NYC Office Forecast Discussion

000
FXUS61 KOKX 181043
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
543 AM EST Sun Nov 18 2018

.SYNOPSIS...
High pressure over New England will shift offshore today, with
a weak warm front approaching tonight. A slow moving cold front
will sag south of the region on Monday, followed by the passage
of a weak offshore low on Tuesday. An arctic airmass will
likely build in for the end of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast is on track. Minor updates to hourly T/Td and winds
based on latest obs and trends. Otherwise, despite high
pressure over New England, skies will remain gray as jet induced
cloud cover and pcpn move towards the area from the Ohio
Valley. The high shifts offshore this aftn with the possibility
of some light pcpn well N and W of NYC late this aftn as the
entrance region of an upper jet streak with weak shortwave
energy tracks into New England. Soundings indicate this would
fall as snow, with only a coating expected through 6pm.

Highs are expected to range from mid to upper 30s well inland to
mid 40s near the coast.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
Guidance remains in good agreement with an amplifying pattern
developing across the lower 48 early this week as a piece of
the polar vortex breaks off and drops into Hudson Bay. This will
result in a developing longwave trough east of the Rockies with
a high amplitude ridge to the west.

At the sfc, a weak frontal system will track from the mid
Mississippi valley into the Mid Atlantic states by evening and
continue through southern New England tonight. WAA will ensue
tonight ahead of a warm front with temps slowly rising in the
low levels. Pcpn is expected to gradually expand southward,
although NYC and Long Island may remain mostly dry until
Mon night and Tue. With the warming low level temperatures any
snow across locations well inland this evening is expected to
change over to plain rain overnight. Less than an inch of snow
accum is expected before the changeover.

Weak low pres continues towards the Canadian Maritimes on Monday
with its cold front slowly pushing south of the area. PoPs
decrease Mon aftn/eve as weak ridging moves through ahead of the
next wave of low pres. There is some uncertainty in the track of
this low which will depend on where the energy in the base of
the upper trough tracks and the interaction between this and
additional southern stream energy ejecting from the SE coast.
This will also determine where the axis of heaviest pcpn will
be. Pcpn overspreads the area late Mon night with all NWP
guidance tracking the low S of Long Island on Tue. Colder temps
across northern zones should gradually change the pcpn back over
to snow into Tue morning. Boundary layer temps are progged to
become marginally warm as the pcpn is lifting out which may lead
to a changeover back to the liquid state before ending. At any
rate, boundary layer temps will be marginal across the interior
where accumulating snow is expected late Mon night into Tue,
which will result in a wet snow. As such only anticipate 1-2
inches of accumulation. If the axis of heaviest pcpn shifts a
bit further N or the wetter GFS verifies, could be flirting
with advsy level snow. Areas from the CT coast and south are
expected to remain all rain through the duration of the event.

Temperatures are expected to range between 5 and 10 degrees
below normal through Tue.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Fair wx Wed with the cwa between systems. An arctic front
however arrives Wed ngt. The GFS and ECMWF both agree on this
timing. Although the models are dry, some snow shwrs cannot be
ruled out. Pops may need to be included in later forecasts.

Dry wx fcst for Thanksgiving thru Sat with a 1040 or so high
building in. Temps well blw average on Thanksgiving, then moderating
a bit each day thereafter. Rain possible Sat ngt as a Pacific sys
approaches.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
High pressure will slowly build from the NW this morning.
The high moves offshore this afternoon with a warm front approaching
tonight.

VFR through this afternoon. There is potential for ceilings 2500-
3000 feet late this afternoon into tonight. Light precipitation
moves into the terminals this evening north of NYC. KSWF may start
off as some light snow, but will transition to rain towards
midnight. Just some light rain is expected for the remainder of the
terminals.

W-WNW winds diminish through the early morning hours, veering to NW-
N and then N-NE after day break. Winds continue to veer to the SE
this afternoon. Speeds will be under 10 kt.

.OUTLOOK FOR 06Z MONDAY THROUGH THURSDAY...
.Sunday night...MVFR or lower conds possible in chance wintry mix
inland with chance rain elsewhere.
.Monday...MVFR or lower conds possible with chance of rain.
.Monday Night-Tuesday...MVFR or lower conds possible in rain or
wintry mix Monday night into Tuesday morning, then chance of rain
Tuesday afternoon. NW winds G15-20kt in the afternoon.
.Tuesday Night-Wednesday...VFR. W winds G15-20kt.
.Wednesday Night-Thursday...VFR. NW winds 15G25kt.

&&

.MARINE...
High pressure passing over the waters today will keep conditions
below SCA criteria through tonight.

Winds and seas are forecast to remain below SCA levels through
Wednesday. An arctic front move across the waters Wednesday night
bringing SCA and low chance of gale conditions Wednesday night into
Thursday. Winds and seas then fall below SCA levels on Friday.

&&

.HYDROLOGY...
QPF amounts between 1/4" and 1/2" are expected from late this
afternoon into Tuesday. Some of this is expected to fall in
solid form across interior locations. No hydrologic issues are
expected through next Saturday.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off
the air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.

&&

$$

NWS OKX Office Area Forecast Discussion