Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 211602

Area Forecast Discussion
National Weather Service Mount Holly NJ
1202 PM EDT Fri Oct 21 2016

Low pressure will strengthen across Pennsylvania today and move
up into New England Saturday. A strong cold front will cross the
area tonight. The low will continue to deepen and move into Quebec
on Sunday. A fast moving weak disturbance will cross New York and
New England Sunday night and early Monday. High pressure will
build in for much of next week.


Showers tapering off along the coast, and the heaviest rain
remains over the ocean. Some scattered showers will continue to
track along the coast, but additional rainfall will be light.

Line of showers developing over central PA ahead of the
approaching cold front. Based on latest HRRR, looks like those
showers should begin to get into far western zones by late
afternoon/early evening.

Very warm and humid airmass remains across the region with highs
well into the 70s for most of the area, possibly into the low 80s
across southern zones. Dewpoints will be well into the 60s.


Low pressure will track northeastward across the area this evening.
This system will be accompanied by a strong cold front that will
pass through the area. This low will eventually merge with the
offshore system overnight, resulting in a rapidly deepening cyclone
over New England.

Gusty northwest winds will develop behind the cold front as the low
rapidly deepens upstream and the pressure gradient tightens. Strong
CAA advection will steepen lapse rates in the boundary layer which
will allow stronger winds aloft to mix down to the surface later
into the night. The strongest wind gusts of around 30 mph will
likely first appear  in the southwestern portion of the forecast
area overnight. Temperatures will quickly fall into the 40s and 50s
overnight behind the front.

Showers are likely along the front to pivot eastward through the
area tonight. Tried to reflect the best chance for showers in the
PoP/Weather grids based on the forecast timing of the front. A brief
downpour is possible with these showers but do not expect heavy
rainfall totals as the cold front will be progressive. Did not see
enough support from the high-res NCAR ensembles to include thunder
in the forecast.


Saturday thru Sunday...Deep low pressure will continue to
circulate cool air across the region. Temperatures both days will
be much more like October than of recent days. Sat will be some 5
degrees below normal and by Sunday readings will moderate back to
normal values. Gusty winds, especially Saturday, will give the air
a brisk fall-like feel. Winds may gust 35 to 40 mph Saturday, but
will be a little less on Sunday.

A quick and weak disturbance will cross north of the area Sunday
night and it may bring a few gusty showers to the southern Poconos
and northern NJ. Pops for the present fcst will just be in the
slight chc range, since the air may be too dry for any measurable
precipitation to occur. Temperatures Monday will be like Sunday,
near normal. A cold front will cross the area behind the
disturbance Monday.

Tue thru Wed night...dry weather expected with high pressure
building in. Temperatures will be mostly below normal with the
upper trough settling across the area Tue. The trough will then
move away Wed.

Thu...OP models show the next disturbance, a deep low moving
across the Great Lakes, beginning to affect our weather Thu. We
have indicated increasing clouds and chc pops for Thu attm.


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

Conditions have improved to VFR across the terminals, and VFR
should remain in place through the afternoon.

Lower clouds should return this evening. Showers are likely
tonight with a cold front moving thru. Post-frontal stratocu may
prolong MVFR CIGs through the rest of the night.

An abrupt windshift from south to northwest is expected with the
fropa. Gusty NW winds arrive shortly after the fropa late tonight.
The gustiest winds are expected overnight across southern and
western terminals.

.Sat...Mostly VFR with gusty winds. Few showers with restrictions
possible N/W Sat morning.
.Sat night/Sun...VFR with gusty winds.
.Sun night/Mon morning...Mostly VFR but a few showers far North.
.Mon afternoon thru Tue...VFR.


Today...Southeast winds 5-15 kt this morning while seas in the
coastal waters are 3-4 ft. The pressure gradient will weaken this
afternoon, causing the winds to become light and variable as the
waters become situated in between two areas of low pressure (an
offshore low that will drift northward about 150 miles east of our
coastline and another low moving across central PA). There may be
some isolated lightning tied to the offshore system this afternoon
if stronger convection develops but the bulk of the high-res CAM
guidance keeps this offshore. Kept thunderstorms out of the
forecast for our coastal waters for now.

Winds will quickly shift from south to west-northwest this evening
in concert with a strong cold fropa. Post-frontal winds speeds are
forecast to increase to SCA levels, first in the DE Bay and southern
coastal waters during the late evening and then in our northern
coastal waters overnight. Models have trended a bit slower with the
arrival of the steadier pressure rises and strong CAA behind the
front. Therefore, gales may not occur until overnight in the DE
Bay/southern coastal waters and not until early Saturday morning
across the northern waters. The Gale Watch was upgraded to a Warning
but the onset time was adjusted accordingly.

Sat thru Sunday...Gale conditions across the waters, ending first
over Delaware Bay Sat night and then across the southern Atlantic
waters around noon Sunday. Scattered showers over the northern
coastal waters Sat morning, otherwise fair weather expected.

Sun night thru Tuesday...SCA conditions expected.

Tue night thru Wed...Mostly sub-SCA conditions.


MARINE...Gale Warning from midnight tonight to noon EDT Sunday for
     Gale Warning from 4 AM Saturday to 6 PM EDT Sunday for ANZ450-
     Gale Warning from midnight tonight to 2 AM EDT Sunday for


Near Term...MPS
Short Term...Klein
Long Term...O`Hara
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