Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 062211

Area Forecast Discussion
National Weather Service Mount Holly NJ
511 PM EST Tue Dec 6 2016

High pressure over the northeast will give way to developing low
pressure off the Carolinas into tonight. Meanwhile, low pressure
nearing James Bay sends a cold front thru our area on Wednesday,
sweeping the Carolinas low well offshore. The low pressure over
James Bay will move to Atlantic Canada into Friday, while high
pressure over the central United States moves into the middle
Atlantic this weekend. A warm front may approach our region by



5:00 pm update: During the wetbulbing process across Eastern PA
and into northern and central New Jersey some sleet is mixing
with the rain. No sleet accumulation is expected in most spots
given temperatures are several degrees above freezing. Temperatures
and dewpoints will stay steady or rise. So while sleet may mix in
through the early evening a change to rain is still expected in
elevations less than 1,000 feet. MPO has changed to snow and
should remain snow through the evening. Accumulations of a few
inches in the highest elevations remain on track.


A double-barrel low pressure system is expected to combine energy
off the Carolina coast this evening, then intensify before the
system moves slowly northeast out over the Atlantic on Wednesday.
Precipitation associated with this system has already overspread
the CWA this afternoon, with a brief period of sleet reported on
the leading edge. The atmospheric profile still looks conducive
for snow in the far north (Carbon/Monroe/Sussex counties),
especially in the higher elevations, and since current QPF
guidance is similar to previous runs, 2 possibly up to 4 inches
mainly above 1000 feet still looks plausible, with several hours
of moderate snowfall possible in those areas this evening. The
current Winter Weather Advisory will therefore continue through
the overnight hours. Easterly winds this afternoon generally under
10 mph are expected to veer to the northeast during the overnight
hours as the speed increases to around 15 to 20 MPH with higher
gusts near the coast. Areas that see mainly rain (generally south
of I-80) can expect around one-half inch of precipitation from
this event, with light rain or drizzle after midnight.


As the low continues to move out to sea, precipitation will end
during the morning hours basically from southwest to northeast...and
any remaining wind gusts (especially closer to the coast) will
gradually diminish as the pressure gradient relaxes. Expect cloudy
conditions in the morning...with gradual improvement from west to
east as the day wears on. Northwest winds are expected around 10
MPH...perhaps slightly stronger along near the coast.


Temperatures will continue to be mild on Thursday, ahead of an
approaching cold front. Models are in better agreement backing
off on precip for Thursday however will hold on to a slight chance
of rain due to increasing moisture. The long wave trough and
attendant cold front continues east, pushing the cold front across
the the region late Thursday into Thursday night.

High temperatures on Friday will be mainly in the 30s to lower
40s. A few snow showers occuring beneath the cold mid level
trough and downstream from the Great Lakes may make it into the
far northwest corner of the forecast area on Friday, mainly
northwest of I-95-276-76 where the BTV Snow Squall Parameter
values are the highest. Models are also in a little better
agreement bringing precip in Sunday night into Monday. The cooler
temperatures will continue into Saturday.

Models are also in a little better agreement for early next week.
bringing the next storm system across the region late Sunday into
Monday. GFS thermal profiles support wintry precip initially with
a changeover to rain Monday, while the slower ECMWF is much
warmer, suggesting a primarily rain event. Given the antecedent
cold air mass in place, wintry precip is plausible at the onset,
with a changeover to rain.


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

IFR conditions expected through the evening hours at many TAF
locations as bands of moderate rain move through. SN could mix in
with RA for brief periods at RDG and ABE...but no major problems are
expected. Rain is expected to taper off from SW to NE late tonight,
but low clouds will remain over the area through a good portion of
the overnight hours, with lingering IFR conditions.

NE winds around 10 kt with higher gusts closer to the coast are
expected tonight. Northwest winds in the 5 to 10 KT range are
expected on Wednesday as the low continues to move out to sea.

Predominantly VFR at all TAF sites through the period.

Northwest winds may gust up to around 25 knots Thu night into


A Gale Warning continues for tonight for the coastal waters of DE
and S NJ as well as the lower DE Bay as easterly winds strengthen to
the north of the coastal low. A SCA continues for the northern
coastal waters and for the upper DE Bay with gusts 25-30 kt possible
tonight. 4-7 ft seas are expected in response to the strengthening
wind field. Although northwest wind gusts are expected to remain
below 25 knots on Wednesday, seas are forecast to remain elevated,
at or above 5 FT. Thus, a Small Craft Advisory for hazardous seas
may be needed for the ocean waters.


Gusts over 25 knots from the northwest are likely Thursday night
and Friday with some potential to reach gale force. Winds will
decrease on Saturday below 25 knots from the northwest. Seas are
likely to remain below five feet for the outlook period.


PA...Winter Weather Advisory until 6 AM EST Wednesday for PAZ054-
NJ...Winter Weather Advisory until 6 AM EST Wednesday for NJZ001.
MARINE...Gale Warning until 6 AM EST Wednesday for ANZ452>455.
     Small Craft Advisory until 6 AM EST Wednesday for ANZ450-451.
     Small Craft Advisory until 4 AM EST Wednesday for ANZ430.
     Gale Warning until 4 AM EST Wednesday for ANZ431.


Near Term...Gaines/Miketta
Short Term...Miketta
Long Term...Runyan
Marine...Miketta/Gaines is the U.S. government's official web portal to all federal, state and local government web resources and services.