Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
350 PM EST Sat Dec 27 2014
a cold front will cross the area tomorrow, then stall to our south
as a weak low pressure system rides along it Monday and Monday
night. In the wake of the front, a cold air mass slides south and
settles in over the region through New Years Day.
On Friday, a low pressure system could develop over the Southern
Plains and begin lifting northeast towards the region to start the
Near term /until 6 am Sunday morning/...
tranquil night expected as surface ridging continues to move
offshore with US still under its influence for a bit longer. Light
southwesterly winds will continue to usher in a somewhat moister
airmass, ahead of an approaching cold front. Skies will continue to
thicken and lower with time. The position of the front looks to
be just to our west right around sunrise Sunday morning...this is
when we increase probability of precipitation into the likely range. Thermal profiles show
all an liquid ptype for the region as surface temperatures will
only drop into the middle to upper-30s in a lot of places. We could
radiate a bit more towards the New Jersey/Pine barrens, even with
the increasing cloud cover expected...depending on how fast we can
Short term /6 am Sunday morning through 6 PM Sunday/...
cold front will work its way through the region from late morning
through the evening hours. Have increase probability of precipitation to categorical for at
least the southern half of the County Warning Area by Sunday afternoon. Some weak
middle-level energy slides along the front later tomorrow afternoon
which could ultimately slow its departure down a bit. A majority of
the guidance has US drying out from northwest to southeast by late
Sunday evening, just ahead of the better low-level cold air advection kicking in.
There could be some rain/snow mix across our northwest zones late in
the period, depending on how fast we can cool below 850mb and how
much moisture remains. Temperatures will be above normal once again
though several degrees cooler than today with the amount of cloud
cover expected and the rain showers moving in.
Long term /Sunday night through Saturday/...
still a very low confidence forecast in the wake of the cold front
from Sunday night through Tuesday. Most models did agree on one
thing, they are mostly for locations generally along and north of
a philly to Acy line. NAM is by far the wettest and snowiest
outlier showing snow for nearly all of the region. Given that the
trend with the other models has been drier for a few runs now, and
given how much of an outlier the NAM is, forecast favors the GFS
and European model (ecmwf). They both show the front pushing further south before
stalling, with the front now expected to stall or slow by late
Monday afternoon generally from the Florida Panhandle to the SC coast.
As a result, but the time the secondary low deepens and lifts NE
along the front, it is much further out to sea than what previous
Even in Delaware-Maryland-Virginia though, this doesn/T appear to be a major event
as when the moisture is the most abundant, Sunday night, it will
still be warm enough to support rain. By Monday afternoon into
Monday night, colder air has settled in, but so has dry air
advection, limiting moisture availability. So do not expect any
accumulations above an inch.
For much of the rest of the week, the weather looks tranquil,
albeit cold. The Continental polar air mass continues to settle in
over the region. As such many locations northwest of the fall line
will struggle to get above freezing from Tuesday through Friday.
The next thing on the horizon is an intense low, modeled to
be over the Southern Plains by Friday lifting towards the Great
Lakes region. Given how much uncertainty there is early in the
week, and given a large spread in timing and track between the GFS
and ECMWF, it/S risky to hang a hat on either solution. However,
it does appear that the impacts to this region will be a chance
for precipitation, primarily within the warm sector of this low as
it stays northwest of the region (meaning primarily rain). Will have a
chance to refine this once we see how the early week system plays
Aviation /20z Saturday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today - tonight...VFR. Light southwesterly winds, less than 8 knots,
will continue through this evening before decreasing a bit and
backing more towards the west. Altocu deck expected to arrive later
this evening and lower throughout the overnight hours. Confidence:
Sunday...mostly VFR, decreasing to MVFR late in this cycle. Cold
front will slowly approach from the west-northwest by Sunday morning
touching off some rain showers. Conditions should start to
deteriorate into the MVFR range as the showers March towards the
east-southeast. Timing of the showers and MVFR onset could vary by a
couple hours sooner/later. Confidence: mediu
Sunday night...beginning MVFR, and possibly some localized IFR, but
should see conditions improve in the wake of the cold front. At
this point expect conditions to improve to VFR for terminals along
and north of a kacy to kphl line. For kmiv and kilg, MVFR conditions
Monday to Tuesday....mostly VFR conditions expected along and
north of a kacy to kphl line. For kmiv and kilg, there is a chance
for precipitation, some of which could fall as snow. MVFR
conditions are possible with any precipitation.
Tuesday night through Thursday...mostly VFR conditions expected
across the region.
today - Sunday...sub-sca conditions expected. Seas will continue
around 3 feet through late this evening before an increase to around
4 feet is possible...better farther north. Winds will remain
relatively light out of the south-southwest around 10 to maybe 15
knots, though gusts should be kept below 20 knots. Winds back towards
the west later tomorrow evening as a surface cold front moves
Monday through Tuesday...conditions should stay below Small Craft Advisory
thresholds. However, waves of 3 to 4 ft, and wind gusts near or
just above 20kt will be possible especially late Monday night into
Tuesday night through Thursday...sub Small Craft Advisory