Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
911 am EDT Sat Jul 30 2016
as a weak frontal boundary remains near our area today into early
next week, a few weak low pressure systems will track along it.
High pressure will build across our area Tuesday through Wednesday
before shifting offshore Thursday, then a cold front is scheduled
to arrive Friday night.
Near term /until 6 PM this evening/...
We are anticipating a break in the potential for showers in our
forecast area until about noontime when the hrrr and rap both show
a quick uptick in shower and thunderstorm coverage across the
region. Showers and thunderstorms are expected to become more
numerous during the afternoon as an impulse traveling in the mid
level flow begins to approach from the west. An isolated strong to
severe storm this afternoon can not be ruled out across Delmarva
with an environment marked with 1000-2000 j/kg surface and mixed
layer cape coupled with about 30 knots of 0-6 km bulk shear. A
developing south to southeast surface flow will draw additional
moisture into our region. Precipitable water values are forecast
to increase to around 2.0 to 2.1 inches. As a result, the rain may
become heavy at times.
We are expecting an increase in overall cloud cover today and
temperatures should not get above the 80s.
Short term /6 PM this evening through 6 am Sunday/...
we continue to expect showers and scattered thunderstorms for
tonight as a couple of mid level impulses affect our region and as
a warm front approaches from the southwest and south. We will keep
the mention of rain, heavy at times, due to additional low level
moisture advecting into our region on a southeasterly flow off the
Overnight minimum temperatures are forecast to be in the upper
60s in the Poconos and far northern New Jersey and mainly in the
lower 70s in the rest of our region.
Long term /Sunday through Friday/...
the synoptic setup is comprised of general troughing in the
northeast to start that then becomes more amplified during early
next week. This should shift offshore midweek as some ridging
starts to migrate eastward from the plains. The ridge axis may not
arrive until Friday, therefore a cooler airmass is for a few days
next week. We used a model blend for Sunday into Tuesday, then
mostly went with the 00z wpc guidance. Some adjustments were then
made however following additional collaboration with our
For Sunday and Monday...a couple of short waves will move across
our region as a frontal boundary remains in the vicinity. The
result will be some showers and thunderstorms. While the specific
timing of the short waves is less certain, the more widespread
convective activity should occur during peak heating and
potentially be more focused initially along a weak surface
convergence zone. The precipitable water values are forecast to be around 2.00
inches and therefore locally torrential downpours can occur. While
any flood threat should be localized Sunday, weak low-level flow
may result in slow movers and back building of any thunderstorms.
Any robust convection may produce quite a bit of lightning.
Overall, the severe weather threat looks rather low at this time.
For Monday, an upper-level trough sharpens and with some cooling
aloft and increase in the wind fields, a few locally stronger
storms may occur during the afternoon.
For Tuesday through Thursday...a cold front should be south and
east of our area to start Tuesday, as high pressure builds in.
This surface high is forecast to be in place through Wednesday
before it shifts offshore Thursday. We are anticipating some
lowering of the dew points and also the temperatures. Some return
flow however starts to develop on Thursday, which should allow the
dew points to inch back up some.
For Friday...high pressure to our south and east will yield to a
warm front lifting well to our north. This will help assist in a
more south-southwest flow as a cold front approaches in the
afternoon, then the front should start settling across our area at
night. An area of warm air advection ahead of the front will allow
for afternoon temperatures to approach 90 degrees especially from
the Interstate 95 corridor on south and east. The overall timing
of the front will govern any convective threat as it appears that
a Lee side trough may not be present. We carried slight chance to
low chance pops from west to east Friday afternoon and night.
Aviation /13z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR,however, showers and scattered thunderstorms are expected to
be on the increase as the day progresses. Ceilings and visibility
values are anticipated to lower to MVFR and perhaps IFR tonight as
a warm front approaches from the southwest and south.
The wind direction should favor the south for today and it will
likely become southeast for tonight. Speeds are forecast to be
mostly less than 10 knots.
Sunday and Monday...potential for MVFR ceilings to start each
morning, otherwise VFR with scattered to broken cloud cover. Some
showers and thunderstorms will be around especially Sunday and
this will lead to mainly local and brief restrictions.
Tuesday and Wednesday...VFR overall as high pressure builds in.
the wind is expected to settle into the south and southeast for
today around 5 to 10 knots. The wind is forecast to favor the
southeast for tonight and speeds may increase to 10 to 15 knots as
a warm front approaches from the southwest and south.
Wave heights on our ocean waters are expected to be 2 to 3 feet
for today and tonight. Waves on Delaware Bay should be 2 feet or
Showers and scattered thunderstorms are anticipated from this
afternoon into tonight.
Sunday through Wednesday...an onshore flow Sunday should increase
some especially across the northern coastal waters, with gusts to
about 20 knots. It appears at this point that that conditions
remain below advisory criteria. Otherwise, a weak pressure
gradient should keep winds and seas mainly below Small Craft
Advisory criteria through Wednesday. Main concern will be the
threat of some thunderstorms Sunday and Monday, however the
greatest concentration of storms may be inland.
for today, there is a low risk for the development of dangerous
rip currents along the coasts of New Jersey and Delaware. The wind
direction should favor the southeast at 5 to 10 miles per hour with wave
heights in the 2 to 3 foot range. We are anticipating a southerly
swell with a wave period around 6 seconds.
For Sunday, a low risk overall. However a moderate risk is
possible mainly along the northern New Jersey coast although this
will be dependent on the strength of an onshore flow.