Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
947 PM EST Wednesday Dec 17 2014
high pressure will pass to the north and east of the area through
the weekend...while weak low pressure over the northern Gulf Coast
emerges along the southeast coast on Sunday. This low will track
slowly north and east Monday into Tuesday...passing south of the
area Tuesday morning. Meanwhile...there is the potential for a
strong storm system to impact the area late Tuesday night into
Wednesday as deepening low pressure tracks up into the Ohio
Near term /until 6 am Thursday morning/...
latest water vapor imagery has 500 hpa trough axis stretching back
from Lake Ontario down into Northwest Ohio. This pivots through the tri-
state overnight. Ahead of this...even though moisture is
limited...should have just enough forcing for a mention of
isolated sprinkles. Could also possibly mix with flurries across
some of the northern zones as moisture could extend just deep
enough for ice crystals to form.
Updated low temperatures with blend of lav/met/mav guidance and
they should be around 5-10 degrees above normal.
Short term /6 am Thursday morning through Friday/...
high pressure continues to build in through the period. A tight
pressure gradient will result in a breezy day for Thursday. Went
with the warmer mav MOS for high temperatures based on mixing to 900mb
and a moderate downslope flow component. Overnight lows Thursday
night is an even blend of NAM and mav MOS.
Dry weather continues for Friday with lighter winds. The warmer
mav MOS once again was used for high temperatures based on temperatures aloft.
Long term /Friday night through Wednesday/...
global models...in particular the 12z GFS and European model (ecmwf)...are in
amazingly good agreement with a strong middle week storm system that
takes a track west of the area. Prior to that time...there are
multiple waves of low pressure moving off the southeast coast...with some
uncertainty in the northern extent of one of these waves Monday night
into Tuesday. The latter of which the European model (ecmwf) is more aggressive with in
taking the low the farthest north...while the ggem and GFS are
suppressed to the south. Preference though is toward a more
amplified pattern in the last 24h...so leaning toward the European model (ecmwf).
This all spells out a prolonged period of wet weather from late
Sat night into the middle week period. Thermal profiles are generally
warm with perhaps a light rain/snow mix Sat night into
sun...primarily north and west of NYC.
At the surface...high pressure passes to the north and east of the
region this weekend. A low-level easterly flow interacts with a middle
level short wave Sat night into Sun morning with possibly light
precipitation. Low pressure then emerges off the southeast coast on sun
and takes a track slowly north through Tuesday. A much more robust
area of low pressure then rapidly deepens across the Tennessee/Ohio valleys
Tuesday night into Wednesday...eventually wrapping up over the Great Lakes
Wednesday night into Thursday with pressures approaching 960 mb. This track
would keep the forecast area in the warm sector of the storm with
the potential for convection and even strong winds. The caveat
here is that the storm is about a week away with a lot of time for
change in track and timing. In addition...the fast Pacific flow would
lead one to believe that there are going to be timing issues with
the southern branch short wave energy.
Temperatures over the weekend start off at nearly normal levels and them
moderate by middle week. Highs near 50 on Wednesday could be underdone if the
pattern and storm track pans out.
Aviation /03z Thursday through Monday/...
deepening low pressure east of New England will move into the
Canadian Maritimes through Thursday.
As the area remains under the influence of the low...sct-
broken 035-050 ceilings should prevail through much of the overnight.
Isolated showers across kgon through 04z. Then isolated rain/snow
showers late tonight for northern and eastern terminals. Potential
for brief MVFR conditions with any snow showers.
Winds generally 290-330 magnetic through Thursday. Winds increase
to near 15-20g25-30kt...highest at the NYC metros...after 05-07z
as a strong disturbance moves across. These winds and gusts should
briefly decrease between 10-12z outside of NYC metropolitan
terminals...then pick up after 14z-15z. Winds and gusts decrease
late Thursday into evening.
Outlook for 00z Friday through Sat...
Thursday night...VFR. Diminishing winds in the evening. Gusts through
the evening for NYC metropolitan terminals.
Sat night...VFR to start...then MVFR or lower conditions with
light precipitation developing. Brief onset as snow possible at coastal
terminals before changing to rain. Slower transition to rain across
interior terminals. Mainly snow at kswf.
Sunday...MVFR or lower conditions...with light precipitation changing to
Monday...chance of rain with MVFR or lower conditions.
minor changes made this update to reflect the latest trends in
observations and guidance. Forecast appears on track.
Winds increase tonight in response to cold air advection and a
tightening pressure gradient. Small Craft Advisory remains posted for all waters
through Thursday...with the ocean waters extended through Thursday
night as gusts to 25 knots continue. There may be a gust or two up to
35 knots over the eastern ocean waters late tonight into early
Thursday morning...but not enough to warrant a Gale Warning. Winds
then subside through Friday with sub-Small Craft Advisory conditions.
Sub-advisory conditions are forecast Sat-Monday as high pressure passes
to the north of the waters. Weak low pressure is forecast to
approach from the south on Monday with a gradually strengthening NE
mainly dry through Saturday. Light quantitative precipitation forecast amounts expected Sat night
into Tuesday. There is the potential for a more significant rainfall
event late Tuesday into Wednesday.
Marine...Small Craft Advisory until 6 PM EST Thursday for anz330-335-
Small Craft Advisory until 6 am EST Friday for anz350-353-355.