Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
000
FXUS61 KPHI 041916
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
316 PM EDT Mon Jul 4 2022

.SYNOPSIS...
High pressure over the area moves offshore tonight. Several
waves of low pressure will affect the area through the week with
high pressure returning next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Another pleasant day is in progress with seasonable
temperatures in the mid 80s and low dewpoints around 50 degrees.
Surface high pressure centered across the region today will
shift offshore tonight with northwesterly mid-level flow
prevailing through Tuesday. A strengthening surface low will
pass from the Great Lakes toward New England on Tuesday. A quiet
night is expected locally with temperatures falling into the
60s. Cirrus and mid-level cloud cover will increase from
approaching upstream convection across the southern Great Lakes
and Ohio Valley regions. The increasing cloud cover and
increasing low- level moisture advection should limit
radiational cooling to some degree despite initially dry air.

Attention in the near term remains on the potential for severe
thunderstorms in the area during the day on Tuesday. There
remains a good bit of uncertainty on the timing and progression
of the aforementioned remnant convection from upstream across
the southern Great Lakes and Ohio Valley regions. The timing and
track of these remnants will determine if we get any new
convection developing and moving into our area, and if so, the
degree of the intensity and coverage of the storms. The latest
suite of CAM guidance suggests a consensus favoring severe
convection developing in the early afternoon to our west across
the Pennsylvania Capital Region and southwest into central
Maryland and northern Virgina then moving east and impacting the
southern half of the forecast area. This consensus will almost
certainly change in future runs though depending on the
progression of the upstream convection once any complexes begin
to mature.

In any case, if storms do develop and move through our area
during a favorable time in the afternoon to evening, severe
thunderstorms would be probable given the environment in place.
Deep layer effective shear around 40 kts, MLCAPE in the
1,000-2,000 J/kg range, and effective SRH near 200 m2/s2 will be
in play if we have enough time to destabilize. If an initial
round moves through the area early enough in the day, a second
round could be possible later in the afternoon or evening as
well. So long story short, the setup for Tuesday is a low
predictability and low confidence forecast at this juncture.
Confidence will likely increase overnight once we`re within
about 12 hours or so out. Even if we don`t get any new
thunderstorms developing, scattered showers from the remnant
complex(es) from upstream are probable starting by mid to late
morning. Thus, much of the area has high end chance to low end
likely PoPs through much of the day.

The convective uncertainty yields uncertainty in the high
temperature forecast as well, but generally expecting seasonable
values in the mid to upper 80s. The surface low passing to the
north of the area on Tuesday will result in a strengthening
south to southwesterly surface gradient wind. Expecting
sustained winds around 10-15 mph with gusts up to 25 mph.
Outside of any potential storms, skies will be mostly cloudy to
overcast much of the day as well.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
An upper trough with surface low pressure will pass through the
region Tuesday night through Wednesday morning, and this will
drag a cold front through the region Wednesday morning.
Meanwhile, models indicating a potential MCS developing over the
Midwest and passing through the Great Lakes and Ohio Valley
Tuesday night through Wednesday morning. Models seem to keep it
southwest of the region on Wednesday, but there could be another
round of showers and thunderstorms focused on the Delaware
Valley and Delmarva on Wednesday. Wednesday will otherwise be
hot and humid with highs in the 80s to low 90s and surface
dewpoints in the upper 60s to low 70s.

Another wave of low pressure approaches on Thursday. Humidity
levels remain elevated, but temperatures will be several degrees
cooler compared to Wednesday. Scattered showers and
thunderstorms possible.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
High pressure will be established over eastern Canada and the
Northeast, while a frontal boundary will be nearly stationary
over the Mid-Atlantic. That high slides offshore late Thursday
night and Friday morning. Several waves of low pressure will
develop on that boundary as it lifts north as a warm front and
stalls over the area. Several rounds of showers and
thunderstorms will pass through the region Thursday night
through Friday night. Another area of high pressure builds over
the Great Lakes, and that will push the front back to the south.
Depending on how far south that front sags, there may be some
lingering showers into Saturday, but by Sunday, the high will
build to the east, and it looks like the second half of next
weekend and into the start of the new week will be dry.

Temperatures during the period will be a few degrees shy of
normal, topping off in the low to mid 80s.

&&

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

Through 00Z...VFR. Winds around 5 kts or less generally
favoring a west to northwesterly direction. A sea breeze and
bay breeze has developed and already moved past ACY where the
wind should remain southeasterly around 5-10 kts. If the bay
breeze passes MIV, the resulting wind direction will be south to
southwesterly also around 5-10 kts. High confidence.

Tonight...VFR with increasing cirrus and mid-level clouds,
especially after 06Z. Winds will be less than 5 kts and
variable, but generally favoring a southerly direction. High
confidence.

Tuesday...Prevailing VFR conditions are expected with BKN to
OVC mid-level clouds and scattered cumulus. Scattered showers
are expected after 15Z with thunderstorms also possible,
especially near and after 18Z. Thunderstorms could result in
temporary lower restrictions, but confidence is very low on the
timing and coverage of any thunderstorms at this time. Winds
south to southwesterly around 10-15 kts with gusts to around 20
kts possible during the afternoon. High confidence on prevailing
VFR conditions, but low confidence on thunderstorms.

Outlook...

Tuesday night...VFR overall, but sub-VFR conditions in
developing SHRA/TSRA. S winds 5 to 10 kt, becoming SW late.
Moderate confidence.

Wednesday through Wednesday night...Mainly VFR. patchy fog
possible at night. Scattered showers and thunderstorms. NW winds
5 to 10 kt, becoming E Wednesday night. Low confidence.

Thursday through Thursday night...Mainly VFR. Scattered showers
and thunderstorms. E winds 5 to 10 kt. Low confidence.

Friday through Saturday...Mainly VFR. SCattered showers and
thunderstorms. SE winds 5 to 10 kt, becoming LGT/VRB. Low
confidence.

&&

.MARINE...
Conditions will remain below advisory levels along with fair
weather through Tuesday morning. Winds will settle out of the
south by late in the afternoon around 10 kts. Seas 2-3 feet.

Winds and seas will begin to build into Tuesday afternoon as
low pressure passing into New England strengthens the surface
gradient. Expect sustained winds increasing to around 15-20 kts
with gusts up to 30 kts and seas 3-5 feet. Scattered showers are
expected into the afternoon and evening with thunderstorms also
possible. A Small Craft Advisory has been issued for all
coastal waters save for upper Delaware Bay from Tuesday
afternoon through late Tuesday night.

Outlook...

Tuesday night...A SCA may be needed for SW winds 15 to 20 kt
with 25 to 30 kt gusts.

Wednesday through Wednesday night...Sub-SCA conditions.
Scattered showers and thunderstorms.

Thursday through Thursday night...Sub-SCA conditions. Scattered
showers and thunderstorms.

Friday through Saturday...Sub-SCA conditions. Scattered showers
and thunderstorms.

Rip currents...

Light winds and seas today will lead to a low risk for the
formation of dangerous rip currents. Southerly flow and a wind-
driven swell looks notably higher on Tuesday, so included a
moderate risk for the more southeastern facing beaches in New
Jersey... Low elsewhere.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 2 PM Tuesday to 4 AM EDT Wednesday
     for ANZ450>452.
     Small Craft Advisory from 4 PM Tuesday to 4 AM EDT Wednesday
     for ANZ431-453>455.

&&

$$
Synopsis...MPS
Near Term...Staarmann
Short Term...MPS
Long Term...MPS
Aviation...MPS/Staarmann
Marine...MPS/Staarmann


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.