Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
402 am EST Sat Nov 29 2014
high pressure over the area this morning will pass east this
afternoon. A warm front will approach this afternoon and move
slowly across tonight into Sunday night...followed by a cold front
on Monday. High pressure will return on Tuesday...before another
frontal system moves across Tuesday night into Wednesday night.
Another high will briefly build in on Thursday...then yet another
low pressure system will approach at the end of next week.
Near term /until 6 PM this evening/...
first approaching area of middle level clouds heralding warm air advection has
dissipated...but more middle level clouds with better upper support
via a middle level shortwave will be on their way after sunrise...
with skies becoming mostly cloudy west of NYC late this morning
and elsewhere this afternoon. This shortwave in tandem with lower
level isentropic lift is producing an area of light snow from
western PA to the WV Panhandle...but as the shortwave outraces the
isentropic lift...think any light snow will have trouble holding
together...so expect no more than a flurry or two northwest of NYC
Despite warm air advection...clouds should hold high temperatures at levels not much
different than those of yesterday...with lower 40s in/near NYC
and middle/upper 30s elsewhere...close to warmer NAM MOS guidance.
Short term /6 PM this evening through Monday/...
increasing warm air and moisture advection with the approaching
warm front should maintain mostly cloudy skies tonight. Low temperatures
are likely to be reached this evening...with Lower/Middle 30s for
NYC metropolitan and coastal sections and 25-30 elsewhere...once again
per warmer NAM MOS...then expect steady temperatures inland and slowly
rising temperatures elsewhere. Upper level moisture will pass to the NE
later tonight into Sunday morning but low level moisture at levels
too warm for ice nucleation will continue to increase...with
enough lift via overrunning late tonight plus passage of a
shortwave Sunday morning to produce some patchy drizzle or
freezing drizzle...mainly in Orange County. Will have to monitor
this for potential issuance of a Freezing Rain Advisory late tonight
into Sunday morning.
Temperatures should warm up nicely during the day on Sunday...with upper
40s well north/west of NYC and Lower/Middle 50s elsewhere...then lows
ranging from the middle 30s to middle 40s Sunday night.
A cold front passing through on Monday will be moisture starved...
with only slight chance of a shower. Expect one more mild day with
highs once again from the upper 40s to middle 50s...then colder weather in
its wake for the long term.
Long term /Monday night through Friday/...
cold front will be well to the south by Monday evening...with cold air advection on
gusty northwest winds in its wake. With Arctic high pressure building
from the north in its wake...expect dry conds Monday night...but an
upper jet streak and middle level shortwave moving across should
maintain Post-frontal cloudiness until Tuesday morning. Temperatures should
fall several degrees below normal by Tuesday morning.
Moderating polar high builds in Tuesday...with dry but unseasonably
cold conditions. Temperatures will likely run 10 degrees below
normal...with high generally in the 30s.
Uncertainty in the forecast increases for the middle to late week as
models differ in the interaction of shortwave energy rotating around
a closed polar low northwest of Hudson Bay and its interaction with
northern stream energy. The 28/12z CMC/European model (ecmwf) and associated
ensembles were aggressive with this interaction...pivoting a
phased and strong shortwave through the northeast Wednesday night.
The 28/12z GFS was tame with this interactions and signaling a
practically flat upper flow...while the 28/12z gefs depicted a
more amplified shortwave passage. Have leaned toward the more
amplified flow as depicted by the ensemble means. In terms of
sensible weather...a return flow Tuesday night in wake of exiting
polar high and approaching shortwave and associated frontal
system...should spell an increasing chance for precipitation Tuesday night
into Wednesday. Thermal profiles support wintry precipitation to start Tuesday
night...then gradually changing to rain from S to north on Wednesday. Cold
air damming could make freezing rain stubborn across interior tri-state on
Wednesday. This system should exit Wednesday night as the shortwave axis
pivots through...with another glancing shot of cold air advection in its wake.
Moderated polar high pressure will likely build in on Thursday...with
dry and below seasonable temperatures. Then models were in good agreement
with a Pacific shortwave and associated quick moving low pressure
approaching late week...but timing into region differs from Thursday
into Friday based on above mentioned differences with the prior
northern stream shortwave. Having favored more amplified and
slower pattern...have delayed chance probability of precipitation with the next shortwave
Aviation /08z Saturday through Wednesday/...
high pressure will continue to build in overnight and pass east of
the terminals by late morning.
VFR. Winds were generally light and variable with a weak northwest
flow around 5 knots at the NYC terminals. During Saturday the wind will
become southerly and remain under 10 knots...as the high shifts east.
Middle level warm advection clouds move in prior to daybreak and remain
through Sat. Brief period of MVFR ceilings with patchy drizzle after
00z...mainly at kswf.
Outlook for 06z sun through Wednesday...
late Sat night-sun...patchy drizzle and MVFR conds across the lower
Hudson Valley...otherwise VFR.
Sun night-Mon...MVFR conds possible. Some patchy drizzle late
Sunday night at kswf...otherwise chance of rain showers.
Wednesday...chance of rain with MVFR or lower conds.
high pressure moves off the coast today and tonight as low pressure
moves through the Great Lakes region. A southerly flow will increase
through the day and into tonight as a warm front approaches and
moves north Sunday. Sustained wind should remain below small
craft...however...gusts to small craft will become likely tonight
and continue into Sunday. Will be a marginal event...as warmer air
will be advecting over cooler ocean waters limiting the mixing. Best
chances for small craft will be the ocean and eastern sound and
Peconic and gardiners bays. Will issue a small craft for tonight and
Sunday for these waters.
Gusts are expected to diminish below 25 knots Sunday evening and remain
below until the passage of a cold front late Monday. Then small
craft gusts across all the forecast waters will be possible Monday
Seas on the ocean waters will build to small craft by late tonight
in the persistent and increasing south flow. With a south flow until
Monday with the passage of a cold front...seas on the ocean will
remain at small craft levels into Monday night.
Sub Small Craft Advisory conds then expected by Tuesday as high pressure builds over the
waters...with next chance of marginal Small Craft Advisory conds possible on the
ocean waters late Tuesday night into Wednesday with next frontal system.
no significant precipitation is expected.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST Sunday