Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kokx 160613 

Area forecast discussion
National Weather Service New York New York
113 am EST Tue Jan 16 2018

high pressure to the north of the area will weaken and shift
eastward through Tuesday ahead of low pressure approaching from
the west and a developing coastal low. The coastal low will
move up the coast into the Canadian Maritimes through Wednesday
night. High pressure will then build to the south through
Friday, moving into the western Atlantic this weekend. Low
pressure will then approach from the west early next week.


Near term /until 6 am this morning/...
forecast is generally on track. Sky forecast is tough overnight
with the western edge of the stratocu deck across Li and CT
eroding while another area of strato cu over New Jersey and eastern PA
is encroaching on NYC. With cooling and a continued onshore flow
in the low levels, expect clouds to fill back in across the
entire area.

Otherwise, weak warm advection just above the surface has led
to the development of a stratocu deck across most of the
forecast area, with enough lift as a jet streak approaches for
some light flurries across portions of Connecticut and Long
Island. Otherwise, generally dry conditions prevail as high
pressure to the north continues a dry northeasterly flow. Low
temperatures are expected to be in the teens to mid 20s,
generally at or slightly below climatological normals.


Short term /6 am this morning through 6 PM Wednesday/...
by morning with the high pressure gradually shifting offshore, a
light return flow will allow warm/moist advection to develop
along the coast, increasing into the afternoon as a coastal low
approaches. Meanwhile farther west, a weak clipper will approach
leading to the development of initially light snow across the
interior, where a Winter Weather Advisory is now in effect.
Precipitation will spread from west to east through the day, and
given warming temperatures along the coast, a rain/snow mix
and/or rain can be expected. Highest confidence of snow is north
and west of the NYC area, while the potential for mixed p-types
reduces confidence for the city into Long Island and coastal
Connecticut. With the latest guidance shifting westward with the
low, potential exists for a warmer solution, and therefore lower
totals for the city into coastal areas. The heaviest
precipitation will develop Tuesday night into Wednesday morning,
as one jet streak aloft departs and another approaches,
allowing the surface low to deepen as it moves up the coast. As
the low departs, a return to northwest flow and cold air
advection will allow temperatures to fall once again, with more
snow possible. Precipitation will then taper off from west to
east by evening.


Long term /Wednesday night through Monday/...
on the heels of an upper trough passing offshore early Thursday,
a progressive southern branch of the polar jet becomes dominant
across the lower 48. Global models are in good overall
agreement with this pattern. This will result in a gradual
warmup as the airmass transitions to Pacific origin. Daytime
highs on Thursday will be near freezing, rising to around 50
by next Monday.

Conditions will be mainly dry as a large area of high pressure
over the lower Mississippi Valley translates slowly east and
passes to the south through the week and offshore this weekend.
A southern branch storm system then approaches late in the
weekend into early next week with a surface low forecast to
track up into the Great Lakes. The trailing cold front moves
through Monday night. This is likely to be a rain event with a
deep layered southerly flow preceding the system.


Aviation /06z Tuesday through Saturday/...
high pressure to the north of the area will weaken and shift
eastward through the day today ahead of low pressure approaching
from the west and a developing coastal low.

NE winds 5 to 10 kt will lighten and become light and variable.
Winds remain light out of the east-northeast-east in the morning, then shift
to the east/southeast in the afternoon before shifting back to the east
towards the end of the taf period.

Patchy stratus is observed across the area, making for a tough
ceiling forecast this morning. In general, would expect stratus to
redevelop and become more widespread toward sunrise, with MVFR
ceilings anticipated through much of the day. There is a chance of
flurries or light snow late in the afternoon, mainly northwest of NYC
Metro, but no visibility restrictions are expected at this time
until 23-02z, except a little later at kgon.

Outlook for 06z Wednesday through Saturday...
late tonight-Wednesday...IFR in light snow or a rain/snow mix near
the coast into Wednesday. VFR possible late.
Wednesday night-Thursday...VFR. North-northwest winds g20kt.
Thursday night-Saturday...VFR.


ocean seas will be at least marginal Small Craft Advisory levels into Tuesday
night in developing onshore flow. Flow returns to a
northwesterly direction and begins to gust late on Wednesday,
continuing into Thursday night. Small craft wind gusts and
marginal seas will be likely on the ocean waters through
Thursday night with a chance of small craft gusts across eastern
Long Island Sound and the eastern Long Island bays. Friday
through the weekend winds and seas will be below Small Craft Advisory levels as
high pressure builds to the south and a weaker pressure gradient
resides across the forecast waters.


no significant hydrologic impacts are expected.


NYC National oceanic and atmospheric administration weather radio station kwo-35 (162.55 mhz) is off the
air for an extended period of time.


Okx watches/warnings/advisories...
New York...Winter Weather Advisory from 10 am this morning to 1 PM EST
Wednesday for nyz067>070.
New Jersey...Winter Weather Advisory from 10 am this morning to 1 PM EST
Wednesday for njz002-004-103-105-107.
Marine...Small Craft Advisory until 6 PM EST this evening for anz350-


near term...Maryland
short term...Maryland
long term...dw

National Weather Service Glossary of Abbreviations