Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
948 am EDT Friday Mar 14 2014
brief shot of high pressure today and tonight before a weak cold
front passes through early Saturday morning. Another cold front is
expected late Saturday night into Sunday morning setting the stage
for a possible low pressure system to skirt close to our region on
Monday. High pressure quickly fills back in for Tuesday while
another low pressure moves Wednesday into Thursday.
Near term /until 6 PM this evening/...
with low level southerly flow developing, should see a significant
recovery of temperatures back into the 40s and 50s for highs, which
is right around normal for this time of the year. Initially, expect
winds to be relatively light, but wind speeds will increase after
18z as the approaching low from the Great Lakes region will result
in an increasing pressure gradient for US. With no onshore flow,
however, expect only minimal recovery in the dew point temperatures
through the day today. Cloud cover has been persistent this
morning across the entire County Warning Area...but these clouds are still
expected to erode away as the day wears on.
Short term /6 PM this evening through 6 am Saturday/...
the main focus through this period remains the low that will lift NE
out of the Great Lakes region. Despite the still relatively tight
pressure gradient, winds should decouple overnight, at least over
land. There is some modest positive pressure advection at the
tropopause over the Poconos and northwest New Jersey between 06 and 12z Sat. Not
surprisingly, NAM and the GFS show quantitative precipitation forecast for the northern half of our
County Warning Area through this period. There are two main limitations to
widespread precipitation with this feature however. First, the
trough looks to just clip our northern sections. Second, as
mentioned in the near term, there is only limited opportunity for
dewpoints to recover between now and then. Thus, expect that
initially as the trough approaches, it will be mostly virga, until
that starts to result in moistening of the low levels. However, the
low level flow is conducive to some orographic enhancement in the
Poconos. Thus increased probability of precipitation in the Poconos, but kept probability of precipitation near or
below MOS for the rest of the region.
Long term /Saturday through Thursday/...
the weakening cold front will be pushing through at the start of the
longterm period. Still continue to see the highest probability of precipitation across our
northern zones with next to nothing across the southern half. Quantitative precipitation forecast is
on the order of a couple hundredths and a mix of rain/snow is
possible in the higher terrain, otherwise all liquid is expected.
Stiff westerly downsloping winds develop behind this front and the
skies should begin to scatter out a bit allowing for temperatures to
jump a bit higher than the stat guidance is showing...we edged
A second cold front will then push through later Saturday night into
Sunday morning and bring with it a colder airmass, but we should
remain dry with this passage as all the energy remains well to the
north of the region. This is when things become more interesting
with the development of a low pressure along the frontal boundary
across the deep south late on Sunday.
What was originally a split flow becomes more amplified with a
building ridge across the western United States making for a better
defined trough downstream and northwest Pacific energy diving down
deep into the southern U.S. Depending on how strong this energy
eventually becomes/is and how fast it phases with its southern
stream counterpart would ultimately dictate where the middle-level
troughing sharpens/deepens and where the surface low would track.
The past several days have kept a majority of the middle-level energy
to our south though a northward trend has been seen with the past
several runs of the Middle-Range guidance. The ensembles members off
both the gefs and ec have shown the most noise/spread to the north
of the surface feature giving more credence to a northward jog. The
northward jog is two fold with more moisture traversing the region
and also a tighter thermal gradient across at least our southern
zones at this point in time.
For the most part the northern half of the region will be cold
enough for all frozen precipitation with a cold dome in place. Down
south, if the north trend continues, would see a changeover to snow
as the system moves further away from the region. Guidance is
showing a warmer layer around 800-850mb which could move pretty far
northwest giving way to more of a mix-bag across the southern half
which would greatly cut-down on the potential for an accumulating
At this stage in the game, confidence is increasing of a coastal low
affecting the region late Sunday night through a better portion of
Monday...the signals are there for it. Specifics about p-type and
accumulation amounts still need to be ironed out but we have plenty of time
for that as the northwest Pacific energy has yet to come
onshore...just a matter of time.
A brief respite on Tuesday as the aforementioned system pulls
further away and weak ridging moves in behind it. The next system,
not handled very well at this point on the models, looks to remain
to our northwest as its associated fronts affect US late Wednesday
through Thursday. We keep the chance probability of precipitation for this timeframe.
Temperature-wise, with the exception of Saturday, we should remain
below normal through the period with East Coast troughing in place.
What a way to start the Spring.
Aviation /14z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
VFR conditions will continue through the day today. Winds will shift
to southerly or south southwesterly and increase through the morning
in response to an approaching low in the Great Lakes region.
After 00z, winds should once again decrease to near 10kt. Mostly VFR
conditions are expected. There is a small threat...30 percent or
less...for rain showers after 06z primarily at kabe, kttn, and locations
further north. MVFR ceilings are possible under any of these
Saturday...mostly VFR. Cold front will cross the region on Saturday
with sub-VFR possible in rain/snow showers early north of rdg/Abe.
Sunday night-Monday...MVFR/IFR conditions possible with areas of
snow and rain...better chances for all snow are phl and northwest. Gusty
NE winds 20-25 knots.
currently seeing a lull in the wind speeds, but winds are expected
to increase once again to Small Craft Advisory conditions early this afternoon. Winds
will stay up overnight tonight.
Saturday - Sunday...sub-sca conditions expected by Saturday afternoon. Winds
shift back towards the west-northwest behind a cold front later on
Sunday night-Monday...return to Small Craft Advisory conditions
possible with possible coastal low. Gale force winds are possible on
Monday with the upcoming system.
Tuesday...lingering Small Craft Advisory-conditions possible.
though not as windy as yesterday, it will still be breezy and very
dry across Delaware-Maryland-Virginia and southern New Jersey today. Minimum relative humidity
values will be 23 to 33 percent in this region, and winds will be 10
to 20 miles per hour with gusts up to 30 miles per hour. Fuel moisture remains a bit high
thanks to recent precipitation, so will cover the enhanced fire
weather threat with an Special Weather Statement for now.
Marine...Small Craft Advisory from 1 PM this afternoon to 3 PM EDT
Saturday for anz450>455.