Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
616 am EDT Wednesday Aug 27 2014
high pressure will exit the region as a cold front crosses the
area later today. Hurricane Cristobal will pass well east of the
New Jersey and Delaware coasts late tonight into Thursday. High
pressure will then build in from the west once again for Thursday
into Saturday. A cold front will then move through the area from
the northwest Sunday into Monday.
Near term /until 6 PM this evening/...
the sky over our region was mostly clear at 600 am. A light wind
and relative humidity values of 95 percent or greater at some
locations has resulted in the development of patchy fog and
stratus. We are anticipating a mostly sunny morning with the heat
of the sun dissipating any early morning low clouds and fog rather
Temperatures should rise through the 70s this morning and into
the lower 80s by midday at most locations. We continue to
anticipate maximum temperatures around 90 degrees this afternoon,
except in the elevated terrain up north and along the immediate
The axis of a middle level short wave was located over the western
Great Lakes region early this morning. The feature will progress
eastward and it should reach southeastern Ontario late this
afternoon. Clouds are forecast to begin overspreading our
northwestern counties late this afternoon along with a low chance
of showers and thunderstorms.
Short term /6 PM this evening through 6 am Thursday/...
the middle level short wave is expected to pass over the
northeastern states tonight and it should push a cold front
through our region. The frontal boundary is expected to enter our
northwestern counties this evening and it will likely pass to our
southeast late tonight.
Our best chance for showers and thunderstorms appears to be this
evening, mainly across our northwestern counties where some
instability will develop. Mixed layer cape values may reach the
500 to 1000 j/kg range in the Poconos and perhaps in adjacent
areas of the Lehigh Valley and northwestern New Jersey. The loss
of daytime heating will cause conditions to stabilize and any
thunderstorms are expected to weaken as they move southeastward
into southeastern Pennsylvania and central New Jersey during the
An area of cumulus and stratocumulus associated with the cold
front should drop southeastward over our region during the night
along with a few lingering light rain showers. Most of the clouds
and any precipitation are forecast to be to the south and east of
southern Delaware by daybreak on Thursday.
Temperatures are expected to drop into the 60s tonight in most of
our forecast area.
The center of Hurricane Cristobal should pass more than 400 miles
to our southeast tonight and it will have no impact on our
weather. However, it will bring increased waves and long period
swells to the coastal waters of Delaware and New Jersey.
Long term /Thursday through Tuesday/...
at the start of the extendd pd, high pressure was located near the
Great Lakes and hrcn Cristobal was well off the eastern Seaboard moving NE.
Cristobal will make its closest approach to the area Erly Thursday
before pulling quickly away.
Then, the aforementioned high pressure will build eastward over the region
for Thursday into Sat bringing dry and increasingly warm weather as the 500 mb
ridge builds in.
A warm front will move to our north on Sat, but despite this feature, the
latest guidance has trended drier, and have removed all pops, though a
stray shower can not be ruled out.
By sun, the temperatures warm even further as the ridge remains in place
and the southwesterly flow increases. The models differ somewhat on precipitation
chances. The European model (ecmwf) is mainly dry on Friday. It does bring some late
showers/thunderstorms and rain to northern and western sections. The GFS and CMC have much more
precipitation around. Clearly, in this type of weather pattern the potential for
mainly diurnal showers/thunderstorms and rain is there, but the European model (ecmwf) may be on to
something with its slower progression, as the high is quite
strong. For now, will just carry low chance probability of precipitation.
The best chance of precipitation comes later Sunday into Monday when a cold front
will approach and cross the area. Again, models differ a bit on
timing. The GFS is faster (no surprise) and is basically dry after
12z. The European model (ecmwf) lingers some precipitation during the day on Monday. Generally the
European model (ecmwf) is too slow with frontal passage timing,. But again, in this pattern with
the strong high, the potential is there.
Then, by Monday night into Tue, the front clears the area, weak high
pressure builds back in and a dry day is in store for the long ride
home after the Holiday weekend.
Temperatures will be at or above normal through the pd, and Sat looks to be the best
day of the Holiday wknd, and sun could end up being not all that
bad, especially over southern and eastern areas.
Aviation /10z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
The sky over our region was mainly clear at 1000z. There will be
patchy fog and stratus early this morning, especially around krdg,
kabe and kmiv. Otherwise, mainly VFR conditions are forecast
through the taf period. The sky is expected to be mostly sunny for
today with an increase in clouds from the northwest late this
A cold front approaching from the northwest may bring scattered
showers and thunderstorms to krdg and kabe this evening. The
precipitation is expected to weaken and dissipate as it moves
southeastward early tonight.
A light and variable wind early this morning is forecast to
settle into the southwest around 4 to 8 knots for today. A cold
frontal passage tonight is expected to cause the wind direction to
shift to the northwest. Speeds will likely remain mostly in the 4
to 8 knot range.
Thursday through Sat...VFR and dry with high pressure. High
confidence. Can not rule out the slight chance of a rain showers/thunderstorms and rain on
Sat but chances are too low to mention at this time.
Sun...mainly VFR. Rain showers and thunderstorms and rain chances, mainly west as cold front
approaches. MDT confidence.
wind speeds are forecast to remain below the Small Craft Advisory
criterion for today and tonight. The direction will favor the
southeast to southwest today and it is expected to shift to the
northwest late tonight.
Swells from Hurricane Cristobal will affect the coastal waters of
Delaware and New Jersey during today and tonight. Wave heights are
forecast to increase into the 5 to 7 foot range. A Small Craft
Advisory begins at 1000 am for our ocean waters from off Atlantic
City southward. A Small Craft Advisory begins at 200 PM for our
northern ocean waters. Long period swells of 12 to 16 seconds will
likely create particularly rough conditions around the inlets
along the coasts of Delaware and New Jersey.
Thursday..based on the latest NHC track of Hurricane Cristobal, it
should make its closest pass to US early Thursday and then move rapidly
away from the area by later Thursday. As a result, seas are expected to
remain elevated for much of the day and the Small Craft Advisory has been extended
into Thursday. By later Thu, seas should decrease as Cristobal moves
away, but less confidence in just how quickly they subside. The
Small Craft Advisory may need to be extended a bit longer.
Thursday night through sun...seas will continue to subside early in
the period and remain below Small Craft Advisory criteria. No marine headlines expected
through the weekend.
long period swells from Hurricane Cristobal will result in a high
risk of dangerous rip currents along the coasts of Delaware and
New Jersey for today into tonight. The elevated threat of
dangerous rip currents will likely continue into Thursday.
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 from 10 am this
morning to 6 PM EDT Thursday for anz452>455.
Small Craft Advisory for hazardous seas from 2 PM this
afternoon to 6 PM EDT Thursday for anz450-451.