Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 242059

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

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.


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 enahnce 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.


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.


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/23 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

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.


The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY and surrounding areas.

Conditions will vary between MVFR and VFR late this afternoon
and into the early evening hours as moisture continues to wrap
around a coastal low. As the low pulls away through the evening,
all TAF sites are expected to return to VFR and continue for
much of the night. However, we expect MVFR CIGS to return late
in the night and toward daybreak Wednesday as moisture is
expected develop around 2,000-3,000 feet. These lower CIGS are
expected to continue through the morning, before lifting by
midday Wednesday.

Any light rain or drizzle will taper off through the afternoon
and into the evening hours and the rest of the night is expected
to be precipitation free.

Northwest winds will gust 20-25 knots this afternoon and early
evening, before winds could increase to 25-30 knots later this
evening and overnight, although wind gusts may drop off from
time to time overnight. Wind gusts around 20 knots will continue
into Wednesday, before finally diminishing late in the day.

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


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

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

Wednesday 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


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


PA...Winter Weather Advisory until 6 PM EST this evening for PAZ054-
NJ...Winter Weather Advisory until 6 PM EST this evening for NJZ001.
MARINE...Gale Warning until 6 AM EST Wednesday for ANZ431-450>455.
     Small Craft Advisory until 6 AM EST Wednesday for ANZ430.


Near Term...Robertson
Short Term...Robertson
Long Term...Drag
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