Area Forecast Discussion
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FXUS61 KPHI 082051
Area Forecast Discussion
National Weather Service Mount Holly NJ
351 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.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Morning summary: had a smattering-scattering of .01 rainfall this
morning southern 2/3rds De and a ptn of Md E shore.
Remainder of this afternoon...west wind will continue increasing
to 22-28 kt around 21z then should decrease after sunset but PHL
may gust 18-20 kt all night.
Note: tonights low temp fcst at PHL will be the coldest of the
season so far at PHL and remember last winter, it didnt drop into
the 20s until January 4th 2016!
Tonight...mostly clear with 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.
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.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
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.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
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 erly Wed, while the GFS 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 patn.
.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY and surrounding areas.
Remainder of this afternoon...VFR sct clouds aoa 4000 ft. West wind
with gusts increasing 22 to 28 kt by 21z. Already 25 kt PHL.
Tonight...VFR mostly clear. wnw wind with scattered gusts 15-20
kt, mainly PHL area.
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.
Gale warning posted for lower De Bay and adjacent DE, Cape May
waters. A gale watch is posted for Fri-Fri eve per collab with
Many reports 29kt upstream mid afternoon.
The wind orientation down De Bay, steep lapse rates possibly
manufactures several more kts of wind than modeled in the caa
pattern. NAM sounding indicates mid 30s gales possible.
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 Friday morning through late Friday night for
Small Craft Advisory until 6 AM EST Friday for ANZ450>452.
Gale Warning until 6 AM EST Friday for ANZ453>455.
Small Craft Advisory until 6 AM EST Saturday for ANZ430.
Gale Warning until 6 AM EST Friday for ANZ431.