Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1228 am EDT Thursday Aug 28 2014
a weak cold front will slide across the region tonight, helping
to keep Hurricane Cristobal well east of the middle Atlantic coast
into Thursday. High pressure builds in Thursday and Friday, then
shifts offshore into Saturday. A warm front should lift north
across the region Saturday, then a frontal boundary may stall to
our north Sunday and Monday. The next cold front is scheduled to
Near term /until 6 am this morning/...
the cold front extended from around Perth Amboy to Trenton to
Norristown to Coatesville around midnight it will continue to drop
southward through the remainder of our forecast area before
An isolated shower lingered near Hazleton in Pennsylvania.
Another more substantial shower with isolated lightning was
located in Morris County, New Jersey around Denville and Boonton.
There was one additional light shower near Warren township in
Somerset County. The precipitation should continue to weaken and
eventually dissipate as it moves southeastward. We will remove the
mention of precipitation from the forecast based on its very
limited coverage and on the expectation that it should either
dissipate or move out of our forecast area by about 130 am.
A light northwest wind will continue to develop in the wake of
the cold front and temperatures should drop into the 60s at most
locations. The sky is expected to clear from northwest to
southeast with perhaps some clouds lingering over our southeastern
counties at daybreak.
Short term /6 am this morning through 6 am Friday/...
the cold front is expected to moving south of the Delaware-Maryland-Virginia during
the morning on Thursday. High pressure will build in from the
Great Lakes behind the front. The official NHC forecast calls for
Hurricane Cristobal to be located about 500 miles off the middle-
Atlantic coast 12z Thursday before accelerating to the east-
northeast, moving farther out to sea during the day.
The pressure gradient between the high to our northwest and the
cold front to our South/Hurricane Cristobal to our east will
produce a breezy northwest wind 10-15 miles per hour across our area. These
winds will usher in relatively cool and dry air with the source of
this Post-frontal air mass from Canada. Forecast maximum temperatures in the
lm80s for most of the region, except mu70s in the mountains.
Long term /Friday through Thursday/...
the overall synoptic setup is comprised of an upper-level trough
exiting the northeast Thursday night into Friday, then a short
wave trough tracking across the northern plains and Midwest will
build a ridge across the east Friday and into the weekend. This
ridge may hold for awhile, however additional short waves will
carve out another upper-level trough that eventually shifts
eastward across the Midwest and Great Lakes region. An associated
cold front should arrive toward the end of this time frame,
although an initial front may stall to our north before retreating
northward. We used a model blend for Thursday night through
Saturday, then went with the 12z wpc guidance. Some adjustments
were then made following additional collaboration with our
For Thursday night and Friday...an upper-level trough will be
exiting to our east followed by some ridging. This will push high
pressure across the northeast and middle Atlantic regions. The center
of the surface high will probably be located just to our north,
therefore a northwest to north surface wind should occur. This
will help advect a drier air mass into the area along with cooler
air through Friday. However, the surface high should be shifting
offshore Friday night allowing for a return flow to start becoming
established. A system moving across the northern plains and
Midwest will assist in warm air advection developing northbound up the Ohio
Valley. This should also organize a warm front to our southwest.
For Saturday and Sunday...the building of an upper-level ridge is
forecast to occur during this time frame, however short wave
energy traveling from the Midwest to the Great Lakes region will
try and flatten it some. Due to the ridge and also surface high
pressure situated offshore, a southwesterly flow of warm/hot and
increasingly more humid air will overspread the area. While there
may be somewhat of a moisture surge as a warm front lifts north
across the area Saturday, the overall forcing looks weak with much
of the energy focused closer to the Great Lakes. Therefore, we
maintained a dry forecast for Saturday. An initial disturbance may
end up weakening as it traverses a frontal boundary to our north
and west Sunday as it runs into the northwest flank of the upper-
level ridge. Despite this, there could be some convection on the
southeastward flank of this weakening disturbance Sunday. If a Lee
side trough develops, this could also be the focus for some
convective development within the large warm sector. Given the
heat and higher humidity in place, some thunderstorms could be
locally strong from our western zones and especially west of our
County Warning Area. This carries lower confidence though due to some uncertainty
on convective initiation and coverage and the timing of embedded
features. For now, we carried chance probability of precipitation or less during Sunday.
For Monday and Tuesday...as an upper-level trough reloads across
the northern plains and Midwest Monday, a ridge is still near our
area maintaining a southwesterly flow. There appears to be a
stalled baroclinic zone though to our north, however as of now
there is no real strong surface high to push this southward, plus
the ridging farther south may be strong enough to keep it at Bay.
However, the model guidance suggests that within a rather warm and
moist air mass a Lee side trough may be present and even sharpen up
some. With any subtle short waves tracking around the northwestern
periphery of the lingering ridge, some convection could develop in
tandem with the Lee side trough. As a result, we will carry slight
chance to lower chance probability of precipitation especially inland. There are some timing
differences in the model guidance, therefore we followed more
closely to the 12z wpc guidance.
For Wednesday...an amplifying upper-level trough from the Midwest
and Great Lakes region should push a cold front into our region.
While there are some timing differences in the model guidance, we
did stay closer to wpc guidance. This brings the actual cold front
into our area later in the day. As heights fall, the front arrives
and large scale forcing generally arrives, some convection is
possible. If this occurs during peak heating with enough shear,
convection could be more organized. Overall, we went rather close
to the 12z wpc guidance.
Aviation /04z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conditions are expected through the taf period. Occasionally
broken ceilings around or above 4000 feet should clear from
northwest to southeast during the overnight period. A mostly
clear sky is anticipated for Thursday.
A light northwest wind will develop overnight. Wind speeds are
forecast to increase into the 8 to 12 knot range on Thursday with
gusts near 20 knots, especially in the afternoon.
Thursday night and Friday...VFR. Light winds becoming northeast,
and then southerly Friday.
Saturday and Sunday...a chance of local fog each early morning,
otherwise mainly VFR. Some increase in clouds possible Saturday as
a warm front lifts northward. Some showers and thunderstorms are
possible Sunday, with a chance for locally sub-VFR conditions.
South and southeast winds Saturday 5-10 knots, becoming south-
Monday...VFR, with the exception of possible brief times of MVFR
associated with a shower or thunderstorm. Lower confidence
regarding precipitation coverage. Southwesterly winds generally
near 10 knots.
as of midnight...seas at buoy 44009 are still holding at 4 feet.
Still believe that swells from Cristobal will affect the New Jersey and Delaware
coastal waters later tonight and during the day on Thursday. Maximum
seas are now expected to be around 6 feet.
as tropical cyclone Cristobal moves farther away from the area,
the swells are expected to subside. While 5-foot swells may
persist a little longer Thursday night, we held off on extending
the Small Craft Advisory at this time due to some uncertainty. High
pressure builds in over the weekend before shifting offshore and
allowing for a return flow into next week. The flow may strengthen
for a time Sunday into Monday, however overall the conditions are
anticipated to be below Small Craft Advisory criteria.
long-period swells from Hurricane Cristobal have been slower to
reach New Jersey and Delaware beaches compared to wave model guidance.
However...higher swells have been noted farther south along the
Atlantic coast and these are still expected to spread northward over
night and continue on Thursday as Cristobal churns up the waters
500 miles or so east-southeast of Delaware Bay. The high risk of rip currents
has therefore been extended through Thursday into Thursday
The media and decision makers can help. All 4 rip current
fatalities at New Jersey beaches this year were at unguarded locations!
There isnt much more we can say except that family members and
friends may think they're strong enough to keep you safe but its
risky. Like it or not...the water is far more powerful than you
think. Swimming in the ocean is not swimming in the local pool.
Its probably more tiring because of long shore currents along the
beach and the sweeping crashing motion of the waves breaking
inward and then the outgoing water returning to sea as rip
New Jersey...high rip current risk through this evening for njz014-024>026.
Delaware...high rip current risk through this evening for dez004.
Marine...Small Craft Advisory for hazardous seas until 6 PM EDT this
evening for anz450>455.