Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
652 am EST Sat Feb 6 2016
high pressure will remain over the area today. Low pressure is
forecast to develop off the southeast coast this weekend and track
northeastward late Sunday and Monday. Another low pressure system
may develop in its wake near the middle-Atlantic coast Monday night
into Tuesday. Arctic high pressure is then expected to build in
from the north and west during the latter part of the week.
Near term /until 6 PM this evening/...
a quiet and pleasant February day is expected with an area of
high pressure stretching across the Middle-Atlantic States. Other
than some cirrus spilling into the region, ample sunshine is
anticipated. Light and variable winds in the morning will increase
some and take on a southwesterly direction during the afternoon,
with speeds averaging 5 to 10mph. Daytime high temperatures will
be right around normal for early February, reaching mostly into
the lower 40s, except some upper 30s across northwest New Jersey and the
Short term /6 PM this evening through 6 am Sunday/...
fair weather is expected to continue through tonight across our area
as high pressure gradually moves east and offshore. There may be
some remaining cirrus across the region into the evening, and then
clearing conditions are expected into the overnight. Winds will
again become light and variable, as well. Guidance shows some
warming will be taking place in the low levels overnight, so despite
the light to calm winds and mainly clear conditions, minimum
temperatures overall should be a couple of degrees milder than
Friday night. We blended met/mav guidance with continuity and
anticipate lows to be mostly in the middle to upper 20s.
Long term /Sunday through Friday/...
water vapor satellite imagery captures two separate shortwave
troughs over the central and Southern Plains overnight. These
systems are forecast to phase to some degree as they move into the
Gulf Coast region this weekend. Surface cyclogenesis is forecast to
occur off the southeast coast Saturday night as significant height
falls ahead of the upper low reach the warm waters of the Gulf
Stream. The exact track the low takes and how quickly it deepens
will determine the impacts to our area, if any, late Sunday into
early Monday. Unfortunately, there is still plenty of model
disagreement that has made it challenging to determine what the
outcome will be. One general Camp of models has the low bombing out
and tracking closer to the eastern Seaboard. The other Camp is more
progressive/less amplified with the upper trough, resulting in a
track that is harmlessly out to sea. Regardless of the differences,
just about all of the guidance keeps the low far enough offshore to
spare our area from direct impacts from this storm (e.G., Heavy snow
and strong winds). With that said, this storm still bares watching.
Many of the models for days leading up to the past two storms (the
late January blizzard and the one yesterday) had a distinct
eastward bias in the track. Both of these storms wound up taking
very similar tracks closer to the coast and followed the strong
SST gradient that has been present just to the west of the
anomalously warm Gulf Stream current. Accordingly, we favor these
western solutions and have introduced low chances for rain/snow in Delaware
and New Jersey. Forecast uncertainty still too high to include snowfall
amounts although we cannot rule out the potential for light
Our attention then turns upstream to a digging upper low over the
Great Lakes region on Monday. As this system approaches the eastern
Seaboard, model guidance indicates secondary cyclogenesis occurring
off the middle-Atlantic coast Monday night-Tuesday as the primary low
approaches from the west but they differ with regards to where
exactly the secondary low forms. These Miller-b type setups are
notoriously tricky. If the Miller b low forms to our south and
farther offshore like the 12z European model (ecmwf) and 00z NAM indicated, then
setup would favor lighter snow (starting out as a rain/snow mix or
just rain especially as you get closer to the coast) from the
primary low for our area. If the low develops at our latitude and
deepens quickly closer to the coast like the 00z GFS/ECMWF/Gem had
indicated, then parts of our area could be in line for a band of
heavier snow back to the west along an inverted/norlun trough. Since
our snowfall forecast only GOES out 72 hours from now (thru Monday
night), the amounts on the webpage only include part of the storm.
Did not stray too far from wpc and neighboring offices...a general 1-
2 inches of snow for Monday night. Stay tuned to the latest
forecasts since they will be refined as the uncertainty decreases
After an active start to the long term, a more docile weather
pattern appears to be in store the second half of the week. We could
see a few snow showers with the passage of the main upper trough on
Wednesday. Behind that, a shot of Arctic area takes aim for the middle-
Atlantic and northeast states toward the end of the week. Meanwhile,
surface high pressure building in from the west will keep US dry on
Thursday and Friday. Followed guidance from wpc/super blend closely
in days 4-7. Temperatures along and west of the fall line may not reach
freezing late in the week.
Aviation /12z Saturday through Wednesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Today and tonight...VFR conditions are expected through the taf
period with only some cirrus passing overhead. Light and variable
winds are expected through the morning hours, followed by a
southwest wind developing during the afternoon with speeds mostly
between 6 to 8 knots. Into this evening and tonight, winds will
again become light and variable with a little remaining cirrus or
Sunday...VFR and light winds.
Sunday night...the greatest impacts from strong storm system is
currently expected to remain offshore. However, any westward shift
in the track may bring a period of light rain and/or snow to eastern
Monday and Tuesday...precipitation may overspread the area Monday afternoon
and evening. It may be warm enough to start out as rain near the
coast and a rain/snow mix near I-95. Eventually it will likely turn
over to snow from northwest to southeast Monday night and continue into Tuesday
evening. Potential for IFR restrictions especially once it changes
over to snow. There is moderate uncertainty in the timing of the
changeover and high uncertainty with regards to snowfall amounts.
Wednesday...improving conditions. Mainly VFR although there is a
small risk for a brief restriction with a passing snow shower.
through today and tonight, sub-advisory conditions are expected with
winds out of the northwest this morning becoming more southwesterly
this afternoon and evening. Seas are mainly expected to range
between 2 to 4 feet for the Atlantic coastal waters, with 1 to 2
foot seas into Delaware Bay.
Sunday...no marine hazards are expected.
Sunday night and Monday...a gale watch was issued for the coastal
Atlantic waters for Sunday night and Monday morning. An offshore low
is expected to deepen rapidly to our east during this time. There is
a potential for north-northeasterly winds to reach 35 knots if the low takes a more
westward track. If the low takes a more offshore track, then winds
will be weaker and capped at Small Craft Advisory levels.
Monday night through Wednesday...another area of low pressure will
develop off the middle-Atlantic coast. An extended period of Small Craft Advisory
conditions likely during this time. It could potential reach gale
force late Wednesday but uncertainty is very high regarding the
strength of the winds.
a strong area of low pressure is forecast to track off the East
Coast Sunday night and Monday. A second area of low pressure will
follow closely behind with this one developing as it's moving off
the middle-Atlantic coast Monday night and Tuesday. With persistent
northeasterly flow around these two storm systems expected to
occur across our area at a time when astronomical tides are
elevated from the upcoming new moon, there is a potential for
coastal flooding particularly along the New Jersey and Delaware coasts as well
as the lower Delaware Bay. The latest etss and nyhops ensemble
guidance indicates the potential for minor to perhaps moderate
coastal flooding at times of high tide Monday and Tuesday. The
morning high tide on Tuesday will come with the highest
astronomical tide, so this one could come with the greatest risk
for moderate tidal flooding.
Marine...gale watch from Sunday evening through Monday morning for