Scientific Forecaster Discussion
fxus61 kphi 161554
Area forecast discussion
National Weather Service Mount Holly New Jersey
1154 am EDT Wed Oct 16 2019
low pressure will continue moving slowly east through the Great
Lakes today pushing an occluded front into the mid- Atlantic
region. A secondary low will then develop near the coast by this
afternoon. This second low will rapidly intensify through
tonight as it lifts northeastward toward New England, then
slowly moves through the Canadian Maritimes through Friday while
high pressure approaches from the west. This high will move
across the mid-Atlantic Friday night, then offshore Saturday.
Another frontal system is possible early next week.
Near term /until 6 PM this evening/...
the forecast is pretty much on track so far today. A cold front
is progressing eastward across western Pennsylvania, while an
area of low pressure is beginning to develop across North
Carolina. Rainfall is beginning to spread northward across the
mid Atlantic region as lift and moisture associated a short
wave/vorticity impulse lifts north of developing low and ahead
of the cold front to the west. This low will strengthen as it
moves northward across the Delmarva and across south and eastern
New Jersey this afternoon and this evening. As the low moves
across the area and strengthens, a period of moderate to heavy
rainfall will develop and affect the area. There is some weak
instability, maybe 100-200 j/kg, so a few lightning strikes and
rumbles thunder are possible.
The wind should favor the southeast and south for much of the
day at speeds around 6 to 12 miles per hour. Some gusts of 15 to 20 mph are
possible, especially closer to the coast. Maximum temperatures
are expected to range from the upper 50s in the elevated terrain
of the Poconos to the lower 70s in southern Delaware.
Short term /6 PM this evening through 6 am Thursday/...
the mid level low is forecast to move from southern Ontario
this evening to southwestern New England toward daybreak on
Thursday. It should pull the negative tilt trough over our
region from southwest to northeast between about 9:00 PM and
1:00 am, bringing an end to the rain.
Rainfall totals are expected to range generally from 1.50 to
2.25 inches from the Poconos into northern and central New
Jersey. Rainfall amounts should fall between 0.75 and 1.50
inches in southeastern Pennsylvania, southern New Jersey,
Delaware and northeastern Maryland. The expected amounts should
not cause any widespread flooding problems, so a Flood Watch has
not been issued. However, we are anticipating localized
flooding of roadways and areas of poor drainage, which may be
enhanced as fallen leaves clog some storm drains.
The surface low is forecast to intensify rapidly tonight as it
moves from the waters off New Jersey up into New England. A west
northwest wind is expected to increase to 15 to 25 miles per hour with
gusts of 30 to 40 miles per hour. Wind gusts around 45 miles per hour are possible in
our coastal counties, so the Wind Advisory remains in effect
Low temperatures for tonight are expected to favor the 40s.
Long term /Thursday through Tuesday/...
Thursday through Friday night...
A deep, nearly vertically stacked low will be situated over
central New England to start the period early Thursday. In its
wake a tight pressure gradient will persist over the area
resulting in continuing strong west/northwest winds. Heading through the
day Thursday, the low will slowly drift east across New England
while starting to fill. Strong winds due to the the tight
gradient will continue most of the day. Forecast soundings
indicate vertical mixing up close to 850 mb. Winds in the
925-850 mb layer look to generally be 35-40 knots so still think
we'll see wind gusts upwards of 40 to 50 mph...strongest near
the coast where wind advisories remain in effect. Elsewhere, we
did bump up the wind gusts slightly but still not confident
enough to expand advisory. Otherwise Thursday looks to feature
partly to mostly cloudy skies under the influence of the
system's broad upper low with some scattered showers lingering
over the southern Poconos. Temperatures will be seasonably cool.
Winds diminish Thursday evening as the low continues to weaken
and move eastward into the Canadian Maritimes. It will still
remain on the breezy side though with gusts upwards of 15 to 25
mph. Otherwise, variable cloud cover persists with lows mostly
in the 40s.
For Friday, weakening low continues to drift eastward through
Atlantic Canada while high pressure builds eastward towards the
East Coast. This will result in lighter winds and more sunshine
compared to Thursday but it will still be on the breezy side
with seasonably cool temperatures. The high should build right
over the region Friday night resulting in light winds, clear
skies, and good conditions for radiational cooling. As a result,
lows north of the I- 95 corridor look to make it into the 30s
so frost will be possible.
Saturday through Tuesday...
The weather pattern will remain progressive with a period of
continuing fair weather dominated by high pressure lasting most
of the weekend before the next frontal system affects the region
early next week. Temperatures look to generally be near if not
a little above average through the period.
In terms of the details, high pressure sits over the area early
Saturday before slowly sliding off the coast by late day as the
upper level ridge crests along the East Coast. This will result
in splendid fall conditions with sunshine, light winds, and
seasonable temperatures as highs will be mainly in the 60s.
High pressure with fair weather looks to dominate Saturday
night through at least the first part of Sunday. However by late
day Sunday an area of warm advection precip looks to be setting
up over the southeast Continental U.S. With the northern edge of this possibly
reaching into the mid Atlantic by late day and affecting
southern and western parts of the forecast area. Still some
disagreement on the details between the different forecast
models but given that most of the models keep most of the area
dry the majority of the day we continue to limit pops to slight
chance or lower. So it doesn't look like a washout at this
The best chances for rain with the next system look to occur by
Monday, Monday night, possibly lasting into Tuesday as a low
pressure system moves from the Great Lakes into Ontario. This
will will push a warm front through by late Monday followed by a
cold front by late Tuesday.
Aviation /16z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
This morning...mainly MVFR/IFR ceilings at krdg and kabe.
Generally VFR cloud cover at our other 6 taf sites. Southeast
wind 4 to 8 knots, occasional gusts of 15-20 knots possible.
This afternoon...conditions lowering to IFR with rain, heavy at
times. Localized thunder is possible, but the threat is not
widespread enough to include in the tafs. Southeast wind 6 to 10
knots, occasional gusts of 15-20 knots possible.
Early this evening...MVFR and IFR conditions in rain, heavy at
times. Wind becoming northwest around 10 to 15 knots.
Late this evening and overnight...conditions improving to VFR
with rain ending. West northwest wind 15 to 20 knots with gusts
of 30 to 40 knots.
Thursday...MVFR possible early, improving to VFR through the
day, although periods of MVFR ceilings may last for some areas.
Chance of showers for Abe/rdg. Strong west to northwest wind
gusts of 25-35 knots. -High confidence in winds, moderate
confidence in ceilings.
Thursday night...ceilings may lower to MVFR during the evening
and overnight. Northwest wind gusting 25-30 knots early then
overnight. Diminishing overnight. -High confidence in winds,
moderate confidence in ceilings.
Friday...mainly VFR. Northwest wind gusts 15-25 knots.
-High confidence in winds, moderate confidence in ceilings.
Friday night-Saturday...VFR conditions expected. Wind gusts
drop off during the evening. -High confidence.
a southeast wind around 15 to 20 knots is expected for today.
Gusts near 25 knots, so a Small Craft Advisory remains in
Low pressure is forecast to pass off the coasts of Delaware and
New Jersey this evening and the wind should become west
northwest in its wake. Wind speeds should increase around 30
knots with gusts near 40 knots. As a result, the Gale Warning
remain in effect for tonight.
Thursday-Thursday night...Gale Warning remains in effect.
Conditions lower below gale force late Thursday night.
Friday...Small Craft Advisory conditions early, before lowering
through the day..
Friday night-Saturday...conditions expected to be below
with the developing low near the coast, a period of strong
southeast winds will continue through the afternoon. The two
areas where this may pose a problem are (1) the Eastern Shores
of Chesapeake Bay, with insufficient time to allow for tidal
anomalies to lower after the switchover to west/northwest winds
and (2) the northern New Jersey coast, where winds will switch
to west or northwest last. In these two cases, model guidance is
suggesting that at least spotty minor flooding is possible
around the time of high tide, which for both areas is during the
evening hours. The latest forecast is close to etss guidance,
which verified reasonably well this morning. At this point, no
coastal flood advisories are required for either area; however,
we will continue to monitor observations/trends closely.
New Jersey...Wind Advisory from 10 PM this evening to 6 PM EDT Thursday for
Delaware...Wind Advisory from 10 PM this evening to 6 PM EDT Thursday for
Marine...Small Craft Advisory until 6 PM EDT this evening for anz430-
Gale Warning from 6 PM this evening to 6 am EDT Friday for