Scientific Forecaster Discussion
fxus61 kphi 132043
Area forecast discussion
National Weather Service Mount Holly New Jersey
343 PM EST Wed Nov 13 2019
Arctic high pressure will continue to build across our region
through tonight, then it shifts offshore during Thursday. A
cold front will move through later Friday, then high pressure
builds into our area from the northwest and north later Saturday
and Sunday. An ocean storm develops off the southeast coast
Friday night and slowly moves northeastward over the weekend
with it currently looking to remain to the south and east of our
region, then another storm may develop off the Carolina coast
early next week.
Near term /until 6 am Thursday morning/...
high pressure will crest across NE PA and nrn New Jersey this evening
and then start to move away overnight. Clear skies and light
winds are expected with nearly ideal radiational cooling.
Therefore, lows will once again be well below normal with
widespread teens and low 20s again expected. There is a good
chance that some records lows will again occur for 11/14. We'll
keep the records listed below for reference.
Short term /6 am Thursday morning through 6 PM Thursday/...
high pressure that has brought all the cold air to the region will
be on its way out, bring over New England, Thursday morning. A
return flow behind the high will kick in during the day and the well
below normal temperatures of Wednesday will be gone. Still, highs on
Thursday will still be about 10 degrees below normal with readings
topping out in the mid/upper 40s across the S/east areas and low 40s
N/W. These readings are about 10 degrees higher than Wed.
Overall, mostly sunny skies are expected but there will be some
CI/cs clouds around occasionally. The NAM was indicating some low
clouds across Delmarva and srn New Jersey during the morning with the flow
off the ocean beginning there first, but I have deemphasized this
for now with the dry air and ridge remaining the dominant factors.
Light winds early will become S/southeast by late morning and then SW by
afternoon. Speeds will increase to around 10 mph by afternoon.
Long term /Thursday night through Wednesday/...
summary...some moderation of the cold and dry air mass expected
into the day Friday. A colder air mass then arrives for
Saturday into Sunday before milder air should overtake our area
early next week. A couple of storm systems however look to track
offshore over the weekend and through early next week.
Synoptic overview...a positively tilted upper-level trough from the
Great Lakes to the Central Plains Thursday will shift eastward into
Friday. The northern part of this feature looks to get absorbed into
a much stronger trough/closed low sliding southeastward from near
Hudson Bay Canada. Meanwhile, energy within a southern stream is
forecast to close off across the Gulf Coast states Friday then it
gradually shifts off the southeast coast over the weekend. This
system aloft is forecast to develop surface low pressure off the
southeast coast late Friday and it slowly shifts northeastward over
the weekend into early next week. An upstream system should kick the
lead short wave along but reinforce the surface boundary along the
Gulf Stream. This however may develop another surface low off the
North Carolina coast, as it also lifts northeastward in advance of
an amplifying upper-level trough.
For Thursday night and Friday...a short wave trough is forecast
to slide eastward from the Great Lakes region Thursday to New
England Thursday night, with a clipper system at the surface
tagging along with it. This will toss a weak cold front across
our area mainly Friday night. The main warm air advection and
therefore lift is focused well to our north therefore no
precipitation is expected with it as of now. However, energy
diving across the southern states Thursday is forecast to close
off as is nears the southeast coast. This will induce surface
low pressure development along a lingering baroclinic zone. Some
energy and forcing ahead of this feature may try to produce
some light showers Thursday night into Friday across southeastern
New Jersey and portions of Delmarva. This may be focused near a
zone of increasing warm air advection, a low- level jet and
some convergence near 850 mb. This is less certain though given
weaker forcing this far north, with the main focus farther south
closer to the closed low and developing surface low. For now,
kept some slight chance to chance pops in for portions of the
aforementioned area. The thermal profiles should be warming
enough for mainly rain, although this may have to battle some
lingering mid to low level dry air. Given enough warm air
advection, most places should warm to around 50f Friday
afternoon despite more cloud cover.
For Saturday through Tuesday...the model guidance is in pretty good
agreement with the large scale features during this time frame.
There are two features of note, both of which slide across the
southern states. An initial closed low exits off the southeast coast
later in the weekend then may open up some as it lifts east-
northeast and takes surface low pressure with it. While the bulk of
this system should remain far enough offshore to keep much of the
precipitation out of our area, some periods rain or drizzle
cannot be ruled on at some point over the weekend. Our area
though may remain protected enough from surface high pressure
that may maintain itself near northern New England with an
extension southwestward. This however will result in a tight
pressure gradient as surface low pressure tracks offshore, and
therefore a gusty northeasterly wind is expected especially
closer to the coast. This surface high will result in another
shot of cold air Saturday into Sunday, then some moderating
occurs next week however the onshore flow will probably offset
this some especially closer to the coast and if thicker cloud
cover and some rain occurs. A secondary strong piece of energy
may induce another surface low off the Carolina coast during
early next week and that will also track northeastward ahead of
a much more amplified upper-level trough. While the guidance
agrees with the overall setup, the details are less certain and
therefore generally blended the 00z wpc guidance in with
Aviation /21z Wednesday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...VFR. Only some high level clouds expected. Light northwest winds.
Thursday...VFR. Some low clouds possible moving in across srn New Jersey/Delaware
during the morning. Light winds becoming S/SW 5 to 10 knots by
Thursday night...lowering VFR with MVFR ceilings possible at
Acy and miv. A few rain showers possible near Acy and miv.
Light and variable winds. Moderate confidence, however low
confidence regarding any MVFR ceilings.
Friday and Saturday...mainly VFR ceilings. Light and variable winds
becoming northwest around 10 knots during Friday then turning
northerly Friday night, then northeast 10-15 knots with gusts to
around 25 knots Saturday (strongest at acy). Moderate confidence.
Sunday...areas of MVFR ceilings possible especially closer to the
coast with a chance of some rain. Northeast winds 10-15 knots with
gusts to around 25 knots (strongest at Acy to miv). Low confidence.
we will cancel the Small Craft Advisory flag with this afternoon coastal waters forecast issuance. Northwest
winds will continue to decrease overnight. Winds will veer to north then
NE early, then go east to southeast late. Winds speeds will drop to 5 to 10
knots late. Seas which are close to 4 ft this evening will diminish
to around 2 ft late. Fair weather.
The high will move towards New England, so the return southeast to S flow
will continue over the waters during the morning and then become SW
by afternoon. Speeds will slowly increase to 10 knots late. Seas
mostly 2 to 3 ft. Fair weather.
Thursday night through Friday...the conditions are anticipated
to be below Small Craft Advisory criteria much of the time,
however winds increase Friday night with an advisory probable
(gusts could near gale force closer to daybreak saturday).
Saturday and Sunday...a period of northeast gale force wind gusts
are expected with rough seas.
low temperature records were set for yesterday (11/12) and
also for today (11/13). Six rer's were sent earlier this morning
for cold lows today. It's possible that more may be set tonight
since it will remain bitterly cold through Thursday. Here are
the record low temperatures for today and thursday:
Climate sitenov 13
allentown18 in 1996 (tied this morning)
Atlantic city22 in 2001, 1996, and 1995 (new record = 21)
atl. City Marina 24 in 1920
georgetown21 in 1996
mount pocono12 in 1911 (tied this morning)
philadelphia24 in 1996 (new record this morning = 23)
reading21 in 1976 (new record this morning = 19)
Trenton 23 in 1920, 1911 (new record this morning = 21)
wilmington18 in 1911
Climate sitenov 14
allentown17 in 1986
Atlantic city15 in 1986
atl. City Marina 23 in 1874
georgetown22 in 1986, 1950
Mount Pocono 5 in 1905
philadelphia19 in 1986
reading16 in 1986
Trenton 20 in 1905
Wilmington 20 in 1986, 1911