Area Forecast Discussion
Issued by NWS Upton, NY

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FXUS61 KOKX 220315
AFDOKX

Area Forecast Discussion
National Weather Service New York NY
1015 PM EST Tue Nov 21 2017

.SYNOPSIS...
A cold front passes through early Wednesday as intensifying low
pressure tracks well southeast of the region. High pressure
builds in Wednesday through the end of the week. A cold front
crosses Saturday night, with high pressure building in from the
west for the beginning of next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Baroclinic leaf evident of cyclogenesis seen nicely on
satellite this evening along the SE US coast as southern stream
energy lifts up the coast. The phasing of approaching northern
stream energy from the Great Lakes with this southern stream
energy, should result in a favorably strong right entrance jet
region over the region late tonight into Wednesday morning. This
lift interacting with Gulf/Atlantic moisture advecting up the
coast should allow for a soaking rain across eastern portions of
the region tonight. In fact, high res models indicating
potential for some weak instability promoting a period of heavy
rain and perhaps an embedded rumble of thunder. The exact
location of deformation zone will determine how far west the
heavier rain develops, with high-res models clustering across
LI/CT. With large scale lift, a period of light to moderate rain
likely for NYC/NJ metro, with just some lighter rain potential
to the NW.

Rain develops late tonight from southwest to northeast, mainly
between 06-09Z.

Total rainfall amounts generally between a half to 1 inch for
Eastern Long Island and eastern Connecticut, with low prob of 1
1/2 inches. To the west, rainfall will taper to about about a
1/10 to 1/4 of an inch for the NYC/NJ metro, with lower totals
NW of NYC/NJ metro.

Lows generally in the 30s across NW interior, with 40s
elsewhere.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Once the cold front passes during the morning, conditions are
likely to quickly improve from west to east during the early
afternoon with drier air ushering into the region. With cold air
advection following the front, the end result will be falling
temperatures throughout the day along with an increase in breezy
NW winds by afternoon.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Continued agreement with the operational models for the first part
of the long term period. High pressure at the surface, with the
center over the Mid-Atlantic states, will keep the area dry for
Thanksgiving. Cold air advection continues as noted in 12Z GFS
soundings, so conditions will be much cooler than Wednesday. Given
forecast soundings and 850 temperatures in the 0 to -4 C range for
much of the area, highs should only reach the lower 40s, which is
below normal for this time of year. Normal highs should be in the
lower 50s. A cold front does pass north of the area, with a wind
shift to the west, then west-southwest by the afternoon.

High pressure pushes off the East Coast late Friday into Friday
night as a warm front over the Eastern Great Lakes lifts well north
of the area. Warm air advection doesn`t seem to kick in until Friday
evening, so dry and continued cool for Friday, but slightly warmer
than Thursday with highs in the middle to upper 40s.

Another cold front approaches the area late Saturday and passes
through Saturday night. Southwesterly flow ahead of the front will
bring temperatures to normal levels to above normal levels, in the
upper 40s to upper 50s. 12z GFS has trended drier with this run,
which will warrant only slight chance for the entire area as there
isn`t much moisture for the front to work with. It may be cold
enough at the start for some frozen or freezing precipitation in
much of Orange County Saturday morning, however, it will quickly
change to rain.

A surface trough or secondary weak cold front moves through on
Sunday with a reinforcing shot of cold air. Some instability with
the colder air aloft associated with the upper level trough may
produce some light rain showers across the area, mainly for portions
of Long Island.

High pressure then keeps the area dry through the beginning of next
week.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
A cold front will approach tonight as low pressure moves up the
coast. The front will pass through during Wed morning.

VFR most of the night, then rain will spread into the terminals late
tonight into Wed morning with MVFR conds developing, except then IFR
conds at KISP/KGON. Rain likely ends by around noon for the city
terminals and points west, and early afternoon farther east.

S-SW winds diminish tonight then shift NW and increase Weds morning,
prevailing north of 310 magnetic. Gusts then become frequent during
the aftn 20-25 kt.

.OUTLOOK FOR 00Z THURSDAY THROUGH SUNDAY...
.Wednesday night...VFR with NW gusts around 20KT in the evening.
.Thursday through Friday night...VFR.
.Saturday...VFR. SW winds G15-20KT.
.Saturday night-Sunday...VFR. NW winds G20KT.

&&

.MARINE...
Winds subside through midnight for all waters, but SCA will
continue for the ocean waters as seas will be slower to subside.
A cold front will be moving east of the forecast waters early
Wednesday as high pressure builds to the west, with marginal SCA
conditions on ocean waters and SCA gusts likely all waters in
its wake.

5 to 6 ft waves on the ocean waters on Thursday will continue as a
northwest flow shifts to the west-southwest. Waves will diminish
Friday, generally coming down below 5 ft for most areas on the ocean
by Friday afternoon. Waves increase again on the ocean late Friday
night as a southwesterly flow sets up ahead of an approaching cold
front, diminishing Saturday night.

Winds should generally remain below 25 kt until Sunday afternoon as
a northwest flow strengthens behind the passage of a cold front.
Winds should remain above 25 kt from Sunday evening throughout the
rest of the long term.

&&

.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 6 AM EST Thursday for ANZ350-353-
     355.
     Small Craft Advisory until 2 AM EST Wednesday for ANZ330-340.

&&

$$
SYNOPSIS...CB
NEAR TERM...CB/NV
SHORT TERM...CB
LONG TERM...JP
AVIATION...Goodman
MARINE...CB/JP/NV
HYDROLOGY...CB/JP


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