Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 122101
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
401 PM EST Mon Nov 12 2018

.SYNOPSIS...
Low pressure developing over the Southeast will continue to move
northeast, traversing our area through the overnight. High pressure
will slowly build into the region through Wednesday night, before
moving off to the northeast. Another area of low pressure will then
gather strength over the southeast and move northward along the
coast Thursday afternoon into Friday morning in a similar manner to
tonight`s low. High pressure should build toward our south into the
upcoming weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Cool conditions and increasing clouds continue late this afternoon
and into the early evening hours as high pressure continues to move
eastward offshore of the northeast coast. Meanwhile, a stationary
frontal boundary/surface trough located along the east coast from
North Carolina southward will expand northward this evening and
overnight, while an area of low pressure develops along this
boundary. This low will track northward during the overnight hours
and through daybreak Tuesday. Meanwhile, a cold front will be
advancing toward the area from the west.

North of the low, and ahead of the cold front, plenty of moisture
and lift will advect across the area as several short wave/vorticity
impulses move across the area. This will lead to an increase in
coverage of precipitation through this evening and overnight.
Temperatures across the higher elevations of northeast Pennsylvania
and northern New Jersey will be cold enough for some snow and/or
sleet to occur at the onset of the precipitation. However, as warm
air continues to move northward, all precipitation is expected to
change to rain overnight. Therefore, little accumulation is
expected, generally an inch or less.

Overall QPF amounts are forecast to be between 0.75-1.00 inches, with
the highest across southern New Jersey, Delaware, and Maryland where
there is the potential for up to 1.5-2.0 inches. Rainfall rates are
not expected to be significant, however, there is the possibility if
rates reach up to 1 inch per hour, some urbanized/poor drainage
flooding may occur. There is a limited amount instability forecast,
and is confined to southern Maryland, southern Delaware, and
southern New Jersey, so we will have a slight chance of
thunderstorms there.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
The coastal low will continue to quickly lift northward along the
Delaware and New Jersey coasts through the morning hours. There will
be ongoing showers across the are for a couple of hours around and
shortly after daybreak Tuesday. However, as the low lifts
northeastward, the showers will taper off from west to east. The
exception to this is that another band of showers may develop during
the afternoon for southern Maryland, southern Delaware, and
southeastern New Jersey as a couple of more short waves move across
the area.

With the low moving to our northeast through the day, the pressure
gradient will tighten across the area, leading to gusty winds.
Northwest wind gusts of 20-30 mph are expected across the area.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Summary: Wednesday will feature dry weather and mostly clear skies.
Another low pressure system will move up from the south late
Thursday into Friday bringing more extensive precipitation to the
region. Confidence for wintery weather has increased somewhat with
this forecast package. Isolated rain/snow showers or
sprinkles/flurries will be possible over the weekend, especially
toward the northern portion of the area. Otherwise, a cold and dry
weekend looks to be in order with high pressure centered across the
Southeast. High pressure and dry weather persists into early next
week.

Tuesday night through Wednesday night...Upper trough moves out as
westerly flow sets up across the region. A few lingering showers may
stick around across far south NJ and southern Delmarva through the
early evening hours. High pressure will build in from the west with
dry and mostly clear conditions expected through Wednesday night.
Wednesday will be seasonably cold with high temperatures struggling
to climb above 40 degrees. Lows Wednesday night will once again fall
into the 20s for most locations across the area.

Thursday through Friday...A cut-off upper low positioned across the
ArkLaTex region Wednesday will get picked up and ejected
northeastward across the Ohio Valley by another upper trough digging
southward through Friday. This will result in another area of low
pressure developing and moving up the East Coast late Thursday
through Friday. With the colder air that will be in place in the
wake of the early week system and high pressure anchored initially
across New England, wintery mix (rain mixing with snow/sleet) is
looking more likely at the onset of this event, particularly our
northern-most zones and higher elevations where precip may remain a
mix of rain/snow or all snow through the majority of the event. The
onset mixed precip type may easily be experienced across even our
southern most zones. The latest ECMWF and GFS have trended faster
with precip onset time (as early as daybreak Thursday), meaning less
time to warmup with daytime heating or advection before precip
overrunning begins. The faster the system is, the more widespread
mixed precip will result. This will also depend on the exact track
of the low, which is still uncertain. All that said, temperatures
are expected to be too warm in most area for any significant or
measurable accumulations. The Poconos may have some light
accumulations, however, if temps remain cold enough. Even after
precip begins, temperatures will warm throughout the day into the
upper 30s and 40s except the Poconos where temps are more likely to
remain closer to the freezing mark. Expecting about 1-1.5 inches of
rainfall with this system as of now. Rain will come to an end by
late Friday morning with a few showers lingering through the
afternoon hours.

Friday night through Monday...High pressure will begin building from
the west through the weekend with northwesterly flow ushering in
cooler air. A few light rain/snow showers or sprinkles/flurries will
be possible late Saturday and Saturday night. Temperatures are
expected to remain below normal into early next week with highs in
the 40s and lows in the 20s and 30s for most. Sunday and Monday look
quiet under mostly clear skies.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.

Tonight...VFR this evening, lowering to MVFR then IFR later this
evening and overnight as rain increases across the area. South-
southeast winds around 5 knots, become light and variable or shift
toward the east-northeast around 5 knots later this evening and
overnight.

Tuesday...Light rain begins to taper off during the morning hours.
conditions will improve from IFR to MVFR as rain tapers off, and may
return to VFR during the afternoon. Wind shift to the north-
northwest during the morning and into the afternoon, and increase to
10-15 knots, with gusts 20-25 knots possible.

OUTLOOK...
Wednesday and Wednesday night...generally VFR with high clouds
moving into the area. High confidence. Winds 10-15 knots with gusts
to 20 knots inland and 25 knots along the coast.

Thursday through Friday...VFR turning MVFR with rain showers moving
into the area from southwest to northeast. Some mixed precipitation
is possible early Thursday, though little to no accumulation
expected. Remaining rain showers move off to the north Friday
afternoon, though some lingering drizzle and showers will be
possible through the evening. Lowest visibilities over the higher
elevation of the Poconos and NW NJ. Low confidence. Winds 10-15
knots with gusts to 20 knots inland, 25 knots along the coast.

Friday night through Sunday...generally VFR, though some snow
showers with temporary reductions to MVFR possible over the Poconos
Saturday and Sunday, though confidence is not particularly high on
the timing of these. Winds 5-10 knots with gusts possibly reaching
15-20 knots, mostly along the coast.

&&

.MARINE...
Small Craft Advisory is in effect starting later tonight and
continuing through the day Tuesday. Winds are expected to increase
out of the east to northeast overnight ahead of an approaching low
pressure system. Strong winds will continue during the day Tuesday
as the low lifts to our northeast and gust 25-30 knots.

OUTLOOK...
Wednesday...lingering SCA conditions possible with SCA ending at 6
am. A few gusts to 30 knots possible through the early afternoon
before tapering off into the evening. Fair weather expected. Seas 3-
6 feet.

Thursday through Friday...sub-SCA conditions initially with wind
gusts picking up and approaching 30 knots over the open waters
Thursday night. Seas building to 6-12 feet into the afternoon
Thursday, lingering into Friday.

Friday night through Sunday... SCA conditions possible Friday night
with gusts 25-30 knots, diminishing to sub-SCA over Saturday. Seas 5-
10 feet relaxing to 4-6 feet into the day Saturday, then 2-4 feet
Saturday night.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory from 1 AM Tuesday to 6 AM EST Wednesday
     for ANZ430-431-450>455.

&&

$$
Synopsis...Davis
Near Term...Robertson
Short Term...Robertson
Long Term...Davis/Staarmann
Aviation...Davis/Robertson
Marine...Davis/Robertson


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