977
FXUS61 KPHI 181056
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
656 AM EDT Sun Aug 18 2024

.SYNOPSIS...
A warm front will lift north through the area this morning
ahead of a cold front that will approach the area later tonight.
The cold front will gradually work its way through the area
late on Monday into Monday night with a secondary front passing
through on Tuesday. In its wake, high pressure builds into the
region and remains in control through the end of the week and
into next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
655 AM update...Nudged POPs downward a bit to account for the
lull being more pronounced this morning. No other changes at
this time.

3 AM discussion...
Warm front is slowly lifting northward across the region early
this morning and will clear the area by later this morning.
Aloft, one modest shortwave acting on the very moist air moving
northward has produced showers and thunderstorms, but these
likely clear most of the region toward or shortly after dawn. We
expect a bit of a lull in the morning, though a few scattered
showers could still be around. Then, the afternoon looks quite
stormy as a slightly more potent shortwave moves in during peak
heating with a very moist and increasingly unstable atmosphere
now in place. Thus, the stage is set for both flooding rain
(with high PW`s, high rain rates and some localized training
will be possible) and severe weather (mainly damaging winds,
though possibly a stray tornado or a little hail). Main time
frame for the area is afternoon into early evening, with what
would normally be rush hour currently looking like prime time.
With latest CAMS indicating a stronger signal for localized
heavy rain to the north, have included remaining northern
counties in the flood watch. SPC has also widened their slight
risk zone to include most of our region.

Things quite down gradually overnight, but there isn`t a
significant front moving in just yet to clear out the moisture,
so low clouds and patchy mist/fog could develop overnight.
After a day with highs in the low-mid 80s (except 70s
shore/Poconos), lows tonight will drop into the upper 60s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
For Monday, the initial cold front will cross through the area
during the afternoon before moving offshore by Monday evening.
During the day, skies should partially clear leading to some
breaks of sun especially over the Coastal Plain as there will
likely be a lull in activity from the night prior. With
temperatures warming back into the low to mid 80s and dew points
remaining in the low to mid 70s, this should allow instability
to increase during the afternoon. Effective bulk shear will be
around 30 kt or so with lapse rates approaching 7 C/km.
Considering the environment, especially in areas that encounter
some clearing during the day, there will likely be another round
of convection to occur during the afternoon associated with the
actual cold front. As a result, the Storm Prediction Center has
outlooked a Marginal Risk (Level 1/5) for severe weather from
Philadelphia southward. The primary threat will be damaging wind
gusts with any organized convection along with localized flash
flooding possible. However, this ultimately may depend on how
much clearing actually occurs because if more clouds hang
around, then the greater instability may not be tapped into. The
cold front will cross through the area on Monday night, leaving
just some residual showers overnight.

For Tuesday, the biggest change to the forecast from the
previous update is that Tuesday now looks mainly dry. Following
the initial frontal passage the night before, sufficient drying
should occur as our dew points fall back into the 50s.
Temperatures will be noticeably cooler as well with highs only
in the mid 70s -- a taste of fall is certainly on the way. A
secondary front will then pass through later Tuesday causing
another push of drier air to surge in from the north and west,
resulting in dew points falling down into the 40s by Tuesday
night. The combination of clear skies and light winds will
result in an efficient night for radiational cooling, so low
temps are forecast to be mainly in the 50s with even some upper
40s into the Poconos!

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Following the passage of the secondary front, high pressure
will build in from the west on Wednesday. The high will center
itself near the area on Thursday and Friday before shifting to
our south into next weekend. Aloft, the area will be situated
under the base of a deep upper trough with a cut-off low
centered over interior New England through Thursday. By Friday,
the axis of the trough departs, as rising upper heights begin to
move back toward the region.

All in all, tranquil, dry and seasonably cool weather will be
in place for Wednesday and Thursday. Dry weather conditions will
continue into Friday and Saturday as temperatures return closer
to normal to potentially slightly above normal into next
weekend. Enjoy!

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Today...Conditions start out mix of VFR/MFR/IVFR and should
lift to VFR at most, if not all terminals as model guidance
continues to indicate a lull in showers and thunderstorms for
the morning- midday time period. Widespread afternoon showers
and thunderstorms expected to continue into the night that will
bring IFR conditions at times. Winds out of the southeast around
5-10 kt with gusts up to 20 kt possible at KACY. Higher gusts
possible in convection as well. Moderate confidence in timing of
conditions lifting to VFR. Low confidence in where bulk of
showers/thunderstorms set up.

Tonight...Restrictions possible for the night as some
showers/thunderstorms linger with patchy fog developing as well.
Southeast winds around 5 kt. Low confidence overall.

Outlook...

Monday through Monday night...Mainly VFR expected with areas of
sub- VFR possible during the afternoon and evening. Showers and
thunderstorms likely especially in the afternoon.

Tuesday through Thursday...VFR. No significant weather
expected.

&&

.MARINE...
Small Craft Advisory in effect for the ocean as seas build to 5
to 7 feet due to larger swells from distant Hurricane Ernesto.
Sub-SCA conditions expected for Delaware Bay. VSBY restrictions
in showers and thunderstorms beginning this morning and through
tonight. Locally gusty winds possible with thunderstorms.

Outlook...

Monday through Monday night...A Small Craft Advisory remains in
effect for all Atlantic coastal waters due to seas around 5-7
feet. No marine headlines are expected on the Delaware Bay.

Tuesday...SCA conditions possible early in the morning due to
lingering seas above 5 feet. Otherwise, seas should abate
through the day on Tuesday with no additional marine headlines
expected.

Tuesday night through Thursday...No marine headlines expected.
Fair weather.

Rip Currents...

Large swells associated with Tropical Storm Ernesto will
continue to propagate toward our region through the remainder of
the weekend and potentially into the early portion of the week.

For Today...South-southeast winds around 10-20 mph. Breaking
waves between 4-6 feet possible with a 11 to 13 second period.
As a result, have maintained a HIGH risk for dangerous rip
currents for both the Jersey Shore and Delaware Beaches.

For Monday...South-southwest winds around 10-15 mph. Breaking
waves between 3-6 feet possible with a 11 to 13 second period.
With the upcoming full moon and low tide occurring in the
afternoon, have maintained the HIGH risk for rip currents for
the Jersey Shore. With the wind becoming a bit more offshore
and lower wave heights expected off the Delaware coastline,
have maintained a MODERATE risk for dangerous rip currents for
the Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

&&

.TIDES/COASTAL FLOODING...
Widespread minor coastal flooding is expected to occur through
at least the Monday night high tide cycle as an approaching
Full Moon, combined with steady south/southeasterly flow, and
swells from passing Tropical Storm Ernesto impact tidal
communities.

Tonight`s high tide will bring widespread minor tidal flooding
with a Coastal Flood Advisory in effect for all tidal zones with
the exception of the Chesapeake. Guidance has been underdoing
high tide levels, as it usually does with passing tropical
systems, and have had to nudge up the forecast slightly.
Regardless, some inundation of low lying areas is likely
tonight and possibly Monday night. Still not expecting flooding
to reach moderate levels at this time.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through late tonight for PAZ054-055-060>062-070-
     071-101>106.
     Coastal Flood Advisory until 5 AM EDT Monday for PAZ070-071-
     106.
NJ...Coastal Flood Advisory until 1 AM EDT Monday for NJZ016.
     Flood Watch through late tonight for NJZ001-007>010-012-013-
     015>019.
     Coastal Flood Advisory until midnight EDT tonight for NJZ021.
     Coastal Flood Advisory from 6 PM this evening to midnight EDT
     tonight for NJZ012>014-020-022>027.
     High Risk for Rip Currents through Monday evening for NJZ014-
     024>026.
     Coastal Flood Advisory until 5 AM EDT Monday for NJZ017>019.
DE...Coastal Flood Advisory until 1 AM EDT Monday for DEZ001.
     Flood Watch through late tonight for DEZ001.
     Coastal Flood Advisory until midnight EDT tonight for DEZ002.
     Coastal Flood Advisory from 6 PM this evening to midnight EDT
     tonight for DEZ003-004.
     High Risk for Rip Currents through this evening for DEZ004.
MD...None.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for ANZ450>455.

&&

$$

SYNOPSIS...DeSilva/RCM/Robertson
NEAR TERM...Hoeflich/MJL/RCM
SHORT TERM...DeSilva
LONG TERM...DeSilva/Robertson
AVIATION...DeSilva/Hoeflich/MJL/RCM/Robertson
MARINE...DeSilva/Hoeflich/MJL/RCM/Robertson
TIDES/COASTAL FLOODING...PHI