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000
FXUS61 KPHI 201412
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
1012 AM EDT Sat Apr 20 2024

.SYNOPSIS...
A cold front moves offshore this morning. High pressure builds in
from the west this afternoon which will be in place through Tuesday.
A cold front passes by Tuesday night and Wednesday. High pressure
then returns and continues through Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Low pressure lifting well to our north across northern Quebec
is dragging a cold front across our region from west to east,
pushing offshore by midday. That surface front will slow as it
drifts offshore while a new wave of low pressure develops along
it, near Cape Cod, then lifts toward Nova Scotia later today. A
secondary cold front associated with the mid to upper-level
trough axis will pass through this evening, with drier and
cooler air filtering into our region in it`s wake.

Showers increased in coverage earlier this morning, but have
shifted rather quickly to the east of I-95 as the cold front
begins to pass through. Mainly just some leftover isolated
showers will continue to drift off the coast through midday.
Rainfall amounted to only around 0.05 to 0.15 inches for most
areas.

In the wake of the cold front, skies are clearing back across
southeast PA, and that should reach I-95 heading toward midday,
with sunshine breaking out along the coast by mid- afternoon.
This will be a welcome sight for most, as it has been a few days
of fairly cool and cloudy weather. West- northwest winds will
pick up this afternoon, especially from I-95 northwestward, with
some gusts into the 30 mph range. Winds will not be quite as
gusty toward the coast, with less opportunity for clearing,
mixing and momentum transfer there. Highs this afternoon will
reach well into the 60s, except over the Poconos and some of the
nearby ridgetops of NW NJ. Would not rule out 70F in a few
spots from near Philly southward.

With a secondary push of cooler and drier air coming in for
tonight, dewpoints will continue to drop through the 20s, lowest
in areas northwest of the urban corridor. There will be some
high clouds possible, but overall skies will be fairly clear,
and with high pressure building in from the Ohio Valley, we may
see decoupling, easing winds and some rather chilly temperatures
into the 30s by Sunday morning. The growing season is set to
commence across a number of our zones from the Lehigh Valley
across northern NJ on Sunday, and just in time, model guidance
suggests some low to mid-30s possible for lows, coldest toward
Sussex County. Issued a Frost Advisory for Sussex and Warren
counties; that may need to be expanded, but forecast
temperatures in other areas are very marginal for frost, and
high clouds may come in toward morning that would limit frost
formation. Either way, would not rule out patchy frost across
the Lehigh Valley, though that may end up being more of the
rooftop variety rather than a threat to vegetation.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Mostly dry and tranquil weather is expected for the short term
period. The cold front that passes through on Saturday will be
stalled out along the Southeast coast. A weak surface low is
forecast to develop along this boundary and skirt off the Carolina
coast late Sunday. At the same time, large high pressure will be
centered over the Central Plains which will build east through
Monday before shifting overhead Monday night.

The only notable change to the forecast from the previous shift is
that the track of the low has shifted a bit further north on Sunday.
While most of the global and deterministic guidance keeps the low
surpressed to the south...most of the 00Z CAM/hi-res guidance
depicts at least some sprinkles/shower activity reaching into the
Delmarva and extreme southern NJ. As a result, have introduced
slight chance of PoPs (~20%) into these areas for Sunday afternoon.
Elsewhere, skies will remain mostly cloudy. Skies then clear quickly
Sunday night as the low moves into the western Atlantic. Skies will
then remain clear through Monday night. Will have to watch the
development for patchy frost across the Poconos/Lehigh Valley region
both nights.

Highs will be in 50s to around 60 on Sunday, followed by the upper
50s to mid 60s on Monday. Lows generally in the 30s to low 40s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
High pressure begins to shift offshore on Tuesday before completely
vacating the area by Tuesday night. At the same time, low pressure
will be tracking across the northern Great Lakes while moving into
southern Quebec on Wednesday. An associated cold front will be
trailing southward from this low which will pass through the area.
Areawide showers are expected with even a few rumbles of thunder
possible depending on timing and available instability. Best chances
for this would be north and west. Once the front clears the area,
high pressure will quickly build in from the west and remain within
proximity of the area to close out the work week.

Temperatures through the long term period will run close to average
to a few degrees below-normal. Analogs toward the end of the week
and into next weekend, signal that a significant warm-up may be in
store to close out April.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas...

Today...IFR/LIFR ceilings across NJ to near I-95, lifting to
VFR rather quickly from west to east from mid-morning through
midday as skies clear and showers push offshore behind a cold
front. MIV/ACY will be a little slower to improve.
West/northwest winds increasing around 10-20 kt with some spots
seeing gusts near 30 kt during the afternoon hours. Moderate
confidence overall.

Tonight...VFR with mainly clear skies. Winds ease fairly
quickly in the evening, but remaining NW 4-8 kt perhaps through
midnight. High confidence.


Outlook...

Sunday...VFR expected. A slight chance for rain showers near
KMIV/KACY. W-NW winds around 10-15 kt. Moderate confidence.

Sunday night through Tuesday...VFR with mostly clear skies. W-NW
winds on Sunday night into Monday, becoming SE-S winds on Monday
night into Tuesday. High confidence.

Tuesday night into Wednesday...Sub-VFR conditions possible with rain
showers. S winds becoming NW following a cold frontal passage. Low
confidence.

&&

.MARINE...
While some of the buoys offshore still show some near 5 ft seas,
overall conditions are below SCA criteria. Fog has diminished as
well. West to southwest winds will pick up around 10-15 kt
heading into this afternoon. A secondary cold front will swing
winds around to the NNW tonight, with gusts over 20 kt, but
probably not enough for another advisory.


Outlook...

Sunday through Tuesday...No marine headlines expected. Fair weather.
Winds up to 15 kt and seas around 2-3 feet.

Tuesday night through Wednesday...SCA conditions are possible. Rain
showers expected. Winds up to 20-23 kt with seas around 3-4
feet.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Frost Advisory from 2 AM to 8 AM EDT Sunday for NJZ001-007.
DE...None.
MD...None.
MARINE...None.

&&

$$

SYNOPSIS...MPS
NEAR TERM...Dodd
SHORT TERM...DeSilva
LONG TERM...DeSilva
AVIATION...Dodd/DeSilva
MARINE...Dodd/DeSilva