Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
350 PM EDT sun Oct 4 2015
high pressure will remain in place through middle week. By Wednesday, a
weak cold front is expected to cross our region. On the heels of
this front, a high will build in through the remainder of the work
week. A stronger cold front should approach the northeast Friday or
Near term /until 6 am Monday morning/...
Wind Advisory remains in effect for the coastal strip of Cape May
and Sussex counties through 6pm. We have expired the advisory for
coastal ocean and coastal Atlantic counties at this time as the
winds have started to taper off and lose those higher gusts.
Skies are clearing from north to south and some locales will get to
see the sun for a bit tonight before it sets. With the easterly push
continuing, confidence is not high that we can shed the cloud cover
completely. Expect the clouds to fill back in tonight and most areas
will once again become overcast. Less clouds as you head north,
especially towards the Poconos.
Once good thing is the winds are starting to decrease with every
passing hour. Areas inland will notice the relaxation first and
gradually we will see the gustiness subside tonight. Areas towards
the coast will remain windier as the gradient will take longer to
The easterly flow continues as the high builds down from the north
tonight. Although we continue to dry aloft, we are moist in the
lower levels and the easterly onshore flow will continue to keep
those lower levels moist. We will continue to mention some light
rain or drizzle for tonight, but confine it to the eastern portions
of our forecast area.
Temperatures overnight will be cooler than last night, especially
further north where less cloud cover is expected. Low to middle 40s
across the northern areas with low to middle 50s through much of the
central and southern areas. Extreme south and coastal areas may
remain in the upper 50s overnight.
Short term /6 am Monday morning through 6 PM Monday/...
any lingering light rain or drizzle should end quickly as the dry
air starts to overtake the marine layer across the region. Expect a
much nicer day across the forecast area as skies start to clear out,
with the coast being the last strong hold for clouds.
Winds continue to subside but we may still continue to see some
gusts up to 30 mph, especially towards the coast, but the downward
trend will continue through the day.
Temperatures during the day will warm into the 60s through much of
Long term /Monday night through Sunday/...
long term remains mostly quiet until focus turns to the system
late in the week.
Tuesday and Wednesday...the high slowly slides away from the
region, as a low crossing Canada slides east. The weak cold front
associated with this low and a short wave upper level trough
should propagate through our region on Wednesday. Have kept the
period dry for now, although with the latest model runs, there is
impressive positive pressure advection at the 1.5 pv level,
meaning there is quite a bit of upper level and synoptic scale
lift. However, with low level flow turning northwesterly on
Tuesday, dry air advection will likely preclude any
Thursday through Saturday...next surface high builds in to the
region right on the heals of the Wednesday cold front and is over
the region on Thursday before shifting off shore by Thursday
night. A stronger cold front, and a more significant upper level
short wave trough (compared to the middle week system), should slide
into the region just behind that. The GFS and European model (ecmwf) are in
relatively good agreement of this system being rather progressive
and sweeping through our region on Friday. However, as the
previous shift noted, there will be a transition to more zonal
flow in the upper levels. That, combined with a possible change in
the rossby wave number, and the continued split level flow pattern
(which is notoriously hard to resolve the long term, especially in
transition seasons), means that despite good model agreement, I
still have some uncertainty with the timing of this system.
Therefore, I kept 20 to 30 percent chances of precipitation from Friday
through Saturday, although if the progressive solution holds,
the window of opportunity for precipitation could be half of that, if not
Sunday...could have a secondary surge of colder air approach the
region late in the weekend, although how far south this will get
will be dependent on the upper level flow pattern once again
transitioning to meridional flow. Therefore, at this point, have
not included drastically cooler weather in the forecast, but will
continue to watch.
Aviation /19z Sunday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
As drier air pushes down into the region, we are starting to see
some erosion of the cloud decks from north to south. Conditions have
improved to VFR at kabe and krdg with VFR expected to reach kttn,
kpne, kphl, and kilg over the next few hours. A few breaks may occur
at kmiv and kacy but they are expected to remain MVFR. Ceilings will
creep back down tonight across the region and MVFR to IFR conditions
can be expected.
Winds will be northeast through this afternoon. We should lose the
gustiness tonight but sustained speeds will remain around 10 to 15
For Monday...ceilings will start to rise in the morning and we
should see all locations become VFR through the day. Improvement
will be from north to south. Winds will remain out of the northeast
around 10 to 15 knots. Gusts up to 30 knots toward the coast.
Monday night through Thursday...mostly VFR conditions expected.
Friday...small chance of MVFR ceilings with showers on Friday.
we have dropped the Gale Warning on the northern two ocean zones and
converted it to a Small Craft Advisory, which is in effect until 8pm
Monday. The Small Craft Advisory on the upper Delaware Bay remains
unchanged. The Gale Warning on the southern ocean zones and the
lower Delaware Bay remain unchanged at this time.
Northeast winds will continue through Monday although the gustiness
will gradually subside from north to south. The Gale Warning should
be able to be dropped on Monday, followed with a Small Craft
Advisory through at least Monday evening.
Winds will ramp down fairly quickly. However, the same can not be
said for the seas. Seas will remain elevated through Monday although
we will continue to see a diminishing trend. Seas are currently
around 10 to 15 feet on the ocean and should subside to more of an 7
to 10 feet range by late Monday. Seas on the Bay should also fall
through the day, becoming more in the 1 to 3 or 2 to 4 foot range.
Monday night through Tuesday...winds should gradually drop below
25 knots through this period. Seas however should remain 5 to 10 feet
on the ocean through this period. In the Delaware Bay, winds may
stay below 25 knots through this period.
Wednesday and Thursday...though winds should remain below Small
Craft Advisory conditions, seas should stay elevated on the ocean
waters through at least Wednesday and possibly continuing into
Thursday. This is a result of both the lingering effects of this
weekends system and as wave groups from jaoquin reach our shore.
On the Delaware Bay, winds and seas should stay below Small Craft
Advisory conditions, except right at the mouth of the Bay where
seas just below or near 5 feet are possible.
Friday...winds and seas should stay below Small Craft Advisory
will let the current coastal Flood Warning expire at 6 PM for the New Jersey
and Delaware coast as well as the Delaware Bay. High tide this afternoon has already
passed on the oceanfront but has yet to occur in some of the back
bays and farther up the Delaware Bay toward western Cumberland County and
northern Kent County. On the oceanfront, only the Lewes tidal gauge
came close to moderate but fell just short by a couple of inches.
However, the back bays have the greater risk of moderate flooding
since the prolonged onshore flow has not allowed water from previous
high tide cycles to drain.
Looking into monday's high tide cycles, the etss guidance only
predicts advisory level coastal flooding for Lewes and minor
flooding at Cape May. Ofs guidance is even lower. Regardless, Back
Bay flooding will likely continue into Monday. We will likely issue
a coastal Flood Advisory for Monday for at least our southern
coastal zones when the current warning expires.
On the tidal Delaware, the etss and dbofs guidance continues to run
half a foot too high. Thus applying the same correction factor, this
would result in minor tidal flooding with tonight's high tide cycle
and none on Monday.
We are finding a similar scenario in Chesapeake Bay where cbofs
guidance verified half a foot too high with the concluded high tide
cycle. Here the etss guidance was showing smaller errors and would
take Cambridge to minor, but not our threshold for issuing
advisories with this evening's high tide cycle.
PA...coastal Flood Advisory until midnight EDT tonight for paz070-
New Jersey...coastal Flood Warning until 6 PM EDT this evening for
Wind Advisory until 6 PM EDT this evening for njz024.
Coastal Flood Advisory until midnight EDT tonight for
Delaware...coastal Flood Warning until 6 PM EDT this evening for
Wind Advisory until 6 PM EDT this evening for dez004.
Coastal Flood Advisory until midnight EDT tonight for dez001.
Marine...Gale Warning until 10 am EDT Monday for anz452>455.
Small Craft Advisory until 8 PM EDT Monday for anz450-451.
Small Craft Advisory until 6 am EDT Monday for anz430.
Gale Warning until 6 am EDT Monday for anz431.