Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
352 am EDT Friday Jul 31 2015
a weak front will stall to our south and east today while weak
high pressure is centered to our west. The next weak cold front is
forecast to cross our area late Saturday into Sunday, then stall
offshore during Sunday into Monday. A stronger cold front is
expected to arrive later Tuesday, then stall nearby Wednesday into
Near term /until 6 PM this evening/...
what a difference a day can make! Drier air has been filtering into
the region through this morning and it certainly feels gorgeous out
Temperatures today will still rise into the upper 80s to lower 90s.
However, with those lower dewpoints in place, it will not feel quite
that hot outside. Plenty of sunshine as the clouds leave US for the
Overall, a beautiful Summer Friday for our region.
Short term /6 PM this evening through 6 am Saturday/...
the beautiful day turns into a beautiful night. Dry air remains
across the region and some slightly cooler temperatures will work
their way in as we retain that northwest flow into the evening
before it becomes southwesterly overnight.
Lows will drop into the 60s to around 70 through much of the area.
Long term /Saturday through Thursday/...
the synoptic setup is comprised of an upper-level trough from the
Great Lakes to the northeast that amplifies some Saturday into
Sunday. A weak front moves through late Saturday into Sunday, then
the next one which could be stronger arrives during Tuesday before
stalling nearby Wednesday into Thursday. The convective chances will be
determined by how much moisture return can occur ahead of each
surface front, and the actual amplitude of the trough and its
associated large scale ascent. We used a model blend Saturday
through Monday, then went with a wpc/continuity blend thereafter.
For Saturday and Sunday...an upper-level trough remains across the
northeast although it should weaken some Sunday as it reloads across
the Midwest. A frontal zone is forecast to move through late
Saturday into Sunday, and the greatest lift and shear is mostly from
near our northern zones on northward into New England. The dew
points should start to inch back upward again later Saturday,
however low enough moisture levels may limit convective development.
Some guidance does initiate more convection by late Saturday from
northeastern Pennsylvania to northern New Jersey then slides it
southeastward. There may be enough shear with increasing instability
to allow for a gusty thunderstorm, however this is dependent on the
air mass moistening up sufficiently as the upper-level trough
remains in place. For now, we continued some slight chance probability of precipitation across
the northern areas Saturday afternoon for the potential for at least
some isolated thunderstorms.
The front looks to stall offshore given weaker flow with a
southeastern extent, however some weak impulses may track along it.
It appears that any convection leftover with the front is offshore,
therefore we maintained a dry Sunday. It will continue to be warm to
even hot however the dew points are expected to remain low to not
really have an impact /although some increase should begin Sunday
night especially across the southern and eastern areas/.
For Monday and Tuesday...as the upper-level trough reloads from the
west, it may support weak impulses traversing the offshore front
however these look to remain separated from the incoming amplifying
trough. The upper-level flow turning more southwesterly for a time
will help pull some low-level moisture northward, resulting in at
least some mugginess returning. Some large scale ascent with the
trough along with a cold front arriving during Tuesday should result
in some showers and thunderstorms. The stronger shear and lift
however may glance our area, and as a result the model guidance
shows variation in the convective chances and coverage. We carried some
slight chance probability of precipitation mostly Monday afternoon, then low chance for Tuesday.
For Wednesday and Thursday...as the upper-level trough starts to
weaken in the northeast, the frontal boundary from Tuesday should
slow or even stall in our vicinity. This could help focus some
convective development especially during peak heating, although as
of now the overall forcing looks weak and more concentrated back
into the Ohio Valley associated with an impulse /possibly
convectively induced/. There is increased uncertainty as the chance for
showers and storms will depend on the positioning of the upper-level
trough, the frontal zone placement and possible surface wave
development. The air mass looks to be cooling though during this
time frame and this is reflected in the high/low
Aviation /08z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today...MVFR/IFR early at kmiv and kacy, where more low level
moisture remains in place. Expect improving conditions with VFR
returning to those sites around 12-14z. Elsewhere, drier air has
started to filter in and VFR conditions prevail. Skies will remain
clear through much of the day with few clouds around.
Light winds this morning will become west to northwest around 8 to
12 knots for this afternoon.
Tonight...VFR conditions expected. Few to no clouds around. Winds
will subside during the evening and overnight, gradually turning
more to the southwest.
Saturday...VFR overall. A few possible showers or thunderstorms in
the afternoon and evening mainly north of kphl.
Monday and Tuesday...some showers and thunderstorms possible
especially during Tuesday afternoon, otherwise VFR.
west to northwest winds will be around 10 to 15 knots this morning
and then subsiding a bit toward this afternoon and evening. Winds
will gradually turn more to the southwest toward this evening and
overnight. Seas will generally remain in the 2 to 4 foot range.
Saturday through Tuesday...the conditions overall are anticipated to
be below Small Craft Advisory criteria. A southerly flow Saturday
should increase ahead of a weak cold front with gusts to about 20
knots for a time, and this looks to occur again later Monday ahead
of another cold front. This will result in an increase in the seas
at times, although currently expecting these to remain under