 06z.
Southerly winds 4-8 knots becoming light and variable to locally
calm. Low confidence in the timing and extent of the sub-VFR
conditions.

Wednesday...MVFR/IFR conditions in the morning as showers end, then
improving to VFR. An isolated shower or thunderstorm possible in the
afternoon. Southwest to west winds increasing to 10-15 knots with
gusts to around 20 knots. Low confidence on how fast conditions
improve in the morning.

Outlook...

Wednesday 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. More widespread SHRA with
scattered TSRA Thursday afternoon and evening.

&&

.MARINE...
Tonight and Wednesday...Sub-SCA conditions. Some fog develops
tonight before dissipating Wednesday morning.

Outlook...

Overall, sub-SCA conditions through the period. Scattered showers
and thunderstorms will result in locally higher wind gusts and seas,
with biggest impacts coming on Thursday afternoon and evening.

&&

.TIDES/COASTAL FLOODING...
Tidal ranges increasing this week as the new moon arrives this
evening. Limited onshore flow means that there won`t be much in
the way of serious flooding concerns, but still widespread
minor tidal flooding is expected with the high tide this evening
for Atlantic coastal zones, the Delaware Bay, and the tidal Delaware
River. A Coastal Flood Advisory remains in effect for these areas.
Another round of minor coastal flooding is probable for these areas
with the high tide cycle Wednesday night.

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

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Coastal Flood Advisory from midnight tonight to 5 AM EDT
     Wednesday for PAZ070-071-104-106.
NJ...Coastal Flood Advisory to 2 AM EDT Wednesday for NJZ016.
     Coastal Flood Advisory to 1 AM EDT Wednesday for NJZ012>014-020>027.
     Coastal Flood Advisory from midnight tonight to 5 AM EDT
     Wednesday for NJZ017>019.
DE...Coastal Flood Advisory to 2 AM EDT Wednesday for DEZ001.
     Coastal Flood Advisory to 1 AM EDT Wednesday for DEZ002>004.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...MJL
NEAR TERM...Gorse/Kruzdlo
SHORT TERM...Fitzsimmons/MJL
LONG TERM...Fitzsimmons/MJL
AVIATION...Gorse/Kruzdlo/MJL
MARINE...Kruzdlo/MJL
TIDES/COASTAL FLOODING...PHI