Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
620 PM EDT Monday Oct 20 2014
low pressure will forecast to pass off the middle Atlantic coast
on Tuesday night. The low is then expected to move slowly north
and northeastward reaching the waters off Cape Cod around Thursday
night and arriving in Nova Scotia on Friday night. High pressure
is anticipated to build into our region from the southwest for
Friday into Saturday. A cold front approaching from northwest is
expected on Saturday night with another area of high pressure
following for Sunday and Monday.
Near term /until 6 am Tuesday morning/...
the air mass continues to modify tonight with deeper layer
moisture expected to arrive after midnight. The lead impulse,
within the larger Great Lakes trough, nears from the west as its
surface inflection slowly dives into northwestern Pennsylvania
late tonight. We continue with chance probability of precipitation across our western
zones starting early Tuesday morning as the low approaches with
its weakening frontal boundary.
Temperatures will feel balmy compared to this mornings lows.
Expecting overnight lows in the middle to upper-40s in most places. A
blend of the met/mav worked best.
Made some minor adjustments to cloud cover and temperatures with this
update. Latest radar has some weak returns west of the area. But will
see where they are for the next update.
Short term /6 am Tuesday morning through 6 PM Tuesday/...
a filling surface low pressure system to our northwest slides
further south late tomorrow morning and becomes more broad. There
will likely be a dry slot setting up across the central portion of
our cwa, though the exact placement is still suspect. A better
defined and stronger coastal low forms off the Delaware-Maryland-Virginia late in
the day and moves towards the northeast...lots of jet dynamics
involved. Chances for showers increases to likely during the day
mainly across our western and northern zones, though still not
entirely sold on a completely dry day elsewhere so we continue the
chance probability of precipitation. Not looking at a complete washout tomorrow with
widely scattered showers the most probable. We keep thunder out of
the forecast, even with steeper middle-level lapse rates forming, as
the better dynamics offshore could rob inland areas of all the
luster. Temperatures will continue to climb with the modifying
air mass and southerly ahead of the low pressure system.
Long term /Tuesday night through Monday/...
a upper level jet extended from western Hudson Bay, across
western Ontario to the western part of the Great Lakes region this
afternoon. A middle level low is forecast to develop in the lift
under its left front quadrant tonight over the Lake Huron
vicinity. The middle level low is expected to be located over eastern
West Virginia on Tuesday evening and it should pass off the
Delaware-Maryland-Virginia coast on Wednesday morning. The feature is then
anticipated to meander off our coast from Wednesday afternoon into
Thursday evening before lifting northeastward and reaching the
waters off Cape Cod on Friday morning. A surface low is forecast
to follow the middle level low closely during the period.
We are expecting the potential for rain from Tuesday night
through Thursday morning. The possibility of moderate to heavy
rainfall should be mostly on the east side of the developing middle
level low. As a result, we are not anticipating much moderate to
heavy rainfall in our region. The only exception is in our coastal
areas from Tuesday night into Wednesday where rainfall amounts may
approach an inch at some locations. Also, marginal instability in
that area may translate into isolated lightning and thunder.
Regardless, the expected rainfall totals should not result in any
As the low begins to pull away to our northeast on Thursday
night, the potential for rain showers should end gradually in our
A couple of reinforcing middle level short waves should drop over
our region from the northwest in the cyclonic flow around the
departing middle level low over the coming weekend. The short waves
are not expected to have much moisture associated with them.
Therefore, we are not anticipating any precipitation at that time.
A middle level ridge from the west should build toward our region
for Sunday and Monday.
Daytime highs are forecast to be a bit below normal with the rain
on Wednesday and Thursday. Readings should return to near normal
for the period from Friday through Monday.
Aviation /22z Monday through Saturday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Tonight...mostly VFR. Southerly winds around 10 knots become
light and variable late this evening. Some patchy MVFR
drizzle/mist is possible at Abe/ridge early Tuesday morning. High
confidence except for mist development.
Tuesday...mostly VFR. Weak low pressure system nears from the
west-northwest. Winds start off light out of the south, maybe
southeast, and veer towards the southwest late in the period. Keep
low confidence on shower impacts at terminals so keep the mention
out for the time being. Medium confidence.
Tuesday night through Thursday...conditions varying between VFR
and MVFR in periods of rain.
Thursday night...mainly VFR with a chance of showers.
Friday through Saturday...mainly VFR.
tonight...sub-sca conditions expected tonight. Southerly winds
may gust into the low-20 knot range for a time as seas remain
around 3 feet.
Tuesday...sub-sca conditions. Winds back towards the south-
southwest tomorrow afternoon and begin to decrease as weak low
pressure moves in overhead. Seas remain 2 to 3 feet.
Tuesday night...no marine headlines are anticipated.
Wednesday...northerly wind gusts of 25 to 30 knots are possible.
Wednesday night through Friday night...northwesterly wind gusts
of 25 to 30 knots are possible.
Saturday...no marine headlines are anticipated.