Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
404 PM EST sun Dec 28 2014
a cold front will pass to the southeast this evening.
High pressure will then slowly build in and dominate through
Friday...while low pressure passes well to the south on Tuesday.
Another low pressure system should approach next weekend.
Near term /until 6 am Monday morning/...
cold front now through most of the area as of 20z except far eastern Long
Island and southeast CT. A passing shortwave could still produce a few
spits of light rain over NYC metropolitan and Long Island this
evening...otherwise skies should clear from the northwest...with colder
low temperatures ranging from the upper 30s in/just outside NYC...to the
Lower/Middle 30s across the rest of NYC metropolitan and the coast...to the
middle/upper 20s inland.
Short term /6 am Monday morning through Monday night/...
high pressure will start to slowly build from the west...with
mostly clear skies and colder temperatures. A weakening secondary cold
front should move through from the north on Monday...so after midday
highs in the Lower/Middle 40s...expect slowly falling temperatures Monday
afternoon and then much colder air for Monday night. Low temperatures at
daybreak Tuesday should be near 30 in Midtown NYC...in the 30s most
elsewhere...and in the upper teens in the colder interior valleys
and Long Island Pine barrens.
Long term /Tuesday through Sunday/...
starting off on Tuesday...more of a consensus now with dry weather
prevailing. Current and previous runs of CMC...ECMWF...and GFS keep
precipitation well south of the region in association with the waves of low
pressure riding along the stalled front. Even majority of GFS
ensemble members keep this precipitation suppressed to the south.
Overall...quasi-zonal 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 weekend.
At the surface...very strong high pressure 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.
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
week but again there is uncertainty with the forecast for day 7
through day 8 time frame.
This 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.
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.
Concerning temperatures...Tuesday through Thursday is when the bulk
of the cold air mass is in place with highs hovering near to
slightly above freezing on average. Near normal temperatures return
by Friday and possibly above normal for the weekend. Again...lower
confidence with temperatures next weekend due to aforementioned
Dry weather in the long term until next weekend with the next
approaching low pressure system.
Aviation /21z Sunday through Friday/...
a cold front moves east of the terminals this evening followed by
high pressure building in from the west tonight.
West winds around 5 to 10 knots will veer to the northwest this evening and
Brief -shra possible across city and Long Island terminals this
evening...but confidence is low to include in taf. Otherwise...VFR
expected through tonight.
Flow remains northwest Monday morning 8 to 10 knots.
Outlook for 18z Monday through Friday...
Thursday...VFR. SW wind gusts to 25 knots possible.
cold front should maintain a moderate northwest flow tonight out east...
with wind gusts close to 25 knots and 5-feet seas on the ocean east of
Moriches Inlet at least into this evening if not all night.
Extended Small Craft Advisory out east through tonight.
Small Craft Advisory conds are again possible late Tuesday night through Wednesday...with a
better chance Wednesday night through Friday...when ocean seas are forecast to
reach 5-7 feet mainly east of Fire Island Inlet. This will be
coinciding with colder air moving in and better mixing over the
relatively warmer waters.
no significant precipitation of 1/2 inch or more expected through
Friday. Widespread precipitation possible for next weekend...but it is too
early to tell if it will be significant.
Marine...Small Craft Advisory until 6 am EST Monday for anz350.