Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1105 am EDT Tuesday may 5 2015
a cold front will slowly propagate south over the region today
through Wednesday. In the wake of the front, high pressure will
build over the middle Atlantic region by Thursday and then slides off
shore by the weekend. Another slow moving cold front is possible
early next week.
Near term /until 6 PM this evening/...
no major changes to the overall forecast so far. The cold front
has made its way halfway through the area this morning, and will
continue to slowly sag southward. Overall dry conditions will
continue into the early afternoon, but an area of showers
associated with the first of several short wave/vorticity impulses
is progressing eastward through central Pennsylvania. These
showers may weaken some as they continue eastward, but as a second
vorticity impulse approaches later this afternoon, showers and a
few thunderstorms may redevelop and increase in coverage through
the afternoon, especially as they interact with daytime
The steering flow aloft is rather weak and there is still some
dry air to overcome in the sub-cloud layer...pseudo-inverted v
feature. This would generate some enhanced wind gusts and a slow
moving heavy rain producer.
Temperatures this afternoon will be a tad cooler than they were on
Monday given the increase in cloud cover and less thermal advection
and shallower vertical mixing expected...still well above normal for
Short term /6 PM this evening through 6 am Wednesday/...
on going shower/convective activity will continue through the
overnight hours, though most of the lift should be occurring to our
north-northwest where a passing mesoscale convective vortex/mesoscale convective system feature moves into lower New
York state...the complex currently over the Upper Middle-west states. A
better shot of rain may occur across our northern zones depending on
the aforementioned feature but we cap probability of precipitation at high end chance for
the time being given the uncertainty of its southward progression.
Skies will remain mostly cloudy/overcast tonight with the stalling
cold front across our southern zones. Winds will become light and
variable on either side of the front. Temperatures will drop into
the middle-50s in a lot of places, still well above average.
Long term /Wednesday through Monday/...
Wednesday...cold front should still be slowly moving through the
region tomorrow. Although by tomorrow morning, frontolysis should
begin. Even so, should remain enough isentropic lift and
instability for lingering showers, and over Delaware-Maryland-Virginia (where cape
values are above 500 j/kg), thunderstorms. By Wednesday night
however, should see large scale subsidence as both a surface high
builds in and an upper level ridge approaches from the west.
Therefore, expect Wednesday night to be dry.
Thursday through Friday...surface high and upper level ridge
should remain the main influencing features for our region through
this time...leading to dry conditions and a warming trend. Still
keeping an eye on the low off the coast of the southeastern U.S.
Through this time, but there is good model agreement that it will
remain nearly stationary through this time, which would be
reasonable given the overall pattern. Thus, this still seems to
have little impact for our region.
Saturday through Tuesday...some question as to how quickly the
upper level trough will slide east. GFS shows a far more
progressive solution as compared to the European model (ecmwf) and CMC. Given a
low rossby wave number, and the relatively slow moving lows (both
off the southeast coast and in the desert sw), suspect the slower
solution is the way to go. In the wake of the high, another very
slow cold front should move in. It is unlikely the front will make
significant progress south so long as the ridge remains over the
region. Thus kept most of the region dry Saturday, aside from a
small chance of storms across the higher terrain during the day.
Then, begin increasing probability of precipitation Sunday into Monday.
Aviation /15z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Today...mostly VFR. Some shower activity with isolated thunder is
possible this afternoon at most of the terminals. Acy/miv may have
a better chance of thunder with seabreeze advancement. Winds will
be out of the south-southwest before veering towards the west
Tonight...mostly VFR. Continued shower threat tonight with light and
variable winds. Better chance for MVFR or lower showers exists north
Wednesday...lingering showers and thunderstorms possible. MVFR
expected with any precipitation...otherwise VFR conditions
Wednesday night through Friday night...VFR conditions expected.
Saturday...mostly VFR conditions expected. There is a small chance
of thunderstorms for krdg and kabe.
today - tonight...sub-sca conditions expected. Seas will remain
around 4 feet today and tonight as a slow sagging cold front stalls
across the waters tonight. Winds will veer from the south-southwest
today towards the west tonight but remain light.
Wednesday through Saturday...winds and seas are expected to remain
below Small Craft Advisory criteria.