Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
541 am EDT Wednesday Oct 1 2014
low pressure will redevelop off the New England coast through
Thursday as high pressure over eastern Canada builds in from the
northeast. A strong low pressure system over the central United
States will move northeastward into Ontario by Friday and its
associated strong cold front will move through the region Friday
night into Saturday. High pressure will build in behind the
departing front. Another cold front will cross the region around
Near term /until 6 PM this evening/...
upper low crossing PA/New Jersey today with moist cyclonic flow.
Scattered light showers-sprinkles over the area at 530 am should
eventually tend to dry out late today. Precipitable water continues 1.2 inches
so some areas will receive beneficial rainfall...mainly eastern
and northern New Jersey. 00z/1 NSSL WRF favors eastern New Jersey.
Overcast skies this morning should brighten or thin a bit this afternoon to
reveal a little sunset.
Temperatures/winds/dews are a 50 50 blend of the 100z/1 NAM/GFS MOS. Probability of precipitation
are a 3 way blend of the 00z/1 GFS/NAM MOS and the 21z/30 sref.
Short term /6 PM this evening through 6 am Thursday/...
there may be evening partial clearing before bl relative humidity saturates and
develops lows clouds and possibly patchy fog.
GFS MOS temperatures look far too cold since the low pressure system is far
to the east and the cold air advection is weak. Used the NAM MOS temperatures for lows which
are several degrees warmer than the GFS MOS. Even these were raised
a degree or two.
Dews were NAM MOS.
Winds were a 50 50 blend of the GFS/NAM MOS
Probability of precipitation were blended GFS/NAM MOS and lowered in the SW portion of the forecast
area using the 21z/30 sref.
Long term /Thursday through Tuesday/...
an area of high pressure over the can Maritimes will nose westward over the
area on Thursday and expect a dry day but abundant cloudiness as Ely
flow will persist. This high will remain in place for Thursday night
into Erly Friday with low pressure well off the CST of new eng.
Attention then turns to the central Continental U.S. Where a potent low pressure system will
take shape beginning Thursday night. This low will move north-northeastward and
strengthen as it moves into or toward Ontario on Friday.
The models all agree on the fact that this low develops and moves
into or toward Ontario during this time frame, they differ a bit
on the details, as should be expected. The GFS, NAM/WRF and CMC
have a single low structure and bring the low into Ontario by
03/18z. On the other hand, the European model (ecmwf) has a double low structure at
03/18z and is significantly weaker at this time frame (by about 10
mb) than any other model.
It then is interesting that by 78 and 84 hours the European model (ecmwf) model has the
strongest solution with the low, but it is further S and east with the
low center than the other models.
The cold front associated with this low will begin moving eastward and there could be
some precipitation in western areas by sunset Fri, though confidence is low.
Precipitation chances will increase from west to east Friday night and there are
timing diffs with the models as well. The GFS and NAM/WRF generally keep
the heaviest precipitation west of the I-95 corridor through daybreak Sat while
the European model (ecmwf) and CMC are further east. The GFS then brings the heavier
precipitation through during the morning hours while the European model (ecmwf) is about 6 hours
faster. Then precipitation ends from SW to NE during the day behind the cold front passage
as a wind shift from east to west-northwest brings in drier air. There is sill enough
uncertainty in the models to keep confidence lower than average. The
European model (ecmwf) is often too slow with frontal timing, so its interesting
that it is the faster solution here.
One noticeable trend in the 01/00 guidance is improvement in the
second half of Sat, so have lowered probability of precipitation during this time for this
With that said, high pressure moves in behind cold front passage and Sat night through
Monday look dry.
Another weak cold front will cross the region on Mon, but at this time not enough
confidence to put in poops as the European model (ecmwf) is dry while the GFS has
some low probability of precipitation.
On Tue, there could be some additional precip, which the models
develop differently. The European model (ecmwf) tries to develop some from an area of
low pressure which takes shape from some southern stream energy over the
southeastern states and moves northeastward. The GFS has some northern stream and southern
stream energy and possibly another weak frontal passage. Again, for now will just
carry some low probability of precipitation.
Temperatures will generally average near nrml, except for sun in the cold
advection behind the strong fropa, where temperatures will average much
Aviation /10z Wednesday through Sunday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Through 12z...generally variable MVFR and IFR ceilings. Scattered showers.
Light NE wind.
Today after 12z...MVFR/IFR ceilings linger this morning before becoming
VFR around midday to early afternoon. Scattered showers this morning.
Northeasterly winds are expected, mostly in the 8 to 10 knot range.
Tonight...MVFR or IFR ceilings redevelop later on with possibly patchy
1-3mi fog after 06z/2. Light north wind.
Thursday...MVFR conds possible early otherwise VFR. Possible lingering rain showers early
at miv/Acy, otherwise dry. MDT to high confidence.
Friday..VFR Erly. Possible MVFR west late. Rain chances late west. MDT confidence.
Friday night...MVFR/IFR with increasing rain chances from west to east by
daybreak. Rain could be heavy at times, with approaching cold front. MDT
confidence, though low to MDT on frontal posn.
Sat...MVFR/IFR early in rain, heavy at times...increasing to VFR.
Rain ending from west to east during the mrng/afternoon. Cold front passage late morning Erly
afternoon from west to east and wind shift from southeast to west-northwest. MDT confidence.
two weeks after restoration of a lengthy buoy 44065 outage...data
transmission topped at 4pm this past Tuesday afternoon. Ndbc has
been contacted and they will let US know what the problem is.
In the meantime...marginal Small Craft Advisory conditions are forecast for the nnj
waters today. We dont really know what the seas are doing off the
No expansion of the Small Craft Advisory for the remainder of the waters in our 330
Basically NE flow continues through tonight with maximum gusts around 20
knots. Seas build to near 5 feet northern waters...near 4 feet southern
waters and generally 1-2 feet Delaware Bay.
Thursday...Ely flow will persist and there could be Small Craft Advisory conds once
again, with a better chance over the northern waters. However, Thursday is a
marginal day and the latest guidance indicates we may fall just short.
Thursday night into Friday...Small Craft Advisory will likely be needed at some point during
this period as seas increase ahead of an approaching cold front.
Sat...strong cold front passage. Windshift to northwest or west-northwest. Seas will increase further
and Small Craft Advisory will continue. Best chance for Small Craft Advisory wind during this time frame.
monthly clm's have been run.
Marine...Small Craft Advisory from 11 am this morning to 6 am EDT
Thursday for anz450>452.
near term...drag 539
short term...drag 539