Scientific Forecaster Discussion
fxus61 kphi 162059
Area forecast discussion
National Weather Service Mount Holly New Jersey
359 PM EST Sat Nov 16 2019
high pressure north of the area will move offshore on Sunday
while south of the area a deepening low will lift slowly
northeastward off the Carolina coast. By Tuesday morning, the
low should progress northeast to the Canadian Maritimes and
surface high pressure will build into the southeastern US
for the middle of next week. This high pressure slides offshore
on Thursday and a Great Lakes low and associated cold front
will likely impact the area late next week.
Near term /through tonight/...
Overall, not a significant order of change in the near term
forecast with a relatively quiet Saturday. Dry air behind the
weak cold front that moved through the region last night
continues to keep US sunny, though there is certainly a bite of
winter in the air as afternoon temperatures will only make it
into the upper 30s to low 40s for most of the area. As the
coastal storm continues to develop off the Carolina coast, the
pressure gradient will continue to increase against a strong
1038 mb surface high across the northeast. This is enhancing the
brisk northeasterly winds, which will continue to gust from 20
to 30 mph, making it feel a bit colder with wind chills
remaining below freezing through the afternoon and evening.
Winds are even stronger over the open waters and along the immediate
coast. Lewes has been gusting to gale force this afternoon, with a
few locations along the southern New Jersey coast also beginning to
gust near gale force. A Wind Advisory remains in effect for coastal
Sussex, Cape May, and Atlantic counties through the remainder of the
day and into Sunday for the potential for gusts exceeding 46 mph.
Winds will continue after sunset with only a slight taper downward;
given the synoptic nature of the winds with an increasing pressure
gradient, they are not expected to decouple as was the case the past
few nights. These along with increasing cloud cover, especially
along and south of the Atlantic City expressway.
Short term /Sunday/...
By Sunday morning, the aforementioned coastal low will be much
better organized as it becomes vertically stacked with the
closed 500 mb low moving overhead of the surface low. Gradual
intensification of the low is forecast as it moves northeastward
over the Atlantic with a minimum pressure dropping to somewhere
around 990 mb or so by Monday morning. There is also some
indication that some form of a surface trough or norlun trough
may begin to form tomorrow morning as the surface low moves
closer towards the mid- Atlantic, allowing for an earlier onset
of rain and rain showers across the New Jersey coast. The ec
appears to indicate this potential a little more strongly than
the GFS at this point. This isn't expected to have much impact
on the forecast, but did adjust the pops accordingly. All in
all, rain will push northward Sunday, affecting Delmarva and the
immediate coast first, but eventually overspreading much of the
forecast area by 1-3 PM, especially along and east of the I-95
corridor given the track of the low. Total rainfall amounts
Sunday will be on the lighter side with most places only seeing
up to a quarter to maybe a half of an inch along the immediate
coast if rain moves in early enough.
Winds will remain similar, if not stronger than today with gusty
northeast winds from 25 to 30 mph possible, and higher gusts from 45
to 50 mph in the Wind Advisory areas near and along the coast. With
highs in the low to mid 40s, this will lead to another chilly day,
especially once the rain begins.
Another factor with this storm will be the freezing rain potential.
While not a widespread concern, forecast soundings suggest light
freezing rain is possible across Sussex County, New Jersey and into the
southern Poconos. Timing of this will be highly dependent on
how fast a vort Max moving in from the west amplifies the longer
wave synoptic trough associated with the coastal storm. The
very dry air as we have seen today will also be a factor, with
rain holding off until Sunday night in these areas as the lower
atmosphere moistens. Evaporative cooling associated with such
process may also aid in cooling the column. More on this in the
long term discussion.
Long term /Sunday night through Saturday/...
Overview: the coastal storm that has been impacting the area
this weekend will slowly progress east of the area Sunday night
into Monday, before finally completely clearing the area
Tuesday morning. A couple of northern-branch shortwaves will
pass through the area on the backside of this system, with the
first arriving Monday night, and the second Tuesday night into
Wednesday morning. High pressure builds into the southeastern US
mid-week, however this looks to be short-lived as another
shortwave and associated surface low/fronts will approach the
Sunday night through Tuesday morning... unfortunately overall
confidence regarding precipitation potential, amounts, and (to
an extent) type remain lower than usual over this period. The
first chance of precipitation will be with some warm-advective
precipitation wrapping around the north-side of the approaching
coastal low Sunday night into Monday morning. Guidance is not
very generous with the inland penetration of this precipitation
and therefore generally went with quantitative precipitation forecast amounts around 1-2 tenths
near the coast with amounts only in the hundredths further
inland (with some areas potentially not receiving any
precipitation at all. The energy associated with the kicker
shortwave approaching the area Monday afternoon into Monday
night does look more robust with the 12z cycle so raised
pops/quantitative precipitation forecast (mainly over the northwest) in that time period
(although dry advection will temper some of the precipitation
There still looks to be some conditional (on precipitation
occurring) freezing rain potential for areas primarily north of I-80
(with a more outside chance between I-78 and I-80) Monday
morning. At this time have a few hundredths of ice accumulation
primarily in the Poconos and Sussex County NJ, but confidence
is too low regarding pops to initiate any winter weather
headlines at this time. Can't rule out some freezing rain
potential in these areas Monday night/Tuesday morning as well,
but confidence remains low.
Tuesday through Thursday... a relatively quiet period should
prevail through the mid-week with maxes generally running within
a few degrees of climo (generally upper 40s to lower 50s),
although temperatures will likely warm up a bit on Thursday as
southerly flow increases. Can't rule out some light
precipitation Wednesday morning in association with a mid-lvl
wave, but at this point this looks sufficiently moisture-starved
to not be much of a concern.
Thursday night through Saturday... the next storm system
approaches the area towards the end of next week, but the
details remain uncertain regarding timing the associated cold
front/precipitation. Much will depend upon the interaction of
various northern branch disturbances and energy associated with cutoff
lows over the Desert Southwest. Consequently broadbrushed chc.
Pops and used a simple p-type algorithm based on temperatures
for the Friday/Saturday am period.
Aviation /20z Saturday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
This evening and tonight...VFR with mostly clear skies through the
remainder of the day. Northeast winds from 10 to 15 knots and gusts
from 25 to 30 knots. Stronger gusts to 35 knots possible along the
immediate coast. High clouds will begin to overspread the region
from the south, however, VFR cigs are expected through 10z at the
philly terminals. MVFR cigs possible at Acy and eventually miv after
00z. High confidence in the winds, medium confidence in cigs.
Sunday...VFR conditions to drop to MVFR after 10z with all locations
likely to drop to MVFR by 18z, with the exception of Abe and ridge.
Strong northeasterly winds from 10 to 15 knots and gusts to 25
knots. Stronger winds from 20 to 30 knots and gusts to 40 knots
likely near and along the immediate coast. Rain will move into the
region from southeast to northwest, overspreading the philly
terminals near or around 20z. High confidence in winds, medium
confidence regarding cigs and precipitation timing.
Sunday night...MVFR with possible IFR conditions as rain falls
across some of the region, with highest chances at miv and Acy.
Winds remain gusty 20-30 knots, shifting from northeast early to
northerly by Monday am. Moderate confidence in flight categories,
high confidence in winds.
Monday...some improvement possible to VFR during the day on
Monday, but can't rule out continued periods of rain and sub-VFR
ceilings. Northwest winds around 10 kts, with gusts to 20 kts
possible at kacy. Moderate confidence in ceilings, high
confidence in winds.
Monday night...may see some light rain (possibly mixed
precipitation north of the terminals) and sub-VFR conditions.
West to northwest winds up to 10 kt. Confidence in
precipitation/ceilings is below average, but in winds is above
Tuesday and Tuesday night...mainly VFR with west to northwest winds
5 to 10 kt. Some higher gusts are possible during the day.
Wednesday...mainly VFR with northwest winds 10 to 15 kt with higher
gusts. Moderate confidence.
Thursday...mainly VFR although some precipitation could approach
the western terminals late. Westerly winds shifting to the
southwest around 5-10kts Thursday afternoon.
this evening and tonight... gale force wind gusts with northeasterly
winds up to 40 knots to continue through the overnight. A Gale
Warning remains in effect for all the Atlantic zones along with the
southern Delaware Bay. A Small Craft Advisory remains in effect for
the northern Delaware Bay through the overnight an into Sunday with
northeasterly winds gusting to 30 knots. Seas building from 8 to 12
feet, especially for the southern Atlantic zones and from 3 to 5
feet across the Delaware Bay.
Sunday...Gale Warning continues for the Atlantic zones and southern
Delaware Bay with northeasterly winds gusting to 40 knots. A Small
Craft Advisory remains in effect through the day for the northern
Delaware Bay with northeasterly winds gusting to 35 knots. Seas
building from 9 to 12 feet across all the Atlantic zones and from 3
to 5 feet across the Delaware Bay.
Sunday night/Monday morning... gale-force gusts likely continue,
but begin to decrease into Monday morning, seas remain elevated
at over 10 ft on the Atlantic waters.
Monday afternoon into Monday night... northerly-northwesterly
gusts decrease below gale force by early Monday afternoon, and
then decrease below Small Craft Advisory criteria by Monday night. Seas generally
8-10 ft Monday during the day, and decreasing to 5-7 ft by
Tuesday and Tuesday night...sub-advisory winds/seas expected.
Wednesday...generally sub-advisory winds/seas expected however,
northwest winds may approach advisory criteria by late
deep low pressure off the southeast and middle Atlantic coasts combined
with high pressure to our north will maintain a strong northeast wind
along the shores of Delaware and New Jersey through Sunday night. The
expected onshore flow will affect five consecutive high tide cycles and
should result in another lengthy period with the threat of tidal
flooding, similar to what occurred back around the 10th through 12th of
We have issued a coastal Flood Warning for moderate flooding on Sunday
and Monday for tidal areas of Delaware and New Jersey. While locations
up and down the Delaware and New Jersey coasts could see moderate
flooding, widespread moderate flooding is most likely to occur from
about Barnegat Inlet south. The daytime high tides will be the higher
of the two daily high tides.
As we get closer to Sunday and Monday, a coastal flood advisory
may be issued for the tidal part of the Delaware River.
Also, minor flooding is possible up into the upper part of Chesapeake
Bay on Sunday and Monday evenings, so an advisory may also become
necessary along the upper Eastern Shore as well.
The strong and persistent onshore wind will likely result in
significant beach erosion along the coasts of New Jersey and
New Jersey...coastal Flood Warning from 8 am Sunday to 5 PM EST Monday for
Wind Advisory until 6 PM EST Sunday for njz024-025.
Coastal Flood Warning from 10 am Sunday to 6 PM EST Monday for
Delaware...coastal Flood Warning from 8 am Sunday to 5 PM EST Monday for
Wind Advisory until 6 PM EST Sunday for dez004.
Coastal Flood Warning from 10 am Sunday to 6 PM EST Monday for
Marine...Gale Warning until 6 am EST Monday for anz431-450>455.
Small Craft Advisory until 6 am EST Monday for anz430.