Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
1037 am EDT Friday Mar 27 2015
low pressure will form along a cold front east of the middle
Atlantic coast this afternoon and head northeast out to sea late
Saturday. At the same time. Strong Canadian high pressure is
expected to build into the region through Monday. Another cold
front will cross the region later on Monday. High pressure will
move in again for Tuesday and Wednesday before another low
pressure system affects the area by Thursday.
Near term /until 6 PM this evening/...
as of middle/late morning rain has mostly ended over the area except
for some sprinkles...probably not measurable. There is more rain
to the SW over Virginia/Maryland which will likely clip delmava and southern New Jersey
later today...as suggested by latest rap and hrrr guidance. Skies
are expected to remain cloudy or mostly cloudy for the rest of
today with SW flow at middle/hi levels...although somewhat drier air is
coming in on north-northwest winds at low levels.
The combination of low-level cold advection and cloudy skies will
limit maximum temperatures this afternoon well below yesterday's mild
readings. The maximum temperatures forecast grid was adjusted downward
slightly according to the latest mav/met guidance.
Short term /6 PM this evening through 6 am Saturday/...
a surface trough is forecast to drop through our area from the
northwest this evening. It will usher a reinforcing shot of cold
dry air into our region. The trough is not expected to bring any
precipitation with it. We are forecasting variable cloud cover for
A northwest wind should remain around 10 miles per hour for tonight. Minimum
temperatures are anticipated to be mainly in the 20s in the north
and in the lower and middle 30s elsewhere.
Long term /Saturday through Thursday/...
the period starts out with a large and anomalously cold upper trough over
the eastern Continental U.S. On Sat and a surface low well off the Atlantic coast. Strong
high pressure is located to the west. There remains some disagreement in
the models as to precipitation chances on Sat, but both the GFS and European model (ecmwf) have
trended lower. However, with the strong trough and the
aforementioned surface low possibly creating a surface trough and the strong
northerly to northwesterly flow, there could be some showers/shsn triggered across the
region, so will maintain low probability of precipitation. The best chances would be closest to
By Sat night, the low pulls further away and the 500 mb trough moves
off the CST as the high pressure settles to the S. These features will
allow for a dry and cool day.
The high moves further southeast on Monday which allows for low pressure to
move across southeastern Canada. The attendant cold front from this low will
cross the region later Monday and could touch off a shower, mainly over
northern areas. Will continue low probability of precipitation to account for these
High pressure then builds back in for Tuesday before another weak low dives
southeastward for Tuesday night into Erly Wednesday. This low looks to bring another
round of light precipitation mainly to northern areas.
Finally, by Thursday a more organized area of low pressure will approached
the region and bring more widespread rain chances. Models still differ
on the timing, which can be expected at a week out.
Temperatures will start out as much as 10-15 degrees below normal on Sat,
rise a bit on sun but still remain about 10 degrees below normal
then return to near normal values for the remainder of the period. There
will be a very nice warm up on Monday in advance of the cold front passage. Temperatures
may be knocked down a couple of degrees on Tuesday behind the front
before climbing again during the midweek period.
Aviation /14z Friday through Tuesday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg,
kilg, kmiv, kacy, and surrounding areas.
As of middle/late morning...VFR conds are noted at all our taf sites
except miv/Acy. Some MVFR or IFR conds are likely there for the
rest of today...mainly lower ceilings...as some light rain moves
across from the SW. Some sprinkles or very light rain are possible
along the ilg-phl-ttn corridor but not enough to affect VFR conds.
Winds today will continue light north-northwest...but the chances for
gustiness are looking less favorable than earlier. If gusts do not
develop soon they will be removed from the tafs.
drying will take place today with an improvement solidly into the
VFR category after the rain ends. VFR conditions are forecast to
continue into tonight.
A northwest wind around 10 knots is anticipated for today and
tonight. The wind may gust near 20 knots at times into this
Sat...mainly VFR. Some lower conds in low probability shra/shsn. MDT
Sun - Monday...VFR. North wind veer towards the SW Erly Monday and begin to
gust in the 20 to 25 knots range Monday after. Cold front passage Monday with wind shift to west-northwest
or northwest. MDT to high confidence.
Tuesday...VFR. High confidence.
cold advection will continue on the coastal waters of New Jersey
and Delaware this morning with a reinforcing shot of cold air
arriving tonight. The wind is expected to remain from the
There may be gusts around 25 knots on our ocean waters through
this morning and again late tonight. Meanwhile, wave heights are
forecast to remain in the 5 to 7 foot range today before falling
to around 4 feet for tonight. We will keep the Small Craft
Advisory going for today and tonight, even though conditions may
drop briefly below the criteria for a time this evening.
We have discontinued the Small Craft Advisory for Delaware Bay.
However, we will be issuing a new one that begins at midnight to
account for the wind gusts associated with the next shot of cold
air that arrives tonight.
Sat...Small Craft Advisory will be continued into Sat as strong north to northwesterly flow
will keep both wind and seas elevated.
Sat night - Tuesday...possible Small Craft Advisory conds Sat night and again on Mon,
with some marginal gales even on Sat night into Erly sun. Through
Tuesday. These look to be the most probable times for Small Craft Advisory though
there could be some other more marginal events such as on Tuesday.
Marine...Small Craft Advisory until 6 PM EDT Saturday for anz450>455.
Small Craft Advisory from midnight tonight to 6 PM EDT
Saturday for anz430-431.