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Area forecast discussion 
National Weather Service New York New York
501 am EST sun Jan 25 2015

Synopsis...
a clipper low over the middle Mississippi Valley this morning will
track to the Middle Atlantic States by Monday morning...where a
secondary coastal low will develop. This storm will rapidly deepen
and become a powerful Nor'easter as it tracks slowly north toward
the New England coast by Tuesday evening...and then up into the
Canadian Maritimes by late Wednesday. A weaker system will pass
through Thursday night into Friday.

&&

Near term /until 6 PM this evening/...
the upper air pattern features a broad upper trough from the Lee
of The Rockies to the East Coast...which will undergo major
amplification as a digging short wave trough over the MS valley
carves out a full latitude East Coast trough by Monday.

In the meantime...a short wave passing through eastern Canada
today will send a cold front through the area this afternoon.
Polar high pressure behind the front over the Great Lakes builds
east into the northeast tonight...laying down the foundation for
cold air ahead of the next storm system.

West winds will veer around to the northwest this after behind the cold
front with gusts up to 20 miles per hour. Some high clouds will begin to
filter in late in the day.

Highs will be 35 to 40...warmest near the coast. Stayed close to
met/mav MOS.

&&

Short term /6 PM this evening through Tuesday night/...
high pressure noses in from the northwest tonight with clouds gradually
lowering and thickening ahead of a clipper low moving across the
Ohio Valley. Warm advection ahead of the system may allow for
light snow and/or flurries to work into the area prior to daybreak
Monday.

The ingredients are then coming together for a possible historic
Nor'easter as a secondary low forms off the middle Atlantic early Monday.
This low undergoes rapid intensification as the low cuts off aloft
near the middle Atlantic Monday night...lifting slowly northward through
Tuesday night. Mslp drops nearly 30 mb in 24h from Monday to Tuesday
morning...before gradually filling. This will place the forecast
area on the northwest flank of the low with a prolonged period of MDT-heavy
snow in the deformation zone. Most of the global models and their
ensemble members members supports upwards of 2 inches liquid
equivalent...with the highest amounts across eastern Li/southeast CT.
That being the case...snow banding will likely extend as far west
as the lower Hudson Valley with snowfall rates of 2 to 4 inches an
hour at times. Much of the area should see a foot with amounts as
high as 2 feet possible across eastern Li/southeast CT. Once again
though...the exact location of the most intense banding is
difficult to pinpoint at this juncture.

The 00z NAM continues to be an outlier on the eastern flank of
the low track and its significantly lower precipitation has been
discounted.

In addition...the deep low pressure combined with strong high
pressure to the north and west will create near or blizzard
conditions across much of the region. A blizzard watch has been
posted for Li and much of the southern CT...with a Winter Storm
Watch elsewhere. Potential exists for gust of 35 to 50
miles per hour...highest to the east.

Light snow develops Monday morning and then gradually picks up in the
late after. MDT-heavy snow will fall for much of Monday night into Tuesday
before tapering off Tuesday evening.

Temperatures during the storm will generally be in the 20s with wind
chills in the single digits to middle teens.



&&

Long term /Wednesday through Saturday/...
behind the storm...dry weather Wednesday and Thursday...then a
weaker low affects US Thursday night into Friday. Capped probability of precipitation a
chance for snow...with precipitation more likely to be snow...but
mixed precipitation not out of the question.

&&

Aviation /09z Sunday through Thursday/...
** high impact snow and wind event probable late Monday into
Tuesday night...see outlook for details **

A cold front crosses the area today. High pressure builds down from
southeastern Canada this evening.

VFR through the taf period...except brief period of MVFR at kswf
through 11z. Ceilings fall to around 5000 feet towards the end of the
taf period.

Winds are mainly west-northwest around 10-15kt. West-northwest-northwest winds g15-20kt by late
this morning. Gusts will abate by late afternoon. Winds veer to the
north at city terminals by middle-late evening at around 10 knots...and become
light and variable elsewhere.

Outlook for 06z Monday through Thursday...
Monday morning...MVFR possible in -sn. East-east-northeast winds g20-25kt
probable.
Monday afternoon-Tuesday night...IFR/LIFR conditions likely in
snow. Blizzard conditions possible west/probable east with potential for
heavy snow and NE-north winds g35-50 knots.
Wednesday...VFR. Northwest winds g25-35kt possible.
Wednesday night-Thursday...VFR.

&&

Marine...
Small Craft Advisory conditions will persist across most waters through sun after.
Winds and seas will fall below Small Craft Advisory this evening.

Winds and seas increase Monday morning into Monday afternoon ahead
of a strong storm that will develop along the middle Atlantic coast.
The storm will pass to the east of the waters Tuesday...and then
northeast Tuesday night into Wednesday.

Have issued a gale watch for New York Harbor...South Shore bays....and
western Long Island Sound and a storm watch for all ocean
waters...eastern Long Island Sound...and Peconic and Gardners bays.
Strongest winds and highest seas will occur Monday night into
Tuesday afternoon as the storm passes. Used wavewatch as a starting
point for waves...but increased by several feet in coordination with
surrounding offices. Potential exists for a few gusts over Easter
ocean waters and eastern sound to approach 60 knots.

Winds and seas then diminish Wednesday and Thursday as the storm moves NE
and high pressure approaches from the west.

&&



&&

Hydrology...
potential for a major snowstorm Monday into Tuesday with liquid
equivalent amounts of 1 to 2 inches. Precipitation type however
does appear to be mostly all snow...reducing adverse hydrologic
impacts during the storm. There is still uncertainty with these
amounts.

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

&&

Tides/coastal flooding...
a potential intense coastal storm could bring minor to locally
moderate coastal impacts to the region Monday night into Tuesday
morning.

&&

Okx watches/warnings/advisories...
CT...blizzard watch from Monday afternoon through Tuesday evening
for ctz006>008-010>012.
Winter Storm Watch from Monday afternoon through Tuesday
evening for ctz005-009.
New York...blizzard watch from Monday afternoon through Tuesday evening
for nyz078>081-177-179.
Winter Storm Watch from Monday afternoon through Tuesday
evening for nyz067>075-176-178.
New Jersey...Winter Storm Watch from Monday afternoon through Tuesday
evening for njz002-004-006-103>108.
Marine...gale watch from Monday afternoon through Tuesday afternoon for
anz335-338-345.
Small Craft Advisory until 5 PM EST this afternoon for anz330-
335-338-340-345-350-353-355.
Storm watch from Monday afternoon through Tuesday afternoon
for anz330-340-350-353-355.

&&

$$

Synopsis...dw
near term...dw
short term...dw
long term...jc/dw
aviation...ds
marine...ds
hydrology...jc/dw
tides/coastal flooding...NV/dw

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