Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New York New York
1229 am EST Wednesday Nov 26 2014

weak high pressure briefly builds across the area tonight...while
low pressure develops along the southeast coast. The low will
deepen and track northeast on Wednesday...passing just east of
the southern New England coast in the evening. The low then tracks
through the Canadian maritime Thursday. High pressure then builds
in behind the departing low Friday and Saturday. Low pressure
moves well to the north and west Sunday and Monday...bringing a
warm front through Sunday...followed by a cold front Monday. High
pressure builds in Tuesday.


Near term /until 6 am this morning/...
clouds increase throughout the night as low pressure develops and
strengthens off the southeast U.S. Coast. Surface dew points are slowly
creeping up...but it still remains quite dry locally...and there
is little...if any...rain along the eastern Seaboard. Nearest rain
is over the Carolinas. will take some time for
measurable rainfall to reach NYC and Long will push
off chance probability of precipitation until just prior to daybreak.

Temperatures across the interior have dropped into the lower 30s...but
temperatures there should rebound by a few degrees or so as clouds
spread north. Otherwise...lows will drop into the middle to upper


Short term /6 am this morning through 6 PM Thursday/...
significant winter storm will track northeast just off the
eastern Seaboard on Wednesday. There is good model agreement on
taking the low just inside the benchmark Wednesday night...40n...70w.
The real difficult part of the forecast is resolving Thermo
profiles with no real source of low-level cold air. Event will be
heavily dependent on dynamical cooling and where banding sets up.
In addition...any deviation right or left of the low track could
alter Thermo profiles by just a degree or two...all that will be
needed for a significant change to the forecast. Highest
confidence of reaching warning level snows is across the interior
of southern CT...the lower Hudson Valley...and portions of NE New Jersey.
New York metropolitan and much of coastal CT have been placed into an advisory
due to a longer transition time to snow and frequent mixing with
rain. This will be a heavy wet snow...potentially causing power
outages and downed tree limbs.

As previously mentioned...models have come into consensus with a
low track just inside the benchmark Wednesday evening. There is no polar air
in place for low-level cold air with the models varying with an
elevated warm layer in the middle levels. The 18z NAM WRF is the most
aggressive with this warming with 3 degree c at 700 mb across the NYC
metropolitan. Ironically...the NAM about 24 hours ago was the coldest
solution with a track a bit farther east. It still remains the
coldest in the boundary layer...which for the most part is the
hang up for the NYC metropolitan...coastal CT...and western Li...which
are generally below freezing above 1500 feet. The boundary layer
will be critical here. As for the elevated warm layer from the
latest NAM...will have to see if this shows up in the 00z
cycle...particularly the GFS and European model (ecmwf). The NAM is clearly more
robust with an 85 to 90 knots jet at 650 mb. The European model (ecmwf) is about 10 to
15 knots weaker and farther offshore...and the GFS is even farther
east. This could be huge play maker. In addition...with a
marginally cold air mass in place...850-500 mb frontogenesis could
overwhelm the column with significant snows even into the NYC
metropolitan. For now will keep advisory level snows at the coast and
warning level across inland areas. Eastern Li and southeast CT will
see the least amount of snowfall unless a significant track
change ensues in subsequent cycles...which is not likely.

Precipitation will break out by daybreak and be heaviest during the morning
and afternoon hours.

Highest snowfall totals will range from 6 to 10 inches in the
lower Hudson 2 to 5 inches in the advisory area.

Stayed away from MOS temperatures in this situation and used the NAM 2
meter temperatures for boundary layer and a blend of the GFS/European model (ecmwf) for
Thermo profiles and ptype. Temperatures will slowly fall into the lower
and middle 30s by middle after Wednesday.

Expect a transition to all snow on the backside Wednesday night with
minor additional accumulations possible. Lows will range from the
middle 20s to lower 30s.


Long term /Thursday night through Tuesday/...
an upper trough will still be crossing the northeast Thursday into
Thursday evening with the surface low departing to the northeast.
There will be some weak instability along with weak lift with the
upper trough and a weak surface trough in the vicinity behind the
low. Both the GFS and European model (ecmwf) have light quantitative precipitation forecast...and some flurries will
be possible into Thursday evening.

The upper trough axis moves off the coast Thursday night with the
flow becoming zonal into early next week. Some weak ridging builds
Tuesday as a deepening trough moves into the Pacific northwest and
Rocky Mountain range. A very weak shortwave move quickly through the
zonal flow...north of the area...Saturday night into Sunday. A the
surface a warm front crosses the region Sunday followed by a cold
front late Sunday night into Monday morning. There will be a slight
chance of rain showers Sunday into Monday.

For temperatures Thursday through Friday undercut guidance by a few
degrees inland with the potential of snow cover and light northwest
flow. Otherwise followed wpc guidance Friday night through


Aviation /06z Wednesday through Sunday/...
***high impact winter weather event wednesday***

Low pressure will track from near Hatteras Wednesday near
Cape Cod Wednesday night.

VFR most of tonight...falling to MVFR as precipitation starts around
IFR or lower thereafter until after 00z when precipitation tapers off and ceilings
improve to MVFR.

For the city into khpn and kbdr...precipitation starts mainly as rain then
transitions to snow by around 15z. Sleet and rain may then mix in
during the afternoon before ending as all snow in the evening. A period of
all rain is possible somewhere between 19-23z...mainly kjfk and

For kswf...all snow.

For kisp and kgon...transition to snow later than the city...with
more potential sleet and rain mix in the afternoon. Potential for periods
of heavy rain in the afternoon.

Most likely runway accumulations 3-6 inches NYC metropolitan
terminals...8-11 inches kswf...4 to 8 khpn...3-6 inches kbdr...1-2
inches kisp/kgon.

Outlook for 06z Thursday through Sat...

Wednesday night...improvement to VFR. Diminishing northwest winds.

Thursday-Thursday night...lingering snow showers possible in the morning
with MVFR conds...then VFR.



a coastal low brings gale conditions to the coastal ocean waters
Wednesday afternoon and Wednesday night. The Gale Warning remains
unchanged. For the remaining waters...a Small Craft Advisory will be in effect for
roughly the same period.

A northwest flow behind departing low pressure Thursday will be
below small craft levels...however seas on the ocean will still be
at small craft levels and slowly subsiding...falling below by
Friday morning as high pressure builds in.

Then wind and seas will remain below small craft the remainder of
Friday into Saturday. A return flow develops Saturday as the high
moves off the coast. A southwest flow increases as low pressure
moves through the Great Lakes region Saturday into Sunday. Some
gusts on the ocean waters may be near small craft later Saturday
into Sunday...and seas will be building to small craft late Saturday
and remain into Sunday.


for Wednesday and Wednesday night...expecting a liquid equivalent
precipitation amounts averaging around 1.0 to 1.5. The highest quantitative precipitation forecast
amounts area currently expected over eastern CT/Long Island and
the lowest over far western portions of the tri-state.

Over the interior most of this will fall in the form of
little if any immediate hydrologic impact is expected there. Farther
to the S/E...basically along and east of I-95...there will be a a mix
of rain and snow. This could cause minor flooding of urban/poor
drainage areas.

Thursday through Sunday...very light quantitative precipitation forecast amounts are
possible...Thursday...Saturday and Sunday.


Okx watches/warnings/advisories...
CT...Winter Storm Warning from 7 am this morning to 1 am EST
Thursday for ctz005>007.
Winter Weather Advisory from 7 am this morning to 1 am EST
Thursday for ctz008>011.
New York...Winter Storm Warning from 7 am this morning to 1 am EST
Thursday for nyz067>070.
Winter Weather Advisory from 7 am this morning to 1 am EST
Thursday for nyz071>075-176>178.
New Jersey...Winter Storm Warning from 7 am this morning to 1 am EST
Thursday for njz002-004-103-105-107.
Winter Weather Advisory from 7 am this morning to 1 am EST
Thursday for njz006-104-106-108.
Marine...Small Craft Advisory from 10 am this morning to 1 am EST
Thursday for anz330-335-338-340-345.
Small Craft Advisory until 11 am EST this morning for anz350-
Gale Warning from 11 am this morning to midnight EST tonight
for anz350-353-355.


near term...mps/dw
short term...dw
long term...met

National Weather Service Glossary of Abbreviations