Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mount Holly New Jersey
946 PM EST sun Dec 28 2014
a cold front will continue to push further south of our region
tonight. Then a weak area of low pressure moves along the front,
stalled to our south, tomorrow. Cold high pressure will ridge
across the region Tuesday and remain in control of the weather
through Friday. A low pressure system and warm front may advance
toward our area next weekend.
Near term /until 6 am Monday morning/...
the surface cold front will continue to slide to our south and east
overnight while drier surface air moves in from the northwest
overnight. Most shower activity has waned early this evening as an
initial vorticity maximum has pushed across the area. However, as a
second moves into the area overnight, middle-level lift is expected to
redevelop and interact with some middle-level moisture and should
enhance some light precipitation across the southern half of the
area, especially southern New Jersey and southern Delaware-Maryland-Virginia. The rest
of the area should remain mostly dry through the overnight, although
some very light rain is possible across the philly metropolitan area early.
Temperatures tonight should still be well above average with plenty
of cloud cover still in place and a lag in the push of the really
cold air aloft. Used a blend of the met/mavmos as both models looked
reasonable with their thermal initializations.
Short term /6 am Monday through 6 am Monday/...
continued rain threat across our extreme south as the last of the
middle-level waves nears late in the morning/early afternoon. After
this wave we should really start to dry out everywhere as more
established zonal flow with ridging upstream takes over.
North-northwest winds will allow for continued drying and
downsloping flow may help to break the cloud deck leaving US with
partly to mostly sunny skies. Temperatures will be several degrees
colder than the past couple of days but we could end up being at or
slightly above average, especially if we get an enhanced downslope
flow to help warm US.
Long term /Monday through Sunday/...
two main periods of focus in the long term. First, the surface low
riding on the stalled front which likely won't bring much in the
way of an impact to US, but a few outlier ensemble members
continue to depict a snow event for Delaware-Maryland-Virginia and southern New Jersey
Monday night through Tuesday. Second is the system next weekend.
First in the Monday night and Tuesday time frame. Changed little
in the going forecast. Most deterministic models, including the
GFS, ECMWF, and CMC show the front pushing far enough south of our
region (generally from the Florida Panhandle to the coast of the
Carolinas by Monday evening) before the secondary low develops
that our region will see little, if any precipitation. This solution
generally has precipitation in our region, if any, confined to central
Delaware-Maryland-Virginia. Uncertainty comes in with some of the sref members, and
to a lesser extent the NAM, holding on to a snowier solution
for much of our region south of phl. Stayed close to the previous
forecast and the drier solution, for one because this has been
rather consistent the last several model runs. Also, all the
deterministic models, including the NAM, show consistent 6 hour
pressure rises of 3mb or more in the wake of the front through
Monday evening at least, suggesting the front should be able to
push well south of the region before stalling.
Wednesday through Friday still look cool and tranquil. Flow aloft
stays mostly zonal, meaning we will likely not see the brunt of
this cold air mass. Still, portions of the Poconos and northwest New Jersey may
not make it above freezing until Friday.
Friday night through Sunday...still watching a system which by
Friday is modeled to be a 500 mb closed low over the SW U.S.. the
GFS and European model (ecmwf) trended considerably slower with the low from Friday
through the weekend. Not surprising, given that they also depict
the Rosby number decreasing through this time. Otherwise, the GFS
stayed pretty close to what previous runs had with the low lifting
to the Great Lakes region, resulting in precipitation for our region
mainly with in the warm sector (in other words, mostly rain). The
European model (ecmwf) on the other hand, which had been showing a track similar to
the GFS yesterday, now brings the low from southern Kentucky east to southeast
VA, leaving our region in the section for wrap around (potentially
wintry) precipitation. The European model (ecmwf) solution is far different than
the tracks of the last several systems, but not totally out of the
question given the large scale pattern change it is modeling (as
shown by the Rosby wave pattern change). Still, given how
stubbornly the pattern has held this winter, am hesitant to
forecast such a drastic change when it is still 5 to 6 days out.
Aviation /03z Monday through Friday/...
the following discussion is for kphl, kpne, kttn, kabe, krdg, kilg,
kmiv, kacy and surrounding areas.
Tonight...VFR. There could be a temporary MVFR ceiling at miv/Acy if any
showers affect them overnight, so we'll cover these with a tempo
group as necessary. Northwesterly winds around 5-10 knots or less.
Continued shower threat from phl southward will shift farther
southward through tonight.
Monday...VFR. Winds veer towards the north-northeast during the
day. We should be precipitation free tomorrow.
Monday night through Tuesday...VFR conditions expected from kphl
and north. At kacy...kmiv...and kilg there is a risk of MVFR
ceilings at times.
Tuesday night through Friday...mostly VFR conditions expected.
today - Monday...sub-sca conditions expected. Seas will continue
around 2 to 4 feet. West winds veer northwest tonight and increase
to around 10 to 15 knots with a few gusts around 20 knots
overnight. Continued veering towards the north-northeast is
expected by tomorrow.
Monday night and Tuesday...occasional gusts near 25 knots are
possible on the Atlantic coastal waters. Otherwise, conditions are
expected to stay below Small Craft Advisory thresholds.
Wednesday...sub Small Craft Advisory conditions expected.
Thursday and Thursday night...westerly winds with gusts near 25kt
are possible, primarily on the Atlantic coastal waters.
Friday...sub Small Craft Advisory conditions expected.