Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 131143
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
643 AM EST Fri Jan 13 2017

.SYNOPSIS...
A cold front moving across the area early this morning will push
farther offshore through today. High pressure will build just to our
north tonight, then weaken Saturday into Saturday night as it moves
offshore. An area of low pressure passes to our south Saturday
night, then high pressure will reestablish itself to our north
Sunday, then build offshore Sunday night into Monday. An area of low
pressure is forecast to move into the Great Lakes region Tuesday,
lifting a warm front across the area Monday night into Tuesday
morning. A warm southwest flow will likely develop across the east
coast for the middle to end of the week with a weak cold front
possible Wednesday or Wednesday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
The cold front has started it exit offshore this morning. With
cooler air moving in behind the front, we will see temperatures
start to fall throughout the day, although with the direct
sunlight temperatures may remain fairly steady through the peak
heating of this afternoon. Max temps have already occurred
overnight closer to midnight.

Winds will pick up once the sun rises and we start to mix
efficiently. Winds will become pretty gusty through the afternoon
with gusts around 20 to 30 mph.

&&

.SHORT TERM /SATURDAY/...
High pressure will build into central New York tonight. This will
help to keep us fairly dry and cold as cold air damming sets
up in the northerly flow.

Clouds will start to move back into the region and increase in
coverage as several waves of moisture move into our area. For now,
the precipitation looks to hold off until early Saturday morning.
With temperatures being right near their minimums when the
precipitation starts to move in, we could see more of wintry mix of
snow/sleet/freezing rain at the onset across Delmarva.

A cold night across the region. We went below guidance as it may
take a little while for the thicker cloud cover to arrive and we
should radiate fairly well at the start of the period, especially
across the northern areas and higher elevations. Overnight lows will
drop down into the 20s with teens across the southern Poconos, parts
of the Lehigh Valley and parts of northwest New Jersey.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Several periods of unsettled weather possible through the extended
forecast.

As we move into Saturday, the high to our north is forecast to
weaken and move offshore late in the day and into Saturday night.
As we move through the day, plenty of low-mid level moisture, along
with enhanced vertical lift will spreading across the area as
several short wave/vorticity impulses are forecast to slide
across the area during this time period. This will lead to a
period of precipitation developing and spreading across the area
during the day and into the evening Saturday. The question becomes
what kind of p-type develops across the area. With the weakening
high pressure to our north, we should have cold air get trapped
across the area. The precipitation should start out as snow as the
vertical column should be all below freezing to start. However,
through the day, some warm air aloft could be making its way
across some of the area. This will present a problem for P-Types.
For areas north of the PA Turnpike and I-195 in New Jersey,
precipitation should remain all snow or a mixture of snow and
possibly sleet. However, south of this line things get a little
more tricky. If surface temperatures have a hard time rising
during the day, this could lead to a period of a wintry mix of
snow/sleet/freezing rain. We have decided to not issue an advisory
yet as there is still some uncertainty in where the freezing rain
will develop.

The moisture and enhanced lift should push south of the area
overnight Saturday and precipitation should come to an end during the
overnight hours.

High pressure will reestablish itself Sunday and move just to our
north during the day before moving offshore overnight. Drier air is
expected to move across the area which should keep the forecast dry.
There is an area of moisture and lift that is forecast to pass to
our south, but should remain just south of the area.

By Monday, the high builds offshore to our north and return flow
develops across the area which will allow for some warming across
the area. A warm front is forecast to lift across the area overnight
Monday and move to our north Tuesday as an area of low pressure
moves into the Great Lakes. Several short wave/vorticity impulses
will continue to move across the area in the westerly flow aloft.
This will keep the chance for precipitation to develop as the warm
front lifts across the area and passes to our north. There is the
potential for a wintry mix of snow/sleet/freezing rain for areas
along and north of I-78 Monday night into Tuesday morning. South of
this area, the precipitation may be mostly rain, or a mix of
rain, sleet, and snow with surface temperatures above freezing.

The warm front lifts north of the area by Tuesday. A warm southwest
flow then develops through Tuesday and Wednesday across the area.
Several short wave/vorticity impulses will continue to move across
the area, which will lead to a chance of precipitation. Temperatures
are forecast to be above freezing, so any precipitation should be all
rain.

A weakening cold front is forecast to move across the area during
the middle of the week. However, the there is timing differences
with the GFS being about 12 hours faster than the ECMWF.
Nevertheless, a chance of precipitation will continue through
Thursday, and with warm temperatures, any precip is expected to be
all rain.

&&

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

Expect VFR conditions to continue with breezy northwest winds 10
to 20 knots with gusts up to 25 knots. Winds will gradually
diminish later this afternoon and then we should lose the
gustiness entirely by early evening. Ceilings are expected to
lower towards the end of the TAF period as the next system
arrives. Light precipitation may arrive towards the tail end of
the TAF period, mainly at KILG and KMIV.

OUTLOOK...

Saturday-Saturday night...Deteriorating conditions with MVFR or IFR
conditions developing Saturday and continuing into Saturday night.
Wintry mixture of precipitation possible, with mainly snow/sleet for
ABE/RDG/TTN, and snow/sleet/freezing rain possible for the remainder
of the TAF sites.

Sunday-Sunday night...Conditions improving to VFR.

Monday-Tuesday...Generally VFR early, lowering to MVFR, then to IFR
late Monday night into Tuesday. Chance of precipitation late Monday
into Tuesday. A wintry mix possible, mainly north of TAF sites Monday
night into early Tuesday

&&

.MARINE...
The Small Craft Advisory remains up on the ocean waters through 6pm
tonight. Winds will gust out of the northwest through the early
evening as decent cold air advection arrives and drags the colder
air over the warmer waters. Seas are still running around 5 to 7
feet but will start to drop through this afternoon.

Both seas and winds are expected to fall below Small Craft Advisory
criteria by early this evening. Both may fall below criteria by late
afternoon and the advisory may be able to be cancelled a bit
early.

OUTLOOK...

Saturday-Tuesday..Sub-Small Craft Advisory conditions expected
through the period, although winds may gust 15-20 knots at times
Saturday night/Sunday.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ450>455.

&&

$$
Synopsis...Robertson
Near Term...Meola
Short Term...Meola
Long Term...Robertson
Aviation...Robertson/Meola
Marine...Robertson/Meola



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