Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
430 am EDT Sat Mar 15 2014
low pressure located over southwestern Quebec early this morning
is forecast to move down the Saint Lawrence River valley today.
The low is expected to pull a couple of cold fronts through our
region, one this morning and one late in the day. Cold high
pressure will push into our region from the northwest for tonight,
Sunday and the early part of the new week. Meanwhile, another area
of low pressure is forecast to pass off the middle Atlantic coast
on Monday. A frontal boundary is anticipated to approach from the
west on Wednesday and it should pass through our region on
Thursday. High pressure is expected to follow for Friday.
Near term /until 6 PM this evening/...
a couple of frontal boundaries will cross through the area today
as an area of low pressure continues to swing through southern
Quebec. This first is moving through central Pennsylvania this
morning and has a line of showers associated with it. Most of the
model guidance has the precipitation mostly dissipating as it
approaches our area as the strongest forcing associated with the
short wave/vorticity maximum lifts north of our area. Nevertheless, there
still could be some light showers affect a good portion of the
area early this morning. A few sprinkles and light showers have
also developed well ahead of the front across New Jersey and the
Delmarva, but they will be moving off the coast in the next hour
The front is expected to clear the area and be off the coast by 9
or 10 am this morning. Any precipitation will come to an end
behind the boundary and it will also have a wind shift associated
with it, with winds shifting from southwest to west. Winds will
become gusty later this morning into this afternoon, once again
gusting up 25 to 35 miles per hour.
The second boundary is expected later this afternoon. This front
will have another wind shift with it, shifting from the west to
northwest. However, with this frontal passage, drier and cooler
air will be moving in. Dewpoints are expected to drop and
temperatures will be dropping as well behind this boundary.
A blend of mav/met MOS and MOS guide was taken for daytime highs,
which yields temperatures a few degrees above normal.
Short term /6 PM this evening through 6 am Sunday/...
a cooler, drier night is expected tonight across the area as high
pressure at the surface begins to nose in from the west and zonal
flow aloft develops. Any stronger wind gusts from the daytime are
expected to diminish by sunset, but there should remain a steady
breeze much of the night for most places.
A blend of mav/met MOS and MOS guide was taken for overnight
lows, which yields temperatures a few degrees below normal.
Long term /Sunday through Friday/...
cold high pressure is forecast to continue building into our
region from the northwest on Sunday. High temperatures are
expected to be mainly in the lower and middle 40s on the coastal
plain and in the 30s to the northwest of the fall line. Reading
should not get above the middle and upper 20s in the elevated
terrain up north. High clouds are anticipated to overspread our
region on Sunday out ahead of an approaching weather system. Some
middle level clouds may reach the southern half of our forecast area
late in the day with some light rain possibly arriving on the
upper Delaware-Maryland-Virginia at that time.
A northern stream short wave was located over southwestern
Montana and vicinity early this morning with a southern stream
short wave over the southwestern New Mexico area. Some of the
energy from the northern stream system is forecast to drop over
the south central states for Sunday but it does not appear as
though it will fully phase with the southern stream system.
Nevertheless, a fairly robust short wave should result and it is
anticipated to move along the Gulf Coast and vicinity during the
early part of the new week. Meanwhile, the remaining energy from
the northern stream short wave is forecast to scoot eastward and
it should pass over our region around midday on Monday. A
relatively weak surface low is expected to develop ahead of this
feature on Sunday night and it should move out to sea off the
middle Atlantic coast on Monday.
We continue to anticipate some snow in our region from Sunday
night into Monday. While there may briefly be a mix of rain and
snow across our southern counties, conditions should be cold
enough for a mostly snow through the event.
While there is always a danger in comparing an upcoming event to
a recent one, there seem to be some striking similarities to our
March 3rd snowfall. The guidance continues to indicate a very
sharp gradient along the northern edge of the system and it is
expected to run through the Philadelphia metropolitan area. Also,
similar to the event nearly two weeks ago the lift should be
mainly due to the cold air undercutting the somewhat milder air to
its south rather than the bulk of the lift coming from the mild
air over-riding the cold air at the surface. The former scenario
should limit the amount of additional moisture being drawn into
and over our region. As a result, we have lowered the forecast
We are expecting less than an inch of snow across the Poconos,
the Lehigh Valley and northern New Jersey. Our forecast calls for
1 to 3 inches of snow for much of southeastern Pennsylvania into
central and parts of southern New Jersey. The greatest snowfall
amounts in our region will likely be across the south. Based on
our current thinking, we may see 3 to 5 inches on the Delaware-Maryland-Virginia and
into extreme southern New Jersey which would be on the border of
an advisory and a warning. If the forecast snowfall amounts with
this system trend in any direction, our thinking is that it would
be downward based on the model trends and recent experience. As a
result, we will not issue any winter storm watches at this time.
The latest guidance has the snow ending on Monday morning with
perhaps some lingering light snow showers in the afternoon. Also,
the guidance is suggesting that a second wave might bring a little
light snow to our far southern counties from late Monday night
into Tuesday morning, generally less than an inch if it occurs.
The cold high pressure should pull away to our east during the
middle week period. A middle level trough is expected to approach from
the west along with its associated surface cold front. The front
is anticipated to pass through our region on Thursday. There is a
chance of showers on Wednesday and Thursday. Conditions should be
warm enough for mainly rain. Temperatures are forecast to return
to near normal for the second half of the new week.
Aviation /09z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
VFR conditions are expected to persist across the taf sites
through the period. The lowest ceilings are expected this morning
while a frontal boundary crosses the area, along with scattered
showers. However, ceilings are expected to be around 4,000-5,000 feet.
Behind the front, clouds are expected to lift and scatter out
through the day.
Winds will become gusty once again today, with gusts 25-30 knots
expected. Winds will start out of the S-SW, then become SW-west
behind the first front, then west-northwest behind a secondary front later
Any wind gusts are expected to diminish around sunset, but a
steady breeze should remain for much of the night.
Sunday night...conditions lowering into the MVFR and IFR
categories as snow builds into our region from the west and
Monday...IFR and MVFR in the morning improving to VFR in the
afternoon as the area of snow moves off the coast.
Monday night through Tuesday night....mainly VFR.
Wednesday...mainly VFR with a chance of rain showers lowering
conditions to MVFR at times, especially in the afternoon.
two frontal boundaries will cross the waters today into this
evening. Both will bring wind shifts, first from SW-west by later
this morning, then west-northwest by this evening. Winds remain gusty across
the waters, so a Small Craft Advisory remains on the ocean, but
has been extended through 11 PM. A Small Craft Advisory has been
issued for the Delaware Bay as winds are starting to gust around
25 knots already this morning and should continue through the day.
The Delaware Bay advisory ends at 6 PM when winds are expected to
diminish below advisory levels.
Sunday...no marine headlines are anticipated.
Sunday night and Monday...gale force wind gusts are possible,
especially from late Sunday night into Monday morning.
Monday night and Tuesday morning...Small Craft Advisory
conditions are expected.
Tuesday afternoon through Wednesday...no marine headlines are
gusty winds of 25-35 miles per hour will occur once again today across the
area. However, relative humidity values are not expected to be as
low as Friday, but may still get close to 30 percent across the
same areas where we have had an Special Weather Statement the last couple of days.
Therefore we will continue with the Special Weather Statement for enhance fire danger
the developing northeasterly flow will result in an increase in
tidal departures. The full moon occurs on Sunday. However, the
astronomical tides associated with this full moon are rather low
and tidal departures of greater than a foot and a half would be
needed for minor tidal flooding to occur. Being that the low is
not forecast to be particularly strong, the latest extra-tropical
surge guidance is not indicating minor tidal flooding. However, we
will continue to keep an eye on the model trends.
begorah, more snowfall records to fall and/or climbing higher in
the snowfall record department:
Daily snowfall records for:
Allentown 12.0 in 1896 4.2 in 1967
Atlantic City 1.7 in 1978 1.6 in 1965
Philadelphia 4.1 in 1978 3.5 in 1892
Wilmington 2.9 in 1978 2.4 in 1965
In Philadelphia, we have had 13 separate calendar days in which
an inch or more of snow has fallen this season. We have a chance
to make it 15 calendar days which would give this season sole
possession of second place. 14 calendar days occurred in 1898-99
while the record is 17 calendar days in the 1917-18 season.
Speaking of second place, an additional 2.7 inches would give
Philadelphia (62.9 inches currently) the second snowiest season on
record, surpassing the 65.5 inches during the 1995-6 season. The
all-time record is 78.7 inches in 2009-10. It appears safe through
this event. If 6.6 inches or more of snow were to fall early next
week, it would be the first time ever there have been four double
digit months of snowfall in one season in Philadelphia.
Atlantic City (33.7 inches currently) needs one tenth of an inch
of additional snow to crack the top 10 snowiest seasons on record
and 8.7 additional inches to supplant 2002-3 as the 5th snowiest.
The most recent snowiest winter was 2010-11 (ranked 8th) at 38.0
inches. Numero Uno is the winter of 2009-10 at 58.1 inches.
Wilmington (52.9 inches currently) needs 3.1 additional inches to
supplant 1995-6 as the second snowiest season on record. The
record is 72.8 inches during the 2009-10 season.
Allentown seasonal snowfall ranks:
75.4 inches in 1993-4
71.4 inches in 1995-6
67.2 inches in 1966-7
66.9 inches in 2013-4
Marine...Small Craft Advisory until 11 PM EDT this evening for
Small Craft Advisory until 6 PM EDT this evening for anz430-