Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 211701
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1201 PM EST Tue Nov 21 2017

.SYNOPSIS...
A cold front approaches from the west today and passes through
early Wednesday followed by high pressure. A warm front moves
north Saturday followed by a cold front Saturday night. High
pressure builds to the west Sunday and Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Forecast on track. Mainly sunny day with patchy cirrus. High
temperatures a few degrees above normal due to SW flow ahead of
approaching northern stream trough. Gusty winds this afternoon
20-30 mph, with the highest gusts along the coast due to
increasing surface pressure gradient.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Rather impressive shortwave over the Gulf of Mexico with
convection firing in the right rear quadrant of 100 kt jet
streak. This convection lifts rapidly across FL to off the
Carolina coast this evening. Jet then strengthens to 120 KT
ahead of the sharpening of the northern stream shortwave.

NWP, including the GEFS, SREF and HREFv2 (replaced SPC`s SSEO)
ensembles all support rain moving into NYC/Long Island and S.
CT before sunrise. Have raise POPs significantly from previous
forecast due the observed dynamics and the consensus of the
latest NWP.

Rain will move east of the region by noon though as colder air
rushes in Wednesday afternoon with gusty NW winds and clearing
skies.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Long range models are in good agreement through Fri, with
noticeable differences starting Sat as a shortwave approaching
from the Northern Rockies interacts with a Canadian vortex near
Hudson Bay. This is leading to timing and amplitude differences
with the 00z EC now developing a cutoff low over New England Sun
night. GFS remains open.

As such, no big changes to the previous forecast through the
end of the week, but have cut back on the extent of PoPs
associated with the warm fropa on Sat as models have trended
slower and drier. Southern stream shortwave and developing sfc
low passes well S and E of the area Sat/Sat night as a cold
front moves through the local area. Not much moisture for the
front to work with have kept the forecast dry Sat night.

Since the upper pattern is a bit uncertain next weekend, this
offshore low will need to be watched. If the full latitude
trough amplifies more, the low would shift to the west and could
result in potential impacts.

A secondary cold front with a reinforcing shot of cold air
could bring a few showers to the area on Sun with gusty winds
developing in its wake. Vigorous shortwave in the GFS which EC
is weaker. SCHC to low CHC PoPs with this feature. Soundings
mostly support rain at this time, although could get some wet
snowflakes Sun morning N and W of NYC.

Daytime temperatures are expected to be below normal through
the period, except on Sat in the warm sector. Overnight lows
also below normal except Fri/Sat nights where they`ll be near
normal.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
High pressure slides further of the Mid-Atlantic Coast today. A cold
front approaches from the west tonight.

VFR through at least midnight. MVFR then develops at CT/Long
Island/City terminals from E to W. Low chance at IFR CT/Long
Island Terminals and very low chance city terminals. Should
stay VFR at KSWF through the TAF period.

SW winds increase to around 10-15G20-25KT by mid-late morning.
Winds diminish late this afternoon/early this evening. With
gusts abating during the evening. Winds become light and
variable outside of KJFK/KLGA overnight.

     ...NY Metro Enhanced Aviation Weather Support...

Detailed information...including hourly TAF wind component fcsts can
be found at: http:/www.weather.gov/zny/n90

KJFK TAF Comments: No unscheduled AMD expected. The afternoon
haze forecast is green, with slant range visibility P6SM
outside of cloud.

KLGA TAF Comments: An occasional gust up to 25 kt possible this
afternoon. The afternoon haze forecast is green, with slant
range visibility P6SM outside of cloud.

KEWR TAF Comments: An occasional gust up to 25 kt possible this
afternoon. The afternoon haze forecast is green, with slant
range visibility P6SM outside of cloud.

KTEB TAF Comments: An occasional gust up to 25 kt possible this
afternoon.

KHPN TAF Comments: An occasional gust up to 25 kt possible this
afternoon.

KISP TAF Comments: No unscheduled AMD expected.

.OUTLOOK FOR 12Z WEDNESDAY THROUGH SATURDAY...

.Wednesday...MVFR possible with showers from the NYC metro
terminals east, with low chance IFR at the eastern terminals in
the morning. Becoming VFR throughout by early afternoon. NW
winds G20-25KT possible late morning/afternoon.
.Wednesday night-Saturday...VFR.
NW-N winds G15-25KT possible Wed night.
W-NW winds G15-20KT possible Thu night mainly east.
SW winds G15-20KT possible on Sat.

&&

.MARINE...
SSW increase this evening as a cold front approaches for the
west. Gales now up for this evening over the far eastern waters.

Upgraded the SCA to Gale Warning for the eastern Bays due to
gusts likely reaching gale force for several hours this evening
as high winds mix down over the bays.

The cold front will be moving east of the forecast waters early
Wednesday as high pressure builds to the west.

SCA winds all waters on Wednesday diminish Wed night. Seas on
the ocean may remain elevated into Fri due to a SE swell. Gusts
will approach SCA levels on Sat but should remain below
criteria. An increasing SW flow could bring seas back up to SCA
levels on the ocean late Fri night into Sat.

&&

.HYDROLOGY...
No hydrologic problems are anticipated the next 7 days.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...Small Craft Advisory until midnight EST tonight for ANZ335-338-
     345.
     Small Craft Advisory until 6 PM EST this evening for ANZ330-
     340-350.
     Gale Warning from 6 PM this evening to midnight EST tonight
     for ANZ330-340-350.
     Small Craft Advisory until 6 AM EST Wednesday for ANZ353-355.

&&

$$
SYNOPSIS...CB/24/Tongue
NEAR TERM...CB/Tongue
SHORT TERM...Tongue
LONG TERM...24
AVIATION...Goodman/Maloit
MARINE...CB/24/Tongue
HYDROLOGY...24/Tongue



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