Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
601 am EDT Tuesday Sep 23 2014
a high will slide east over the region today and tonight. Tomorrow,
a low is expected to develop off the Carolina coast before lifting
northeast into Delaware-Maryland-Virginia resulting in increased rain chances through
Thursday night. A high centered over the Great Lakes region will
build by Friday bringing a return of tranquil weather.
Near term /until 6 PM this evening/...
high pressure will slide across the area today which will keep the
weather quiet. There is little in the way of low or middle level
moisture forecast today, so we do not expect much thick cloud cover
today. We only expect high level cirrus across the area as the upper
jet will keep a stream of upper level moisture across the area.
Highs today are a blend of mixed 925mb European model (ecmwf) temps, mav/met MOS, and
mosguide which keeps everyone slightly below or right around normal.
Short term /6 PM this evening through 6 am Wednesday/...
high pressure will slide into New England overnight, but still nose
down into the middle-Atlantic and keep fair weather across our area.
The only clouds we expect will be the continuing high level cirrus
overhead which will not have much of an effect on the weather.
Overnight lows are a blend of mav/met MOS and mosguide which keeps
everyone pretty close to normal.
Long term /Wednesday through Monday/...
most of the attention through these periods is focused on Wednesday
and Thursday. Models trended a bit further north with the track of
the surface low. However, there remain some significant differences
between the models on the intensity of the low. The GFS by far is
showing the most and fastest cyclogenesis, which would mean more
impacts especially on our southern coastal and marine zones.
However, with the upper level trough filling and lifting through
this period, would not expect the pattern to support such rapid
cyclogenesis. Thus forecast favors the European model (ecmwf) solution, showing
instead an open inverted surface trough. However, even with this
solution, the further north track could mean more widespread
precipitation, thus have increased probability of precipitation across the region, although
Delaware and southern New Jersey are still the favored areas for rain.
Friday through Sunday...at the surface, a high will build in over
the Great Lakes region. At the same time in the upper levels, a
very high amplitude ridge will develop and slide east. Thus expect
a return to tranquil weather. However, with the center of the
surface high remaining north of the region, we should keep low
level easterly flow, which may slightly temper the warming trend.
Monday into Tuesday...still considerable uncertainty with the
track and timing of a strong cold front. Given the Stout high that
will already be in place, it is uncertain if the front will be
able to propagate this far south. Thus...have kept close to the
previous forecast for now.
Aviation /10z Tuesday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
VFR conditions will prevail through the period as high pressure
builds across the area. We only expect high level cirrus through
today and tonight.
Winds will be mostly northwest to north to start out, then become
more northeast to east later today into tonight as high pressure
slides across the area today, then into New England tonight.
Overall, wind speeds will be fairly light, generally 5-8 knots or
Wednesday and Thursday...MVFR ceilings are possible over much of
the region as a low passes just east of the region. The terminals
expected to have the longest and most significant impacts are kmiv
and kacy which may see IFR ceilings at times. Kabe and krdg will
likely only see MVFR ceilings for a portion of this period, with
breaks of VFR conditions. Occasional MVFR visibilities with -ra
are also possible.
Friday and Saturday...mostly VFR conditions expected.
winds have dropped below advisory for all areas, so the Small
Craft Advisory has been cancelled. Sub- advisory conditions will
remain for the remainder of today into tonight as high pressure
moves across the area and into New England. The pressure gradient
will begin to tighten between the high to our north and a
developing area of low pressure to our south overnight tonight
into early Wednesday morning. Conditions will begin to approach
advisory levels once again by the pre-dawn hours Wednesday.
Wednesday and Thursday...Small Craft Advisory conditions (both winds and seas) are
expected. An Small Craft Advisory for these periods has now been issued. In
addition, on the southern ocean waters, could see a few gusts near
or at gale conditions, but confidence is too low to issue a gale
watch at this time.
Friday...seas slowly decreasing below 5 feet through the day.
Saturday...conditions are expected to remain below Small Craft Advisory criteria.
increasing on shore flow associated with a low moving north along
the coast, combined with higher astronomical tides associated with
the new moon will mean water levels will approach minor coastal
flooding criteria with the high tide cycle on Wednesday night.
However, at this time, guidance shows levels staying just below
minor flooding, so will only mention in the severe weather potential statement for now.
an enhanced rip current risk is likely Wednesday into Thursday
with gusty winds and increasing wave heights.
Marine...Small Craft Advisory from 6 am Wednesday to 6 am EDT Thursday