Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
854 PM EDT Tuesday may 5 2015
a cold front will slowly move through our region overnight and
Wednesday. High pressure will then move into the area from the
north and east on Thursday through the weekend. Another slow
moving cold front will approach our area early next week...and
move through the region by middle week.
Near term /until 6 am Wednesday morning/...
we are anticipating an increase in cloud cover overall for the
nighttime period. Additional middle level clouds along with some
stratocumulus should overspread our region from the west.
The showers and isolated thunderstorms that extended from eastern
Maryland southwestward to central Virginia around 845 PM will
continue to push to the southeast. Meanwhile, the area of showers
over western New York and parts of northern Pennsylvania are
forecast to slide to the east southeast. They should affect our
northern counties overnight. The scattered showers that were over
central Pennsylvania are expected to dissipate for the most part
as they move eastward.
Based on the radar trends, we will continue to mention only
isolated to scattered rain showers for the overnight period.
Rainfall amounts are anticipated to be modest, generally a trace
to a tenth of an inch.
The surface front was rather diffuse and difficult to find this
evening. It appeared to extend westward from southern New England
into northern Pennsylvania around 845 PM. The boundary is expected
to move southward through most of our forecast area by morning.
The wind is forecast to remain light for tonight. It will favor
the west and northwest this evening and it should veer toward the
north and northeast late tonight. Low temperatures are expected to
range from around 50 in the north to near 60 in the south.
Short term /6 am Wednesday morning through 6 PM Wednesday/...
the front is expected to be south of our forecast area on
Wednesday morning. There are a couple of more vorticity impulses
that are forecast to slide across the area Wednesday. There will
remain decent moisture around behind the front, with precipitable water values
near 1.0-1.25 inches, so we will keep isolated/scattered showers
in the forecast through the day Wednesday.
Long term /Wednesday night through Tuesday/...
middle-level ridge slowly moves over the northeast Continental U.S. Thursday through
Sat...with weak shortwave disturbances traversing it. Meanwhile...a
cut-off low develops in vicinity of the southeast US coast...and this may
acquire subtropical characteristics during this time frame.
Overall...there will be a general blocking pattern along the East
Coast which may become Rex-like attms. This will lead to a ridge
of high pressure at the surface through the weekend...and gradually
give way to a cool front approaching from the northwest by early next
week. Generally fair weather expected through the weekend... with an
increasing chance of rain showers/thunderstorms and rain with the approach of cool front sun
through early next week. Maximum temperatures will be near average
through the period...cooler near the coast Thursday through Sat with
onshore flow. By Sunday...the air mass may turn increasingly
Wednesday night...a weak shortwave will move through the region with
favorable jet dynamics. This will lead to some overrunning along a
slow moving frontal boundary just to our south. Weak lift and
limited moisture may support some -shra over the southwest County Warning Area.
Thursday and Friday...both days will feature a weak shortwave moving
through the region during the afternoon time frame. This induces a
weak surface trough...with a sea-breeze along the coast...which will
enhance surface convergence. There will be more moisture available on
Thursday...so -shra are possible...mainly northwest of the I-95
corridor. Stability indices do not support thunder at this time.
Also...there may be some patchy fog Friday am...mainly over the
northwest interior...per synoptic pattern and model soundings.
Saturday and Sunday...Ridge builds surface and aloft on Sat...
and gradually moves southeast on Sunday. Surface flow gradually veers
from the southeast on Saturday to southwest on Sunday. A cool
front will approach the Saint Lawrence valley by 00z Sunday...with
the GFS much more progressive than the Euro thereafter with the
southward progression of the front. Given the blocking pattern
along the East Coast...and the ridge anchored over the middle-
Atlantic...favor the slower solution. Feel general subsidence will
keep the column dry/capped across the County Warning Area...but cannot rule out
-shra/thunderstorms and rain making it into the northwest portion of the County Warning Area on Sun afternoon.
Monday and Tuesday...as the cool front approaches...there will be
greater moisture, lift, and instability available. Given a slow
frontal passage with ample Gulf/subtropical moisture, and
favorable jet dynamics...heavy rainfall is possible during this
Aviation /01z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
We will continue to forecast VFR conditions through the taf
period. Scattered to isolated light rain showers should have
limited impact on our taf sites.
A light and variable wind overnight should settle into the
northeast on Wednesday morning around 5 to 10 knots. The wind
direction is anticipated to veer toward the east for Wednesday
Wednesday night and Thursday...generally VFR...except MVFR possible in
-shra... mainly confined to phl, pne, ilg, Abe, ridge.
Friday through Sat night...VFR conditions expected.
Sun...VFR conditions may deteriorate to MVFR over the interior in
sub-Small Craft Advisory conditions are expected tonight into
Wednesday. Seas will remain 3-4 feet, and south-southwest winds.
However, as the front passes through, winds will diminish and
Thursday through Sat...persistent onshore out of the southeast. Winds are
expected to remain below Small Craft Advisory criteria. However...there is a low
probability that seas may approach Small Craft Advisory levels by Saturday.
Sun...sub-sca conditions expected.