Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
640 am EST Monday Dec 29 2014
high pressure slowly builds in through midweek...then slides south
through Friday. A low pressure system approaches next weekend.
Near term /until 6 PM this evening/...
high clouds were beginning to move east of the area as high
pressure builds and shortwave moves into the western Atlantic.
With the clearing conditions and light wind inland areas of
Connecticut began to radiate well and temperatures fell below
forecast values. Adjusted temperatures...wind...and dew points
through middle morning.
A very broad upper trough encompasses much of Canada and extends
into the United States. Aloft a southwest flow will prevail
through today while at the surface a strong and cold high builds
from western Canada and into the eastern states...with a northwest
flow. Rather strong cold advection continues behind a cold front
that moved through Sunday evening. Leaned toward the colder European model (ecmwf)
guidance for highs and even undercut highs inland a degree or two.
Short term /6 PM this evening through 6 PM Tuesday/...
a northwest flow continues tonight through Tuesday with cold
advection also continuing. While the broad upper trough remains in
place with several shortwaves rotating through. One of the waves
moves out of the Central Plains and to south of the Delaware-Maryland-Virginia
Tuesday. The associated surface low will now pass well south of
the region as the cold high dominates. By tonight temperatures
will fall to below seasonal normals and remain below into the
midweek. With the cold trend remaining again used the colder European model (ecmwf)
Long term /Tuesday night through Sunday/...
overall...quasi-zonal middle to upper level flow through Friday with
a ridging trend for next weekend. The main upper level jet will be
aligned in a similar fashion and moving slightly south of the
region for midweek before trending back north of the area for the
At the surface...very strong high pressure of at least 1050mb
builds into the northwest part of the country and this sinks
southeast through midweek. This will be a source for very cold air
and periodic shortwaves will move across the local region to help
with advecting the colder air mass into the region.
The low level environment will also become very dry as diagnosed
by forecast layer precipitable waters around a tenth of an inch
Tuesday through Thursday. This will be on an increasing trend
towards the weekend but again there is uncertainty with the
forecast for day 7 through day 8 time frame.
This uncertainty is conveyed by nearly a 90 degree phase shift
between consecutive runs of the European model (ecmwf) with regards to upper level
height contour orientation. However...did increase probability of precipitation a little
with agreement on precipitation between dgex...GFS...as well as some GFS
ensemble members. Just a matter of precipitation type. This forecast has
a mix of rain and snow...snow probably at onset due to wet bulb
cooling and then changing over to rain with more southerly flow
for next weekend. However...the confidence is very low for day 7
and day 8 time frame...so subsequent forecasts could vary with
timing...placement...as well as precipitation types.
Near normal temperatures return by Friday and possibly above
normal for the weekend. Again...lower confidence with temperatures
next weekend due to aforementioned uncertainty.
Dry weather in the long term until next weekend with the next
approaching low pressure system.
Aviation /12z Monday through Friday/...
northwest flow prevails through taf period as high pressure builds in
from the west.
Northwest winds around 10 kts...veering north in the evening. For NYC
metropolitan...wind direction will predominately be to the right of 310
magnetic...but will likely vary between 310-360 today.
VFR through taf period...with few 030-035 stratocu this afternoon.
New York metropolitan enhanced aviation weather support...
Detailed information...including hourly taf wind component forecasts can
be found at: http:/www.Erh.NOAA.Gov/zny/n90 (lower case)
Kjfk fcster comments: winds generally right of 310 magnetic today.
Klga fcster comments: winds generally right of 310 magnetic today.
Kewr fcster comments: winds generally right of 310 magnetic today.
The afternoon kewr haze potential forecast is green...which implies
slant range visibility 7sm or greater outside of cloud.
Kteb fcster comments: no unscheduled amendments expected.
Khpn fcster comments: no unscheduled amendments expected.
Kisp fcster comments: no unscheduled amendments expected.
Outlook for 12z Tuesday through Friday...
Thursday...VFR. West-southwest wind gusts to 30 knots possible.
made some minor adjustments to wind across the ocean waters as
speeds were a few knots higher than in the grids. Otherwise the
forecast remains on track.
Marginal winds and seas early this morning should subside through
daybreak as winds aloft weaken.
Sub Small Craft Advisory conds today into Monday night with high pressure nosing into
A low probability of marginal Small Craft Advisory gusts Tuesday/Wednesday on ocean waters
with good mixing in cold air advection and as low pressure/S tracks well south of
Small Craft Advisory conds likely Wednesday night through Friday with good mixing and a tight
west/west-southwest gradient between high pressure to the south and low pressure
to the northwest. Low probability for gale gusts on the ocean waters late
Wednesday night into Thursday night. Seas on ocean waters east of fire inlet
could build to 6 to 9 feet...and even 4 to 6 feet on the central and
eastern Li sound Thursday/Thursday night.
no precipitation is expected through Friday. Widespread precipitation
possible for next weekend...but it is too early to tell if it will
Marine...Small Craft Advisory until 8 am EST this morning for anz350.