Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
638 PM EDT Sat Mar 15 2014
cold high pressure will push into the region from the northwest for
tonight through the early part of next week. Meanwhile, an area of
low pressure is forecast to develop over the Southern Plains and
move northeastward and off the middle-Atlantic coast on Monday.
Another area of low pressure will move across southern Canada and
bring a cold front through the region on Thursday. High pressure is
expected to follow for Friday.
Near term /until 6 am Sunday morning/...
other than a few scattered sprinkles, mainly across our far
northern zones, a cold frontal passage through the area has been
mainly dry and uneventful. Some scattered to broken clouds will
remain across our far northwest locales this evening, before
decreasing overnight. Elsewhere, a mainly clear evening and
overnight is in store. Gusty west-northwest winds will gradually
subside by late evening, but northwest winds around 10 miles per hour will
continue for much of the region through the overnight. Lows will
drop into the middle/upper 20s across the north/west and low 30s over
the Delaware-Maryland-Virginia and metropolitan Philadelphia.
Short term /6 am Sunday morning through 6 PM Sunday/...
fair weather will continue Sunday. We will remain in the decent
pressure gradient ahead of the high over the Great Lakes. Winds will
turn more nearly Sunday...then become NE late. Wind speeds will
increase during the afternoon as a low pressure system begins to
approach from the SW. High temperatures Sunday will be back below
normal with highs mostly in the 30s north/west and low 40s S/E. It will be
partly/mostly sunny during the morning...then clouds will increase
during the afternoon.
Long term /Sunday night through Saturday/...
the most active portion of the extendd forecast occurs Erly in the period.
Cold high pressure will be anchored to the north as an area of low
pressure develops across the Southern Plains and moves northeastward off the southern middle-
The models still are having some differences with respect to this system. However,
a few things have become clearer. The aforementioned high is a bit
stronger which induced a southward shift in the main precipitation shield. The
southward shift seems to have stopped (at least for now), but even with
that, the model diffs in the strength of the high, the low posn and
the quantitative precipitation forecast will make a world of difference in what occurs.
The NAM/WRF which 24 hours ago was the wettest/snowiest solution has
now turned 180 degrees and is the driest.
Despite a stronger high and most of the models keeping their southern
precipitation shield, the GFS has had a significant northward shift with its
15/12z run. This is likely due to its higher quantitative precipitation forecast and forcing at
700 mb, but is suspicious nonetheless and is being ignored for
The CMC and European model (ecmwf) are a bit wetter than previous runs, but both have a
fairly tight gradient. Exactly where that gradient sets up is the
most important question. It still appears as though the heaviest
snow will be over the Delaware-Maryland-Virginia and portion of extreme southern NJ, with
northern portions of the area getting very little, if anything.
It also appears that the brunt of the snow should be over during the
morning hours and the whole event should be done by Erly afternoon if not
Based on the latest fcst, have issued a ws watch for the Delaware-Maryland-Virginia
and portions of extreme southern New Jersey where confidence is highest.
For the counties bordering the watch, it may end up being an advisory
situation, but again, where the gradient sets up will ultimately
determine that. The headlines may need to be adjusted one way or
the other as additional data becomes available.
In many ways, this event is similar to the March 3 system, but
that one continued to shift swd, where at least for now that
progression has stopped.
Beyond this system, the high will exert itself through the Erly
portion of next week and it looks dry. There is a second low that
is forecast to move off the Atlantic CST on Tuesday/Tuesday night but all of the
guidance (except the nam) keeps the low well off the CST, but it would
be rain if any precipitation occurs.
Another low pressure system will be moving across the northern tier on Wednesday and
will bring a cold front across the region later Wednesday into Erly Thursday. This
front could trigger some precip, but temperatures will be warm enough to
High pressure then builds back in behind the front for the end of
The March temperature roller coaster continues. Sun will see temperatures
below nrml, but Monday looks to be the coldest day of the week, with
many areas not getting above freezing as the aforementioned low
impacts the area. Temperatures will rise about 10 degrees on Tuesday and
return to normal by Wednesday. Temperatures will then be well into the 50s Thursday
Aviation /22z Saturday through Thursday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy and surrounding areas.
Early evening scattered to broken cumulus/SC continues mostly across the far
northern portions of the forecast area. The gusty westerly winds
will continue through the early evening before diminishing. Winds
will remain mostly 5 to 10 knots overnight and become more
northwesterly, while skies become mainly clear.
Sunday...winds will turn northerly during the morning then trend
towards NE by afternoon. Wind speeds will slowly increase to 10 to
15 kts by afternoon. Clouds will slowly increase through the day as
the next storm system approaches from the south. VFR expected through
Sun night...conds lowering into to MVFR and IFR categories as snow
builds into our region from the west and SW. The best chances for
snow and lower conds are for the southern and eastern airports. MDT to high
Monday...IFR and MVFR in the morning improving to VFR in the
afternoon as the area of snow moves off the coast. MDT to high
Monday night through Tuesday night....VFR. High confidence.
Wednesday-Wednesday night...mainly VFR with a chance of rain showers lowering
conditions to MVFR at times, especially in the aftn/eve. Low-MDT
Thursday...VFR. High confidence.
based on latest observations through Delaware Bay, we allowed the
Small Craft Advisory to expire at 22z. While a few isolated wind gusts to 25 knots
are still possible early this evening, the overall trend will be
for gradually subsiding winds, with most gusts in the Bay this
evening around 20 knots or less. Elsewhere, the current Small Craft Advisory
remains for our Atlantic coastal waters.
Otherwise, the decent pressure gradient will continue across the
waters tonight and then slowly relax into Sunday. We will continue
the Small Craft Advisory flags as they are presently...with the coastal waters
going until 11 PM. Winds are presently gusting to or near Small Craft Advisory
conditions along the coastal waters. Winds will decrease tonight
and remain sub-Small Craft Advisory into most of Sunday. Winds will shift to north
tonight and then go NE on Sunday. No precipitation is expected tonight or
Sunday. Seas on the ocean 3-5 feet into the early evening...then 2-4
Sun night and Monday...gale force wind gusts are possible,
especially from late Sunday night into Monday morning. A gale
watch has been issued for the ocean and lower del Bay.
Monday night and Tuesday morning...Small Craft Advisory conds anticipated.
Tuesday afternoon through Thursday...no marine headlines are anticipated,
though we could be close to Small Craft Advisory by Thursday behind cold front.
gusty winds of 25-35 miles per hour will occur into the evening 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
into the evening.
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
New Jersey...Winter Storm Watch from Sunday evening through Monday morning
Delaware...Winter Storm Watch from Sunday evening through Monday morning
Maryland...Winter Storm Watch from Sunday evening through Monday morning
Marine...gale watch from Sunday evening through Monday morning for
Small Craft Advisory until 11 PM EDT this evening for