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Area forecast discussion 
National Weather Service New York New York
439 PM EST sun Jan 25 2015

Synopsis...
a clipper low over the Ohio Valley late this afternoon will head
east to the central Appalachians by Monday afternoon. A secondary
coastal low will develop and rapidly deepen...becoming a dangerous
winter storm as it tracks slowly north from the middle Atlantic
coast and stalls southeast of Montauk Point late Monday night
into Tuesday...then weakens and moves slowly east Tuesday night.
A weaker system will pass through Thursday night into Friday.
High pressure will follow for Saturday...then a cold front will
move through on Sunday.

&&

Near term /until 6 am Monday morning/...
upper trough slides east of New England tonight with polar high
sliding into New England in wake of a weakening Arctic frontal
passage. With high clouds already streaming in...radiational cooling
will be tempered this evening...with lows generally dropping into
the teens interior and 20s coast. These lows may be too cold
depending on how quickly high clouds stream in. Temperatures should
stabilize overnight with increasing clouds and increasing NE flow.

Thereafter...all eyes on strong shortwave energy diving through the
middle Mississippi River valley this afternoon and into the southeast US
tonight. This will have low pressure tracking along the southeastern
US tonight...and reaching the coast by Monday morning...with
potential for light snow to develop late Sun night into Monday
morning across at least southern and western portions of the
tri-state.

&&

Short term /6 am Monday morning through Tuesday night/...
..a life threatening...Historic winter storm expected from late
Monday into Tuesday...

Nwp guidance continues to bring the ingredients together for a
dangerous...historic blizzard as a secondary low forms off the
middle Atlantic coast on Monday. This low will undergo rapid
intensification as the parent upper low cuts off aloft near the
middle Atlantic Monday night...stalling southeast of Montauk late Monday night
into Tuesday. Mslp drops nearly 30 mb in 24 hour from Monday am to Tuesday
am... before gradually filling.

This will place the forecast area on the northwest flank of the
low. After light warm advection snowfall of 1-3 inches during the
daytime hours Monday in advance of the secondary low...a prolonged
period of MDT-heavy snow expected in the deformation zone.
Followed 12z NAM/European model (ecmwf) closely...with both models supporting quantitative precipitation forecast
upwards of 2 inches liquid equivalent...with the highest amounts
now expected not only across eastern Long Island/CT but also farther
west into SW CT and the NYC metropolitan area/western Long Island...as
models often do not place the area of most intense middle level
frontogenesis far enough west. Snowfall rates of 2-4 inches per
hour expected late Monday night into Tuesday morning. Much of the area
should see amounts of 20-30 inches...locally higher where best
mesoscale snow banding sets up.

In addition...the deep low pressure combined with strong high
pressure to the north and west and heavy falling/blowing snow will
create blizzard conditions across the entire region. A Blizzard
Warning is now in effect...with potential for sustained winds up
to 40 miles per hour on Long Island...and wind gusts ranging from 40 miles per hour
inland...to 50-55 miles per hour most elsewhere...to 65 miles per hour across eastern Long
Island...where a brief hurricane force gust cannot be ruled out.

Temperatures during the storm will generally be in the 20s...except
falling to 15-20 Monday night inland. Wind chills will be mostly in
the single digits to middle teens...but as low as zero to 5 below
across southern CT.

Thanks to all neighboring weather forecast offices...erh and wpc for collaboration
this afternoon.

&&

Long term /Wednesday through Sunday/...
a lingering snow shower could occur over far eastern areas Wednesday
morning...otherwise dry weather...clearing and cold with diminishing
winds. Went below guidance for highs temperatures as well as overnight
lows...considering a deep snow pack in place.

A high pressure ridge is prognosticated to be right over US Thursday
morning. The high shifts offshore...then low pressure approaching
from the west could bring light snow by late in the day to the far
northwest zones. The center of this low is forecast to pass near or through
the County Warning Area at some point Thursday night into Friday. Will continue to
cap probability of precipitation at chance for the entire area during this period...but may
need to eventually bump probability of precipitation up. Precipitation type probably snow for most of
the area...but mixed precipitation would be possible for some coastal areas.

High pressure builds back in on Saturday with below normal
temperatures. A cold front or trough then moves through during
Sunday. Moisture looks limited...but will go with slight chance probability of precipitation
in the grids for snow showers. Temperatures remaining below normal.

&&

Aviation /21z Sunday through Friday/...
** high impact snow and wind event expected late Monday into
Tuesday night...see outlook for details **

High pressure builds down from southeastern Canada through tonight.
Low pressure develops east of the middle Atlantic coast Monday.

VFR conds with lowering ceiling overnight and MVFR conds
increasingly likely through daybreak.

Winds now veering right of 310 magnetic and will continue to veer north
and then NE overnight. Gusts diminish between 21z and 23z...last for
NYC terminals.

NE winds increase Monday morning with gusts of 20-25 knots re-developing.
Increasing potential for IFR conds in snow as the morning progresses.

Outlook for 18z Monday through Friday...
Monday afternoon-Tuesday night...LIFR or lower conditions
developing in blizzard conditions. North winds 20-30kt-g40-50 knots.
Wednesday...VFR. Northwest winds g25-35kt possible.
Wednesday night-Thursday...VFR.
Thursday night into Friday...MVFR or lower conds in snow.

&&

Marine...
Small Craft Advisory gusts across most waters will subside early this evening...but
Small Craft Advisory seas on the ocean with southeast swells will be slow to subside.

Winds and seas increase across all waters on Monday ahead of
approaching low pressure. Gale force easterly wind gusts expected
on the ocean waters during the day on Monday...ramping up Monday night
as winds back northerly to minimal hurricane force on the eastern
ocean waters late Monday night into Tuesday morning...and storm force
elsewhere and also on eastern Long Island Sound and the eastern bays.
The eastern ocean waters may also see sustained storm force winds
during this time.

Wind gusts should subside below gale force on the ocean waters
during Wednesday...with all waters below advisory criteria by late Wednesday
night. Relatively tranquil conditions will follow for Thursday into Thursday
night as a high pressure ridge shifts through. Small Craft Advisory conds are
possible again on Friday...with a low pressure system affecting
the region.

&&

Hydrology...
a major snowstorm expected from Monday into Tuesday night...with liquid
equivalent amounts of 1.5 to 3 inches.

Liquid equivalent precipitation amounts for the system moving through
Thursday night into Friday is currently forecast to be
light...mostly in the form of snow.

Ice on the Wallkill and Yantic rivers is causing minor fluctuations
in river levels at this time.

&&

Tides/coastal flooding...
an intense coastal storm will likely bring moderate coastal impacts
to parts of the coastal region with the late Monday night into early
Tuesday morning high tide. This will bring potential for flooding of
vulnerable shore roads and/or adjacent properties due to height of
storm tide and/or wave action. Several shore Road closures may be
needed.

The uncertainty with the surge is in how quickly winds turn from the
NE to north. An earlier veering of winds to the north ahead of high tide
typically reduces surge in our region.

The most likely surge for coastal areas along western Long Island
Sound is 3 to 4 feet of surge above astronomical tide. A low
probability of 4 to 4 1/2 feet surge above astronomical tide exists.

The most likely surge for coastal areas along eastern Long Island
Sound and eastern Long Island Sound is 2 1/2 to 3 1/2 feet of surge
above astronomical tide. A low probability of 3 1/2 to 4 feet surge
above astronomical tide exists.

The most likely surge for New York/New Jersey coastal areas along New York Harbor
and the South Shore bays of Li/NYC is 2 1/2 to 3 1/2 feet of surge
above astronomical tide. A low probability of 3 to 4 feet surge
above astronomical tide exists.

Significant beach erosion and washovers are expected along ocean
facing barrier beaches of Long Island due to 10 to 15 feet waves and
high storm tide. A few exposed water front structures may be
damaged.

High waves and high storm tide will also cause beach erosion along
north facing shorelines of Long Island Sound and along the Twin
Forks. A few exposed water front structures may be damaged.

&&

Climate...
this blizzard has the potential to produce the largest single-
storm snowfall in NYC history. Here are the current top ten
snowfalls for the city...



Amount dates

26.9 Feb 11-12 2006
25.8 Dec 26-27 1947
21.0 Mar 12-13 1888
20.9 Feb 25-26 2010
20.2 Jan 7-8 1996
20.0 Dec 26-27 2010
19.8 Feb 16-17 2003
19.0 Jan 26-27 2011
18.1 Jan 22-24 1935 and March 7-8 1941
18.0 Dec 26 1872



&&

Okx watches/warnings/advisories...
CT...coastal Flood Watch from late Monday night through Tuesday
morning for ctz011-012.
Blizzard Warning from 1 PM Monday to midnight EST Tuesday
night for ctz005>012.
Coastal Flood Watch from late Monday night through Tuesday
morning for ctz009-010.
New York...coastal Flood Watch from late Monday night through Tuesday
morning for nyz079-081.
Blizzard Warning from 1 PM Monday to midnight EST Tuesday
night for nyz067>075-078>081-176>179.
Coastal Flood Watch late Monday night for nyz074-075-080-178-
179.
Coastal Flood Watch from late Monday night through Tuesday
morning for nyz071-073-078-176-177.
New Jersey...Blizzard Warning from 1 PM Monday to midnight EST Tuesday
night for njz002-004-006-103>108.
Coastal Flood Watch late Monday night for njz006-106-108.
Marine...Small Craft Advisory until 7 PM EST this evening for anz330-
335-338-340-345.
Gale Warning from 6 PM Monday to 6 PM EST Tuesday for anz335-
338-345.
Storm Warning from 6 PM Monday to 6 PM EST Tuesday for anz330-
340-353-355.
Small Craft Advisory until 6 am EST Monday for anz350-353-355.
Gale Warning from 6 am to 6 PM EST Monday for anz350-353-355.
Hurricane force wind warning from 6 PM Monday to noon EST
Tuesday for anz350.

&&

$$
Synopsis...jc/Goodman/NV
near term...Nevada
short term...Goodman
long term...jc
aviation...Nevada
marine...jc/Goodman
hydrology...jc/Goodman
tides/coastal flooding...
climate...tm

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