Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
339 am EDT Sat Sep 5 2015
high pressure will build into our area from the north today, then
become mostly centered offshore Sunday and Monday. A cold front is
forecast to approach our region late Wednesday, then stall nearby
Thursday into Friday.
Near term /until 6 PM this evening/...
high pressure was centered over northern New England this morning.
The center of the high will slide to the south today and it is
expected to reach the waters off Cape Cod toward evening.
A northeast to east surface flow will continue in our forecast area
for today. The onshore flow is expected to bring additional clouds
this morning. However, as the center of the high drifts closer, dry
air should begin to nudge into our region with a clearing trend
anticipated from the northeast and east during the afternoon.
The onshore flow should prevent any location in our forecast area
from reaching 90 degrees today. Highs are expected to favor the
lower and middle 80s.
Short term /6 PM this evening through 6 am Sunday/...
the center of the high is forecast to elongate from west to east
tonight as it drifts southward. As a result, the onshore flow in our
region will likely weaken.
Dry air will continue to work its way into our forecast area and we
are anticipating a mainly clear sky.
The lack of cloud cover and the diminishing wind should allow
temperatures to drop into the upper 50s and lower 60s at most
Long term /Sunday through Friday/...
the synoptic setup is comprised of a ridge across the east and a
trough in the west to start. As the trough ejects eastward across
the northern plains and Midwest Sunday into Monday, the portion of
the ridge in the northeast and middle Atlantic is forecast to flatten
some from the north. The initial trough lifts well into Canada late
Wednesday and Thursday with another one then gradually sliding east-
northeast Thursday and Friday. The model guidance has been slowing
the associated surface cold front/S/, which is due to the lagging of
the upper-level feature plus some ridging near the southeastern U.S.
Coast. It still appears that a warming airmass will overspread the
area next week for awhile, and generally dry conditions to continue.
The County Warning Area needs rain, however it looks like the chances are low given no
significant systems moving through although the late week front may
end up stalling in our vicinity and open the door for increased rain
chances. We used a model/continuity blend for Sunday into Tuesday, with
a 00z wpc guidance/continuity blend thereafter. Some adjustments
were then made after additional collaboration with our neighboring
For Sunday...an upper-level ridge is in place although it starts to
flatten on the northern side as short waves slide up into Canada. At
the surface high pressure is forecast to be more centered offshore,
allowing the winds to turn from northeast and east to southeasterly.
While this will allow for some moderation in the temperatures over
land, the coastal areas will be cooler. Some moisture off the
Carolina coast should remain south of the area with our County Warning Area mostly
protected by the upper-level ridge and surface high pressure. Some
radiational cooling induced fog however may be around to start the
day pending limited clouds.
For Monday and Tuesday...a similar setup as the ridge looks to slide
a bit farther east as a trough moves across the northern plains and
into the Great Lakes. Our weather should be generally dominated by
surface high pressure anchored offshore, therefore with a better
established southerly flow we look to heat up some more. It also
looks like the humidity starts to creep back up more toward
For Wednesday through Friday...the initial upper-level trough/closed
low looks to track well into Canada Wednesday, however another one
in its wake moves from the northern plains to the Great Lakes and
may sharpen with time. There may be a surface trough in our vicinity
Wednesday with perhaps a few showers or thunderstorms for the
interior during peak heating, otherwise the main cold front
continues to slow. This is mainly due to the initial energy tracking
so far to our west and north, and therefore the front may arrive
late Wednesday but then either stall or start to washout across our
area. There is less certainty with the upper-level trough to our
west and how amplified it becomes. This will affect how quickly the
front arrives along with any possible weak surface lows that develop
along it. There is the chance of a lead short wave that develops a weak
surface low along the initial/lingering front in our vicinity, then
the main front should approach late Friday. We blended in the new
00z wpc guidance with continuity given less certainty with the
timing and details. This allows for chance probability of precipitation for convection
especially Thursday and Friday.
Aviation /08z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
An onshore flow will likely keep MVFR ceilings over much of our
region for most of this morning. Scattered IFR ceilings are possible
in New Jersey and in the elevated terrain of the Poconos.
Ceilings should lift and the cloud cover is anticipated to become
scattered for this afternoon. A mainly clear sky is expected for
tonight with patchy fog possible, especially away from urban
centers. As a result, we may need to mention visibility restrictions
for late tonight at krdg and kmiv. The two locations are usually
more susceptible to fog than our other six taf sites.
A northeast to east wind around 8 to 12 knots is expected for today.
Wind speeds should drop to 6 knots or less for tonight with the
direction favoring the northeast or becoming variable.
Sunday and Monday...a chance for early morning fog mainly at the
more rural terminals, otherwise VFR. East to southeast winds 4-8
knots Sunday /diminishing at night/, then turning more south and
southwest on Monday.
Tuesday and Wednesday...VFR overall. A few showers or thunderstorms
cannot be ruled out Wednesday afternoon, especially north and west
high pressure located over northern New England early this morning
will sink to the south during today and tonight. A brisk onshore
flow is anticipated for today with wind speeds decreasing tonight.
We will continue the Small Craft Advisory until 600 PM for our ocean
waters north of Atlantic City where the wind gusts should fall below
25 knots by late in the day. We will extend the advisory until
midnight for our waters off Atlantic City and points southward to
allow winds and seas a chance to subside there. The winds should
take a little longer to diminish in the south as the tighter
pressure gradient drifts southward.
The Small Craft Advisory for lower Delaware Bay has been extended
until 200 PM with wind gusts near 25 knots anticipated near the
mouth of the Bay until that time.
No advisory is in effect for upper Delaware Bay which should be
sheltered from the strongest of the wind gusts.
Sunday through Wednesday...high pressure anchored to our east for
much of this time frame will allow a southerly flow regime to become
established. While these winds should increase at times, especially
in the afternoon and evening nearshore with a sea/Bay breeze, they
are expected to remain below Small Craft Advisory criteria. The seas
also are anticipated to remain below 5 feet.
we will go with a high risk for the development of dangerous rip
currents for today.
A brisk east northeast surface flow along with an easterly swell and
wave heights in the 4 to 6 foot range will create hazardous
conditions at the New Jersey shore and at the Delaware beaches.
For Sunday and Monday...a northeast to east wind Sunday will turn
southeasterly by late day and also be 10-15 miles per hour. The waves are
forecast to be on the decrease, and as of now the elevated rip
current risk looks to be decreasing Sunday and Monday. For
Sunday, the risk level will mainly depend on how the elevated seas
today subside however the day may start with a moderate risk.
New Jersey...high rip current risk through this evening for njz014-024>026.
Delaware...high rip current risk through this evening for dez004.
Marine...Small Craft Advisory until midnight EDT tonight for anz452>455.
Small Craft Advisory until 6 PM EDT this evening for anz450-
Small Craft Advisory until 2 PM EDT this afternoon for anz431.