Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
912 PM EDT Friday Aug 29 2014
high pressure situated over the northeast will move offshore
tonight...making way for a warm frontal passage Saturday night.
This warm front will become a quasi-stationary boundary near the
Canadian border during the Sunday through Tuesday timeframe...a
trough of low pressure will extend southward from this boundary
to the east of the Appalachians...between a Bermuda high pressure
anchored to the east and slow moving cold front in the Mississippi
Valley. This very weak cold front is projected move through the
region late Tuesday into early Wednesday...followed by Bermuda
high pressure returning to dominance later in the week.
Near term /until 6 am Saturday morning/...
930 PM probable estf: very few adjustments from the 630 PM version.
Upper level trough slides over the region tonight, leaving the
region under clearing skies. The combination of middle and upper
level subsidence, weak on shore/upslope flow, and mostly clear
skies should support patchy fog or stratus development across the
region late. One limiting factor however, is that dew points
remain relatively low. Thus, not anticipating anything widespread
or particularly dense at this time.
Lows could be a bit tricky depending on how much and how quickly
moisture advection takes place tonight. Given how weak the flow is,
think we will be able to have at least a few hours of prime
radiational cooling conditions through late this evening, before
increasing moisture helps to level off the temperature trends.
Short term /6 am Saturday morning through 6 PM Saturday/...
winds will shift to southerly and increase by at least middle morning.
This warm air advection will result in maximum temperatures a few degrees
higher than today, even in spite of any patchy fog that may linger
into the middle morning hours.
Southerly gusts 15 miles per hour during the afternoon.
Long term /Saturday night through Friday/...
hemispheric model analysis shows southeast U.S. Ridging with weak
troughing north of the Great Lakes and middle-west at the start of the
longterm. Better troughing across the western U.S. Moves eastward
eventually carving into the top of the Southeast Ridge by early next
week. The prevailing southwest flow aloft decreases, ultimately
becoming more zonal, as the northern stream of the jet moves to the
north of our region late in the period.
Sunday - Tuesday...slow sagging boundary to the northwest of the region
slows even further and more than likely becomes pseudo-stationary
with strong ridging to our southeast. Middle and upper level flow,
being southwesterly, keep this boundary draped just to our northwest
as warm and moist Gomex air is pumped into the region. Multiple
middle-levels waves, with weak surface troughs, traverse the region
each day providing chances of showers and thunderstorms. The best
chances for convection continues to hone in on the Sunday night into
Monday timeframe as the strongest of the middle-level waves moves
through. Afterwards, higher than normal precipitable water airmass, possibly
exceeding 2 inches, and ample instability each afternoon should
allow for diurnally driven convection. Temperatures and
unfortunately the dewpoints will be on the increase this timeframe
making conditions feel truly like an early August day, in early
Wednesday...low pressure system well to the north of the region
sends a somewhat stronger cold front towards our area. Ridging to
our south should prevent a quick passage, but none-the-less we
currently expect the front to clear or become washed out later in
the day. Still have some low-end chances, mostly north, with this
front though it continues to lose steam running into the building
ridge to our south. We should be drying out north to south by the
afternoon hours with lowering of the dewpoints...temperatures should
still be in the upper-80s.
Thursday - Friday...high pressure continues to build back into our
region with zonal flow aloft. There does not look to be much in the
way of middle-level forcing from any of the passing shortwaves, most of
the energy stays well to our north...we should be dry both days.
Temperatures will venture back down into the normal range with
continued dewpoint lowering.
Aviation /01z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...VFR through at least 06z, with only high cirrus clouds
for most of the region. Light mainly southeast wind.
After 06z...there is a chance that patchy fog could develop. Very
weak onshore flow, subsidence in the middle and upper levels, and
clearing skies will promote fog development. On the other hand,
daytime dewpoints in the 50s indicative of moisture in the lowest
part of the boundary layer...probably the lowest 3000 feet..suggests
not too much low cloud and more of a dewy night as surface dewpoints
edge up to 60f. The highest chance of fog to be near the coast
(kacy and kmiv). If the winds revert to southeasterly, the threat
of fog at kilg would increase thanks to the moist fetch along the
Bay. Given the uncertainties with the moisture advection, have
included visibilities only as low as MVFR.
Conditions should return to VFR by middle morning as southerly winds
Saturday afternoon...VFR scattered-broken at or above 4000 feet. S wind gust near 15
Sunday...VFR. Scattered showers and thunderstorms north and west of
phl. MDT confidence.
Monday - Wednesday...VFR. Scattered showers and thunderstorms possible
everywhere. Low to MDT confidence on precipitation coverage.
wave heights should remain 2 to 4 feet, and winds less than 20kt,
thus conditions should remain below Small Craft Advisory criteria.
Patchy fog may develop Saturday morning on the Delaware Bay,
especially the Upper Bay, but should dissipate by late morning as
Sunday - Wednesday...sub-sca conditions expected across our waters
with high pressure offshore. Cold front will approach Monday and
Tuesday eventually crossing on Wednesday. Winds will back towards the
southwest on Sunday and remain that way through Tuesday. Seas will
increase but remain below Small Craft Advisory at this time.
on facebook we posted a note at 6pm regarding the outlook...Saturday
through much of next week...which is basically a low risk for the
formation of powerful/dangerous rip currents. That risk is moot if
you're a weak swimmer or a tired swimmer and then unexpectedly
are caught in a rip current.
Temperatures will be above normal..at times much above normal..
this Sunday Onward through next Friday. This combined with water
temperatures generally in the 70s will make it favorable for
beachgoers to swim. All good! As long as they swim in the lifeguarded
Why? Because there is about a 1 in 18 million chance of becoming
a rip current casualty under the watchful eyes of the life
guards....much better odds than if you swim on your own where
Rescue potential is not as timely.
This Summer 4 have died along the New Jersey shores due to rip currents
and what was common to all...they swam where lifeguards were not
present...and/or after the hours they were on duty.
The families/friends were unable to Rescue the victims. Many of
US do not realize how powerful the ocean is...and its not the same
swimming in the pool. That and the fact that many of US overestimate
what we can do in the water/swimming skill, can leave a potential
victim in a life threatening situation.
Swim safe and the best way to do that is swim in the presence of
lifeguards while enjoying this fine Labor Day weekend weather.
present weather sensors are ksmq and kfwn are not operating
We dont know when those sensors will be fixed.
near term...drag/Johnson 911