Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
358 am EDT Monday Aug 3 2015
a cold front from the Great Lakes will slowly approach from the
northwest today, eventually tracking through our region into early
Tuesday. This front is forecast to stall just south of our area
through the middle to end of the week with waves of low pressure
moving along it. The final wave of low pressure looks to pass
offshore Saturday with high pressure from eastern Canada
possibly building southward on Sunday.
Near term /until 6 PM this evening/...
mostly a dry day is expected as airmass modification continues.
Deeper mixing today will keep the surface dewpoints in check, for
the most part, so not expecting sweltering conditions with
temperatures a few degrees warmer than the past couple days.
Strengthening southerly winds, with gusts upwards of 25 mph, will
help to usher in more moisture but without an appreciable trigger,
even as MLCAPES climb towards 1500j/kg this afternoon, should keep
US mostly storm free until later this evening. Weakening cold
frontal passage should trigger a line of storms to our west by middle-
afternoon, so it basically becomes a race against the better surface
heating and if the storms can speed up. Any storms that do move into
our region will have a decent amount of shear in place, oriented
perpendicular to the frontal convergence zone, which would allow for
better organization and possible bowing segments...have gusty winds
added into the grids for late this evening. It is possible that pre-
frontal/thermal trough develops well ahead of the cold front which
could be our main trigger during the middle-afternoon hours so we could
be a tad slow with our chance probability of precipitation today.
Short term /6 PM this evening through 6 am Tuesday/...
cold front will continue to slip through the region but begin to
slow its forward progress as the flow aloft turns more parallel with
time...it should stall across our southern zones late tonight. Not
quite sure how quickly we can dry out west to east behind the front
since we really do not see much of an airmass change. A middle-level
impulse, just behind the surface front, looks to push through which
may either continue the on-going convection in the eastern portions
of our County Warning Area or generate a few trailing showers heading into Delaware-Maryland-Virginia
after midnight tonight.
Long term /Tuesday through Sunday/...
an active and unsettled pattern is anticipated through the long term
period as a frontal boundary will be stalling just south of our
forecast area with a few waves of low pressure expected to develop
and move along it through the end of the week and perhaps into the
early part of the upcoming weekend.
For Tuesday, a cold front is forecast to be tracking through our
area early in the day, eventually stalling out to our south and east
into Tuesday night. The presence of the stalling front near/across
our area will keep some slight chance to low chance probability of precipitation for
showers/thunderstorms in the forecast for Tuesday, especially for eastern
and southern locations, including eastern/southern New Jersey and into the
Delaware-Maryland-Virginia. Meanwhile for the I-95 corridor and areas north and west,
the convective potential looks to be minimal with ensuing cold air advection and
falling dewpoints in the wake of the cold front passage.
Despite the stalled frontal boundary lingering just to our south,
Wednesday looks to be a precipitation-free day at this time, as a wave of
low pressure does not look to develop along the boundary until more
during the day Thursday. In addition, as noted by the previous
shift, convective temperatures are not forecast to be reached during the
daytime Wednesday, and drier low-level air will still be in place
with dewpoints across much of the region in the 50s to low 60s.
Maximum temperatures look to be right around early August averages with
highs mainly in the middle to upper 80s across the area.
For the remainder of the long term from Thursday through Saturday,
with the stalled frontal boundary just off to our south and a few
waves of low pressure potentially tracking along it, there will be
higher chances for scattered shower/tstorm activity, along with the
potential for heavy rain. We carry high chance probability of precipitation overall through
most of this period; although, there are still noteable model
differences with regards to the timing and track of the developing
waves of low pressure. So while this two to three day period looks
to have a higher probability for increased shower/tstorm activity,
there is too much uncertainty at this extended range to narrow down
the timing and/or areal extent of convective activity and associated
areas of heavy rain. We will continue to highlight this potential,
though, in our hazardous weather outlook. Some improvement may be
expected into the upcoming weekend, especially from late Saturday
into Sunday, as the last wave of low pressure travels east and out
to sea, with an area of high pressure across eastern Canada building
southward toward the northeast to northern middle Atlantic during
Aviation /08z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today...VFR. Southerly winds around 8 to 10 knots by later this
morning with some gusts close to 20 knots through the early evening
hours. Stratocu around 5kft this afternoon. Most of the showery
activity should hold off until late evening...mostly northwest of Abe.
Tonight...VFR. Showers and thunderstorms possible but scattered
coverage does not allow inclusion in tafs at this time. We will lose
the gusts as winds remains light out of the south.
Tuesday...mostly VFR conditions. Isolated to perhaps scattered
showers/thunderstorms are possible, especially eastern terminals.
Wednesday...mainly VFR conditions.
Thursday and Friday...MVFR conditions during showers/tstorms, with
some IFR conditions possible. While confidence of occurrence is
increasing, timing confidence remains low.
Small Craft Advisory conditions look to commence later this afternoon with tightening
pressure gradient and strengthening southerly flow raising seas
towards 5 feet. Numerous gusts upwards of 25 knots are expected to
occur ahead of an approaching cold front later tonight.
Tuesday...a Small Craft Advisory will continue for the coastal
waters through Tuesday morning. While wind gusts are expected to
have fallen off by early Tuesday, seas will likely still remain at 5
feet or above through Tuesday morning. Improving conditions with
seas subsiding are expected into Tuesday afternoon.
Wednesday...sub-advisory conditions are expected.
Thursday and Friday...mostly sub-Small Craft Advisory conditions; however, a stalled
front and a wave of low pressure moving along it could enhance seas
and/or winds for the coastal waters, making Small Craft Advisory conditions possible.
there is a moderate risk for the formation of dangerous rip
currents today for the New Jersey shore and the Delaware beaches.
Marine...Small Craft Advisory from 4 PM this afternoon to 10 am EDT
Tuesday for anz450>455.