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000 
FXUS61 KPHI 170231
AFDPHI

Area Forecast Discussion
National Weather Service Mount Holly NJ
931 PM EST Sat Nov 16 2019

.SYNOPSIS...
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 /UNTIL 7 AM SUNDAY MORNING/...
930 PM Update: No significant changes made to the forecast.
Some light rain showers indicated on radar off and on over the 
past few hours. This trend is likely to continue across southern
Delaware and extreme southern NJ through daybreak, so I added a
mention of this in the forecast. Very low dewpoints inland will
continue to rise slowly overnight. Otherwise, the forecast
remains on track at this time.

630 PM Update: No changes made to the forecast with this update. 
Winds have diminished somewhat and gusts have come down away from 
the immediate coastline. A cold and dry night in store for most 
(away from the coast) with a persistent northeast wind around 10 mph 
(higher near the coast) and increasing clouds toward daybreak.

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH 6 PM 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, NJ 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 
area Friday.

Dailies:

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 QPF 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/QPF (mainly over the northwest) in that time period 
(although dry advection will temper some of the precipitation 
potential).

There still looks to be some conditional (on precipitation
occurring) FZRA 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 /03Z SUNDAY THROUGH THURSDAY/...
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY and surrounding areas.

Tonight...Initially VFR with low clouds building from the south
and east through the overnight. MVFR CIGs developing through 
the overnight for MIV and ACY and toward daybreak for the I-95 
corridor terminals. Northeast winds from 10 to 15 knots. Not 
expecting much in the way of gusts until the cloud cover builds,
then gusts of 15-20 knots possible toward daybreak. Stronger 
gusts to 30 knots possible along the immediate coast. High 
confidence in the winds, medium confidence in CIGs.

Sunday...Residual VFR conditions to drop to MVFR by daybreak, with 
the exception of ABE and RDG. 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 toward 00Z. High confidence in 
winds, medium confidence regarding CIGs and precipitation
timing.

Outlook... 

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 
average.

Tuesday and Tuesday night...Mainly VFR with west to northwest winds 
5 to 10 kt. Some higher gusts are possible during the day. 
Moderate confidence.

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.

&&

.MARINE...
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. 

Outlook... 

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 SCA criteria by Monday night. Seas generally
8-10 ft Monday during the day, and decreasing to 5-7 ft by
Monday night.

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 
afternoon.

&&

.TIDES/COASTAL FLOODING...
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 
October.

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
Delaware.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...None.
NJ...Coastal Flood Warning from 8 AM Sunday to 5 PM EST Monday for 
     NJZ012>014-020>027.
     Wind Advisory until 6 PM EST Sunday for NJZ024-025.
     Coastal Flood Warning from 10 AM Sunday to 6 PM EST Monday for 
     NJZ016.
DE...Coastal Flood Warning from 8 AM Sunday to 5 PM EST Monday for 
     DEZ002>004.
     Wind Advisory until 6 PM EST Sunday for DEZ004.
     Coastal Flood Warning from 10 AM Sunday to 6 PM EST Monday for 
     DEZ001.
MD...None.
MARINE...Gale Warning until 6 AM EST Monday for ANZ431-450>455.
     Small Craft Advisory until 6 AM EST Monday for ANZ430.

&&

$$
Synopsis...Carr
Near Term...Davis/Staarmann

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