Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
946 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/...
clouds are expected to fill back in tonight and most areas will
once again become mostly cloudy to overcast. Less clouds as you
head north, especially towards the Poconos.
Winds across most inland areas of northern New Jersey and eastern
Pennsylvania are diminishing and losing their gusts, which should
continue into the night as the pressure gradient weakens. Areas
towards the coast and across the south will remain windier as the
gradient will take longer to weaken there.
There remains some reflectivities on the radar over the ocean this
evening that are moving toward the coast. There is relatively dry
air over land right now, so not sure how far this will move
inland. Lower levels should saturate some overnight, especially
for central/southern New Jersey and Delaware-Maryland-Virginia. We will continue to
mention some light rain or drizzle for tonight, but keep it
confined 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 /02z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy, and surrounding areas.
The lower clouds have cleared our for all sites except Acy/miv
this evening and have been replaced by middle-high level clouds.
However, ceilings will creep back down tonight across the region
as the easterly flow continues and lower levels saturate, and
MVFR conditions can be expected.
Northeast winds will continue through the night. Gusts should
diminish most areas except across the south and closer to the
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 with occasional gusts around 20 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.
the Small Craft Advisory for the northern waters and the upper
Delaware Bay remains in place. The Gale Warning on the southern
ocean zones and the lower Delaware Bay remain unchanged at this
time as well.
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 Joaquin 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
on the tidal Delaware, the coastal Flood Advisory was cancelled.
Tidal levels at the Reedy Point and Philadelphia gauges reached
minor flood stage but not 1 to 2 tenths of a feet below advisory
threshold. No coastal flooding is expected there on Monday.
Additionally, a coastal Flood Advisory was issued for Queen
Anne's, Caroline and Talbot counties in Maryland along the Eastern Shore
of the Chesapeake Bay for this evening's high tide. At 930 PM,
Cambridge was at 3.7 feet MLLW, which is only 0.1 feet below advisory.
High tide is at 1046 PM, so it should reach advisory criteria.
All coastal flooding warnings were expired at 6 PM. A coastal
Flood Advisory was then issued for the coastal Atlantic counties
in extreme southern New Jersey and Delaware as well as the Delaware Bay through the
Monday afternoon high tide. 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. Opted to not extend the advisory farther northward
up the Jersey Shore with guidance showing the surge and anomalies
near zero on Monday for Atlantic City and Sandy Hook. However,
there will likely be spotty minor coastal flooding in the back
New Jersey...coastal Flood Advisory until 7 PM EDT Monday for njz021-023-
Delaware...coastal Flood Advisory until 7 PM EDT Monday for dez002>004.
Maryland...coastal Flood Advisory until 2 am EDT Monday for mdz015-019-
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.