Scientific Forecaster Discussion
Area forecast discussion
National Weather Service New York New York
707 PM EST Friday Nov 28 2014
high pressure will build in from the west overnight...and pass to
the east by Saturday afternoon. A warm front will then approach
Saturday afternoon...move slowly across Saturday night into Sunday
night...followed by a cold frontal passage on Monday. High
pressure will follow for Tuesday...before another frontal system
affects the region Tuesday night into Wednesday night. High
pressure will return on Thursday...then yet another low pressure
system may affect the region for the end of the week.
Near term /until 6 am Saturday morning/...
strato-cumulus streamer with scattered flurries...originating from the lakes
and getting enhanced over the Litchfield Hills...drifting southeast
across southern CT toward The Forks of Long Island early this
even...should dissipate through 8-9 PM with waning mixing.
Then temperatures should drop under building high pressure with mostly
clear skies and diminishing winds...at least for the first half of
the night. Middle level clouds moving in late tonight should limit
radiational cooling somewhat from NYC west...so sided with warmer
met guidance there for lows...and with a mav/met blend elsewhere.
Coldest temperatures should be across interior southern CT with 10-15.
NYC metropolitan and most of Long Island should see lower 20s...with
other spots 15-20.
Short term /6 am Saturday morning through Saturday night/...
increasing warm air and moisture advection with the approaching
warm front should bring mostly cloudy skies...also a chance for
afternoon flurries and/or sprinkles especially northwest of NYC.
High temperatures should be similar to those of today...mainly 35-40.
As the warm front slowly lifts to the NE Sat night at least
aloft...chances for flurries/sprinkles will shift over to southern
CT and eastern Long Island. Low level moisture should however
continue to increase...especially north/west of NYC...where weak
transient shortwaves may be enough to help produce some patchy
light drizzle or freezing drizzle north/west of NYC.
Long term /Sunday through Friday/...
models in decent agreement with the upper flow regime across the
Continental U.S. Through Monday...with zonal upper flow being interrupted by a
couple of pieces of northern stream energy digging into the northern
plains sun and then swinging through southern Ontario/Quebec through
Monday night. A resultant low pressure system will take a track just
to the north of that...with its associated warm front moving north
sun and then its cold front approaching Sun night and then crossing
Monday. Forcing is weak on Sunday...but soundings indicate low/middle
level warm air advection and saturation...which should result in considerable
cloudiness and some patchy drizzle and isolated shower activity sun
through Sun night...particularly across interior portions of
Surface cold front passes through Monday afternoon with cold air advection on gusty
northwest winds in its wake. With shortwave energy making its closest
approach late Monday into Monday night and region under right rear quadrant
lift of strong upper jet...a low chance for a period of light
Post-frontal precipitation exists before middle-level moisture axis pushes
offshore later Monday night. CMC ensemble...gefs...and the 00z/12z
European model (ecmwf) support this. Any precipitation should be rain Monday after...but then
changing to snow from northwest to southeast before ending Monday night. Little to
accumulate expected at this time. Arctic air mass remain shunted well to
the north...but temperatures should fall several degrees below normal by
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 CMC/European model (ecmwf) and associated ensembles are
aggressive with this interaction...pivoting a phased and strong
shortwave through the northeast Wednesday night. The GFS is tame with this
interactions and signaling a practically flat upper flow...while
the gefs depicts a more amplified shortwave passage like CMC/European model (ecmwf)
ensembles. Have leaned towards 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
Moderated polar high pressure likely builds in on Thursday with dry
and below seasonable temperatures.
Model 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 until Friday.
Aviation /00z Saturday through Wednesday/...
high pressure will continue to build in through tonight.
VFR. Northwest winds right around 310 magnetic early this evening before
winds become light and variable late as ridge axis moves overhead.
Middle level warm advection clouds move in after 06z and remain
through Sat. Possible MVFR ceilings after 00z for 30h tafs.
Outlook for 00z sun through Wednesday...
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.
northwest winds to gust to 25 knots through the evening on the outer ocean
waters...so Small Craft Advisory has been extended until 1 am. Winds on the eastern
sound have fallen just below 25 knots and will continue to subside
through the evening...so the advisory will be allowed to expire
at 7pm. Quiet conds later tonight into Sat as high pressure builds
Increasing SW flow should result in another period of Small Craft Advisory conds on the
ocean and possibly the eastern sound/bays Sat night.
Small Craft Advisory ocean seas are likely on Sunday...with marginal SW Small Craft Advisory winds
continuing. South-southwest Small Craft Advisory swells could linger on the ocean...
particularly east...into Monday afternoon. Small Craft Advisory seas could continue
into Monday night with a period of marginal northwest Small Craft Advisory gusts possible
in wake of a Monday afternoon cold frontal passage.
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 until 1 am EST Saturday for anz350-353-
Small Craft Advisory until 7 PM EST this evening for anz330-