Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 242259
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
559 PM EST Tue Jan 24 2017

.SYNOPSIS...
The coastal low will move east of Cape Cod this evening. High
pressure builds over our region on Wednesday. A cold front passes
southeastward off the mid Atlantic coast Thursday followed by a
second cold front moving through our region late in the weekend.
Another frontal system approaches early next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
555 PM Update...The Winter Weather Advisory for the southern
Poconos and Sussex County, NJ is being allowed to expire at 6
PM. Some mainly light snow/sleet will linger for awhile longer
there, however many places are still above freezing and any
amounts are expected to be very light. A few bands of mainly
light rain continue to wrap around a deep surface low to our
east, and the Correlation Coefficient data (CC) from the KDIX
radar indicates mixed phases in some of the bands. This indicates
some sleet, and some sleet has been reported under the main
band from Warren to Ocean counties. This appears to be weakening
some now.

Otherwise, low pressure south of Long Island, New York will
continue to drift northeast and make its way into the Gulf of
Maine overnight tonight. A steady northwest flow will continue
across the area through the overnight hours. Winds will gust
20-25 mph at times through this evening, but winds could
increase to 25-30 mph at times overnight. For some places, wind
gusts may drop off from time to time.

The mid level low remains offshore this evening and is helping
to enhance lift across the eastern half of the area. Light to
at times moderate rainfall will continue through late this
afternoon and early evening for portions of northern and east
central New Jersey where the greatest moisture/lift combination
is located. As the surface low continues to drift eastward, the
rainfall will taper off into this evening.

We have kept the Winter Weather Advisory in place for
Carbon/Monroe, Pennsylvania and Sussex, New Jersey. There
continues to be a few places, mainly in the higher elevations,
where temperatures are around freezing, or could fall below
freezing through sunset. With the light rain or drizzle moving
across the area, some light freezing rain or drizzle is possible
until the precipitation tapers off this evening. There may also
be some sleet or snow mixes in for the higher elevations,
although it is expected to be little to no accumulation.

Temperatures tonight are forecast to drop around or below
freezing for many areas. So even after the precipitation ends,
any left over moisture on untreated surface may refreeze.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
On Wednesday, our area will be on the far northern fringe of
high pressure centered across the Bahamas, while low pressure
moves into the Canadian maritimes. Northwest flow will continue
across the area through the day, with the strongest winds
expected for the first half of the day. Winds could continue to
gust 20-25 mph early in the day, before gusts diminish later in
the afternoon. Some cloud cover can be expected early in the
day, especially for the western half of the area, before the
clouds begin to break and clearing skies develop for the second
half of the day. Temperatures should warm quite nicely with
everyone expected to be above normal.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
500 MB: Weak ridging Wednesday night will be followed by several
short waves that develop the mean of a positive trough in the
eastern USA that may strengthen to 3 sd below normal in the
central Appalachians late Sunday.

Temperatures: calendar day averages about 13-14 degrees above normal
Thursday, 7 to 8 degrees above normal Friday, maybe around 2 degrees
above daily, this Saturday through Tuesday.

Forecast basis: Unless otherwise noted, a 50 50 blend of the 12z/24
GFS/NAM MOS guidance Wednesday night-Thursday night, thereafter the
12z/24 GFS MEXMOS Friday, and then the 15z/24 WPC guidance
Friday night - Tuesday, at times blended with the 12z/24 GFS
MEXMOS guidance or the long term temps were adjusted because of
the 12z/24 ECMWF 18z 2m temperatures.

The dailies...

Wednesday night...waa showers likely for at least portions of the
area late at night and pops have been raised for sct event. The
dry EC held me back ydy but now the UK and Canadian are onto
it. Pending further review no ice hazard needed, though we are
keeping in mind the new 1-3" sleet snow acc north of I-80 that
will be very slow to melt. Early radiational cooling might allow
some spotty freezing rain north of I-80. For now, not forecast.
Confidence: average

Thursday...leftover morning showers, mainly southeast of I95.
Then caa and breezy during the afternoon with partial clearing.
Confidence: above average

We have a little snow grid for Thu night. (Poconos sct snow
showers).

Friday-Sunday...partly cloudy. northwest flow pattern. maybe
some caa flurries in the Poconos at times, especially late Thu
night or Friday. Breezy during the afternoons. Increasingly
cold.  Confidence: above average

Monday...Still uncertainty regarding the development of some
snow (12z/24 operational EC doesn`t have the same pattern as
the GEFS) since a pretty strong trough may be forming in the
lower Ohio valley late Sunday. Dont yet count out a light snow
event for parts of the area (especially Delmarva) but the fcst
for now is dry. Confidence: below average.

Tuesday... Another frontal system may be approaching late in the
day and followed WPC guidance.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Tonight...Ceilings varying between MVFR/VFR for awhile this evening,
then all areas are expected to be VFR overnight. A few bands of
mainly light rain continue to move from northwest to southeast, and
these are expected to weaken through the evening. There is a chance
that some MVFR ceilings redevelop after about 08z, however
confidence is low at this time. Northwest winds near 15 knots with
gusts to about 25 knots at times.

Wednesday...Some areas of MVFR ceilings possible to start, otherwise
VFR with less cloud cover through the day. Northwest winds 10-15
knots with some gusts up to 20 knots, diminishing toward late
afternoon.

OUTLOOK...
Wednesday night and Thursday morning...VFR though a period of
showers may very briefly lower conditions to MVFR after 06z/26.
Confidence: average.

Thursday afternoon...VFR with gusty westerly winds behind a
cold front to 25 or 30 kt.  Confidence: above average

Friday, Saturday and Sunday...Mostly VFR conditions expected.
Westerly winds gust each afternoon 20-30 kt. Confidence: above
average.

&&

.MARINE...
The Gale Warning for the Atlantic Coastal waters and lower
Delaware Bay has been extended until 6 am Wednesday. While winds
are currently below gale force this afternoon, winds are
expected to increase this evening and overnight to 35-40 knots.
For upper Delaware Bay, winds are expected to remain 25-30
knots.

Winds will diminish to Small Craft Advisory levels Wednesday
morning, then fall below advisory levels later in the day.

OUTLOOK...
Wednesday night...no headlines. sw wind. Confidence: average


Thursday through Friday...West wind gusts 25-30 KT and seas build
above 5 feet with sca conditions likely, especially Atlantic
waters.  Confidence: above average


Saturday and Sunday...West wind gusts near 25 knots possible.
Confidence: above average

&&

.CLIMATE...
Philadelphia continues to project a January average of at least
38 degrees, 5 degrees or more above normal. This should be at
least the 17th warmest January in the period of record back to
1874.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Gale Warning until 6 AM EST Wednesday for ANZ431-450>455.
     Small Craft Advisory until 6 AM EST Wednesday for ANZ430.

&&

$$
Synopsis...Drag
Near Term...Gorse/Robertson
Short Term...Robertson
Long Term...Drag
Aviation...Drag/Gorse
Marine...Drag/Robertson
Climate...



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