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Area forecast discussion 
National Weather Service Mount Holly New Jersey
924 PM EDT Wednesday Aug 20 2014

Synopsis...
weak low pressure will move north of the area tonight and Thursday.
Another low pressure system will move south of the area Thursday
night through early Saturday. High pressure will build in from the
north later Friday, then remain for the weekend and into early next
week.

&&

Near term /until 6 am Thursday morning/...
a short wave trough ahead of a closing off upper-level trough
dropping down across the Great Lakes region will lift
east-northeastward through tonight. The airmass across our area is
more stable, however enough moisture combined with some forcing
should result in a few showers through the night. This may occur
especially late as another short wave approaches from the northwest.
Any mainly isolated lingering showers this evening appears to be
tied to weak convergence along the weakening instability gradient.
We will therefore keep some low probability of precipitation in for most places as a few
cells could pop nearly anywhere. The higher probability of precipitation though were
maintained across the northwestern areas especially late, as these
locales are closer to the incoming short wave and some height falls.
The instability looks low enough, therefore did not include thunder
at this time.

Otherwise, enough moisture and the leftover debris clouds should
result in more cloudiness through the night for most locales. The
hourly grids were tweaked based on the latest observations and then
the lamp/lav guidance was blended in to help assist with trends. No
changes were made to the low temperatures at this time.

&&

Short term /6 am Thursday morning through 6 PM Thursday/...
Thursday...another short wave in the west-northwest flow over southern New
York state should redevelop heavy convection during the afternoon over
east PA...possibly extending into west New Jersey and the Maryland East Shore closer to the
convergence of the surface low and inverted trough extending northward from
the vicinity of dca. Precipitable water values are generally forecast around
1.5-1.75 inches, so some showers/storms could produce a period of
moderate to heavy rainfall. Isolated small hail not impossible as
tt near 50 in area of maximum instability in New Jersey (near the Delaware
river).

Forecast basis: probability of precipitation were blended NCEP MOS probability of precipitation with the 09z sref and
that gives the best chance for some needed rain to east PA. Otherwise a 50
50 blend of 12z/20 NCEP MOS except blended rgem sky with NAM sky
and GFS MOS guide.

Near or slightly above normal temperatures.

&&

Long term /Thursday night through Wednesday/...
the long term forecast starts off with rain chances, before a drying
out period sets in across the area.

The weak areas of low pressure to the north (thu night and
friday) and the south (friday through saturday) will force US to keep
low chance probability of precipitation or slight chance probability of precipitation for those periods. The systems do
not look strong enough to produce any heavy rains however. Dry
weather is expected for Sunday into early next week. High pressure
will build in from the north/northeast allowing dry air to
overspread the area.

Temperatures through the long range will start near normal
Friday...before dropping to below normal for the weekend and next
Monday. Readings will rebound back to near normal next Tuesday and
then possibly go above normal Wednesday.

&&

Aviation /02z Thursday through Monday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.

Overnight...VFR overall with ceilings at or above 4000 feet. A few
showers should be around especially north and west of kphl.
Southerly winds 5-8 knots diminishing to under 5 knots. There could
be some localized MVFR ceilings with fog toward daybreak, especially
if the clouds thin for a long enough period of time.

Thursday...generally VFR ceilings. Some showers and thunderstorms
are expected to occur especially farther inland, which may lower
ceilings and visibilities to briefly IFR. The greatest concentration
of showers and storms may be in portions of eastern Pennsylvania
during the afternoon. Southerly winds generally 5-10 knots,
although potentially locally gusty briefly with a thunderstorm.

Outlook...
Thursday night through Saturday...mostly VFR. Showers with lower
conditions are possible.

Sat night through Monday...mostly VFR.

&&

Marine...
no marine related headlines through Thursday.

East-southeast winds between 5-15 knots.

Outlook...
Thursday night through Friday night...sub Small Craft Advisory conditions west/ scattered showers.
Sat through Monday...low end Small Craft Advisory seas expected on the ocean. Mostly fair weather.

&&

Phi watches/warnings/advisories...
PA...none.
New Jersey...none.
Delaware...none.
Maryland...none.
Marine...none.

&&

$$
Synopsis...O'Hara
near term...gorse
short term...drag
long term...O'Hara
aviation...gorse/O'Hara
marine...drag/O'Hara

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