Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 260622

Area Forecast Discussion
National Weather Service Mount Holly NJ
222 AM EDT FRI AUG 26 2016

A weak cold front moves across the region on Friday, and then
remains nearly stationary just south of the region through the
weekend. High pressure builds to the north this weekend and then
moves off the New England Coast on Monday. Another high settles
over the area into the middle of the new week, but a series of
weak disturbances will pass through the region during this time.


Through 12z today, a pre-frontal trough is positioned just to our
west. While the instability is weakening with time, there remains
enough to maintain or redevelop some showers across portions of our
west/northwest zones. The forcing is not well defined, therefore it
appears that a warm/moist airmass in place combined with the pre-
frontal trough is just enough to keep some showers going for awhile.
Therefore, increased the pops across these areas at least into the
chance range for scattered activity.

An upper-level ridge still centered to our south will become the
main weather feature today. This ridge is forecast to actually build
a bit northward into our area by late afternoon. This will keep the
stronger flow from the Midwest to the Great Lakes then to New
England. At the surface, a weakening cool front will continue to
settle south and eastward across our area through midday. This
boundary may then end up dissipating during the afternoon as it is
mostly just a dew point boundary. Given the building ridge, there is
a very small window of opportunity for a shower or thunderstorm
mainly through midday. There will be more of a cap across the
southern areas due to the building ridge and then some drying occurs
from northwest to southeast during the course of the day across much
of the region. This coupled with a lack of defined forcing is not
good for convective chances. As a result, the forecast is currently
dry after 12z.

Some convective cloud debris is expected to move across at least
parts of the region this morning, however some increase in
subsidence especially this afternoon along with some drying should
allow for less cloud cover through the day across much of the area.
It will be hot however for most areas as the boundary layer flow
turns to the west and northwest for areas behind the weakening cool
front. The heat indices will be driven by how much the dew points
lower, however a humid day overall is expected with the highest heat
indices anticipated from about the Philadelphia metro on south and
east. It still appears that the heat indices fall short of advisory


As the upper-level ridge continues to build across our region
tonight, surface high pressure near the Great Lakes will slide
eastward. This will allow for a more northeasterly low-level flow,
although most places should have the winds decouple during the
evening. While some high level clouds may drift across from time to
time, overall a mostly clear sky is anticipated. It will be
mild/warm, however the dew points should actually drop some allowing
for a bit more radiational cooling. This is especially the case
across the northern areas where dew points are forecast to be the


High pressure builds into the Great Lakes region and will slowly
track east through the weekend. Northerly flow ahead of the high
will usher a much dryer airmass into the region on Saturday with
surface dewpoints falling from the upper 60s to near 70 Friday
evening to the upper 50s to around 60 by Saturday afternoon. High
temps will only be a few degrees cooler compared to Friday, but
conditions will feel more comfortable due to the lower humidity

The center of the high will pass over central NY/PA Saturday
night, and then moves off the New England Coast on Sunday. Return
flow sets up behind the departing high, and returns flow sets up
with surface dewpoints creeping back up into the mid and upper
60s, making it a bit more humid compared to Saturday.

Cold front then approaches on Monday and slowly passes through
the region on Tuesday. Isolated showers and thunderstorms are
possible Monday afternoon and evening, and then there is a better
chance for showers and thunderstorms on Tuesday with the passage
of the front. There currently is not much upper level support, so
will keep POPs capped at low end chance for now. Thereafter,
surface high pressure settles over the Great lakes and Ohio Valley
into the middle of the week. However, a series of weak upper level
shortwaves and vort maxes will pass through the region, touching
off isolated to scattered showers and thunderstorms during that
time. Will go no higher than low chance for POPs.

Temperatures will continue to run several degrees above normal
through the middle of next week, but should as hot as Friday.


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

Today...VFR overall. A ceiling mainly at and above 8000 feet for
a time this morning, then thinning out. A weak cool front settles
across the area, therefore most terminals will have a wind shift
to the northwest with an increase to around 10 knots. ACY should
take the longest to have a wind shift to the west. A few showers
will move across mainly early this morning in the ABE to RDG

Tonight...VFR. Northwest winds diminish early, then become northeast
or locally light and variable.

Saturday through Sunday night...VFR. Light N winds will become NE
on Saturday afternoon, and then will become SE on Sunday.

Monday through Tuesday...Mainly VFR. Isolated to scattered
showers and thunderstorms possible.


Southwest winds 10-20 kt will continue through the overnight
and early morning hours. During Friday, the winds should begin to
decrease as a weakening cool front arrives and a wind shift more
to the west takes place.

Friday night through Tuesday...High pressure passes well north of
the waters this weekend. A cold front approaches on Monday and
slowly passes across the waters through Tuesday. Sub-Small Craft
Advisory conditions expected to continue across the waters.

For today...The risk for the formation of dangerous rip currents
is low for the New Jersey shore and the Delaware beaches. However,
if winds remain backed more out of the south than what we are
currently forecasting, then a moderate risk could develop at our
NJ beaches.

The probable risk for the formation of dangerous rip currents
on Saturday appears to be low at this time.

Sunday through Wednesday...model ensemble guidance on every
successive cycle continues to send 2-4 ft long period (15 to 17
second) east southeast swell into our waters from the central
Atlantic - Gaston. It could be even higher but we`re taking the
conservative approach at this time from this distant offshore
hurricane. This is all dependent on size, strength and track but
there is little doubt that swells will build here...just how much
is the question. Swimming and wading dangers will probably
increase. For now we`re anticipating a moderate or greater risk
for Monday through Wednesday and possibly starting Sunday.




Near Term...Gorse
Short Term...Gorse
Long Term...MPS
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