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FXUS61 KPHI 090218

Area Forecast Discussion
National Weather Service Mount Holly NJ
918 PM EST Thu Dec 8 2016

An area of low pressure will continue to slowly drift across eastern
Canada through Friday, and offshore by Saturday.  With high
pressure to our west, strong west to northwest flow will remain
through Saturday. A warm front is expected to lift across the area
Sunday night, before an area of low pressure moves north of the
region around Monday. This system will pull a cold front across
the area Monday, then another quick moving frontal boundary may
move across the area around Tuesday night.



Note: tonight's low temp fcst at PHL will be the coldest of the
season so far at PHL and remember last winter, it didn't drop
into the 20s until January 4th 2016!

Tonight...A light west-northwest breeze except PHL may gust 18-20
kt all night as well as adjacent all bodies of water as boundary
layer temps show increasing land-sst differential and resultant
enhanced land breeze effect, near the water. Clouds across
southern New Jersey and Delaware are likely to slowly erode over
the next few hours. Radiational cooling slightly delayed in those

Exception to the mostly clear skies: near the Poconos where lake
effect clouds arrive and then flurries should eventually develop
there sometime tonight.

Fcst was a 50 50 blend of the 12z GFS/NAM mos guidance.


Cold air advection and lake effect streamers of moisture, flurries
and snow showers from the Great Lakes combined with the cold
trough aloft increase the snow squall probabilities tomorrow and
so at least sct flurries to near I-95 (not expecting flurries or
sprinkles along the coast) and suspect small accumulation in
parts of Poconos Friday afternoon. A snow map will post shortly
followed by snow probs around 5PM for this first little terrain
related accumulation event.

Otherwise...mostly sunny skies to start (mo cloudy Poconos) becomes
considerable cloudiness everywhere during the afternoon. Breezy
with west northwest wind gusts 25 to possibly 30 mph.

Forecast basis was a 50 50 blend of the 12z gfs/nam MOS and added
a degree to the max T per the 12z/8 EC 2m temps.


Strong nwly flow will continue Fri night into Saturday a large
area of high pres builds to the w and a departing low moves away
to the e. This will keep things relatively dry but cold and
breezy. There could be a passing flurry or snow shower but that
should be the extent of any precip.

The high then moves over us Sat night and the wind will decrease.
We should be in for a cold night, before the high moves ewd.

As the high moves away, low pres will take shape over the plains
and head toward the Oh vly on Sun and drag a wmfnt thru the
region Sun night. Precip will begin acrs the area later Sun into
Sun night. There are still some disagreements in the mdls as to
the timing and path of the low, which will ultimately impact what
type of precip falls and where. However, it does appear that the
bulk of the precip will fall Sunday night into early Monday.
Temps will be cold enough Sunday night n and w for pretty much all
snow and a plowable event which would impact the Monday mrng
commute. Further s, there may be some low accumulations before a
changeover to rain on Monday. Acrs srn and ern areas, we shud
expect mainly rain.

The cdfnt assocd with the low will move thru on Mon and end the
precip. Then, dry wx is expected for later Mon into Tue.

Then, twd the end of the pd, there is the potential for another
mixed precip event. The GFS is faster bringing this sys in as
early as Wednesday morning, while the ECMWF holds off until later
Wed. Again, temps will be warm enough s and e for mainly rain,
while n and w it would likely be wintry precip. Again, the timing
and track of the sys will determine ultimately who gets what and
it is a week away but clearly we are entering a more active wx


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

Tonight: VFR, high scattered deck eroding for the southern
terminals of KMIV and KACY. West-northwest winds around 10 knots
with a few higher gusts. A mid VFR deck will likely encroach
toward KABE and KRDG, will look into inclusion with 06Z TAFS at
these sites.

Friday...Generally VFR sct-bkn aoa 4000 ft, although CIGS may
briefly lower to MVFR in scattered snow showers e PA higher terrain.
An afternoon flurry or sprinkle is possible southeastward to ILG-
PHL-TTN. Gusty west to northwest winds 22-30 knots.


Fri night - Sat...Generally VFR, although cigs may occasionally
lower to MVFR. Scattered showers or flurries/sprinkles are
possible during the daytime of each day which may temporarily
lower conditions. Gusty w to nw wind 15-25 kts. High confidence.

Sun...VFR early, possibly lowering to MVFR by the afternoon. Rain
or snow psbl late in the day. Moderate confidence.

Sun night-Mon...Conds lower to MVFR then IFR. RA and SN becoming
likely, best chc for SN n. Most of DE and MD will stay all rain.
Any SN over srn NJ and sern PA will change to RA durg Mon.
Accumulating snow over nrn and wrn areas.  Mdt confidence.


Based on the latest data is it looking more questionable that we
will see gale gusts. Soundings from the HRRR and RAP show the
potential for the highest wind gusts around 30 knots. these so far
have appeared slightly underdone tonight with both Ship John and
Cape May gusting slightly over 30 knots. However, a few 35 knot
gusts can not be ruled out so will leave the gale warning up.

For Friday...the winds should ease 3 kts or so on DE bay but some
of the guidance is suggesting increasing wind NJ coast, especially
NNJ later in the day. Therefore the gale watch. 


Fri night-Sat...Gale watch much of NJ coast early Fri night. SCA
in effect upper De Bay through Friday night, which may need to be
extended into Saturday. Atlc De and Cape May Atlc waters will
probably be SCA Fri night. 

Saturday night...Winds expected to drop below SCA levels, but
pick up again late Sunday.

Sunday-Sunday night...Winds may increase and approach SCA levels.

Monday...SCA conds psbl.


MARINE...Gale Watch from 6 AM EST Friday through late Friday night for 
     Small Craft Advisory until 6 AM EST Friday for ANZ450>452.
     Gale Warning until 6 AM EST Friday for ANZ431-453>455.
     Small Craft Advisory until 6 AM EST Saturday for ANZ430.


Near Term...Drag/Gaines

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